ANDREW HUBERMAN: Welcome to
the Huberman Lab podcast, where we discuss science
and science-based tools for everyday life. [MUSIC PLAYING] I'm Andrew Huberman,
and I'm a professor of Neurobiology
and Ophthalmology at Stanford School of Medicine. Today we are
discussing caffeine. Caffeine is one of the
most widely used substances on the planet. Estimates are that more than
90% of adults and as many as 50% of kids that is
adolescents and teenagers use caffeine on a daily basis. Caffeine is an amazing molecule. Most people are familiar
with caffeine's ability to increase alertness and
to reduce our feelings of sleepiness and fatigue. And indeed, it does that. But what most people
are not aware of is that caffeine acts
as a strong reinforcer. What I mean by reinforcer
is that, when caffeine is present in a drink or food– and yes, indeed, caffeine
is present in many foods even unbeknownst to us.
When it's present
in drinks and foods, we actively come to like those
foods and drinks more than if caffeine were not contained
in those foods and drinks. So it reinforces our liking of
particular foods and drinks. And indeed, it even
reinforces our liking of the containers
they are consumed from and the company we keep when we
consume foods and drinks that contain caffeine. That is, caffeine is
not just a stimulant. Caffeine is a reinforcer. And it's a reinforcer that
plays an active role in almost everybody's daily life.
We can say that with confidence
because, as I mentioned a moment ago, more than 90% of
people are consuming caffeine. And most people think that they
consume caffeine because it makes them feel more alert. But there are many reasons
why you're consuming caffeine. And I'm not going to tell you
that consuming caffeine is necessarily bad. In fact, today, I'm going
to tell you about many of the positive health
benefits of caffeine, including
neuroprotective effects, antidepressive
effects, and certainly performance-enhancing effects,
both for mental performance and for physical performance.
Now that said, there are
certain situations in which you want to avoid caffeine, and
there are certain people who might opt to avoid caffeine. That's especially the case
when one thinks about caffeine not just as a stimulant
but as a reinforcer. In fact, caffeine is
such a strong reinforcer that, if even tiny
amounts of caffeine are present in certain
foods and drinks, you will very quickly
come to prefer those foods and drinks over
other choices, which can be a good thing
or a bad thing, depending on what sorts
of food and drink choices you're trying to make. So today, I'm
going to inform you about how caffeine works
at a mechanistic level. I promise to do
that with a minimum of nomenclature and such
that, even if you don't have a background in
biology, you will be able to digest that
information easily.
And then I'll tell you how to
use caffeine to your advantage or conversely how to avoid
caffeine at certain times to your advantage. So today's episode will focus
both on mechanisms and tools that is the use and
leverage of caffeine to improve mental
health, physical health, and performance. Before we go any further
into today's discussion, I want to tell you about some
recent results about a molecule that's found in certain
caffeinated beverages and that has been proven to
be very useful for both weight loss, mental performance, and
controlling blood sugar levels. And that's GLP-1 or
glucagon-like peptide 1. Glucagon-like peptide 1 is
found in the brain and body. It acts both on
the brain and body.
It does many different things. But one of its primary
effects that's been discovered is to reduce hunger. And it does that in two ways. It does that by
activating certain neurons in your hypothalamus. So that's a brain region that
controls hunger and satiety. It makes us feel full at
the level of the brain, so it makes us feel
sated, that is. And it actually
makes us feel full. It turns out that GLP-1 acts
on certain receptors in the gut to make us feel as if
we've ingested enough food. It doesn't necessarily
make us feel as if our gut is distended,
but it makes us feel full. That's really interesting
because, if you think about it, when we eat,
our stomach fills up, obviously. And that information has to be
communicated to the brain such that the brain can then send
satiety signals that actually shut off our hunger. And believe it or not,
the brain actually activates signals
to reduce the desire to chew when our
stomach is full.
And GLP-1, as I mentioned,
works on the brain to create these feelings of
satiety as if we've had enough and to reduce our
desire to eat more. And GLP-1 acts
directly on the gut to give us a slight sense of
fullness in the gut, which then is communicated to the brain. So really, there are
two parallel signals being sent when we have
GLP-1 present in our system. Now a little bit of
relevant history on GLP-1. It was actually discovered
in Gila monsters. These are these reptiles that
can go long periods of time without eating. And a very clever
scientist decided to study why it is that certain
animals like Gila monsters can go a long period of time
without ingesting anything. And it's because they produce
very large amounts of GLP-1. They isolate the
peptide from GLP-1, then they looked for the
analogous peptide in humans.
And it turns out
that does exist. And as I mentioned, it's
released in both brain and body to make you feel full and sated. Why am I telling you all this? Well, today we're going
to talk about caffeine. And there's one particular
caffeine source, which is yerba maté, and there
are some other forms of teas similar to yerba mate that
stimulate the release of GLP-1 significantly. There are also nowadays drugs
which are called analogues of GLP-1.
So these are drugs
that mimic or are identical to the kind of
GLP-1 that you would make. And those drugs are proven
to be very effective for the treatment of
certain forms of diabetes and for the
treatment of obesity, but they trigger
enormous amounts of GLP-1 pathway activation. So those are extreme cases
for people that are really struggling for weight loss. But the clinical trials and
the data that are out there in the general
population now are very, very promising for
GLP-1 analogues. Yerba maté tea, provided
it's not the smoked variety– and I mention that because a
number of people have cued me to the fact that yerba maté
teas come in smoked varieties and nonsmoked varieties. And the smoked
varieties are thought to perhaps be carcinogenic. That is, procancer-causing. So I advise people to avoid
smoked varieties of yerba maté tea. But yerba maté teas are known
to stimulate significant amounts of GLP-1 release. And so they can be effective
as a weight loss tool, mainly by blunting appetite. And again, they do that both
at the level of the brain and at the level of the gut. Now all of what I
just told you has been known for some
period of time, but there are new set of
findings that were just published in Cell Reports
Medicine, Cell Press journal, excellent journal– which indicate exactly
how it is that GLP-1 stimulates both satiety and
can trigger additional weight loss through other mechanisms.
And I find the mechanism to be
really interesting and actually really important, given
some other topics we've covered on this podcast before. So the basic finding
is that GLP-1, whether or not it's stimulated
through the release of analogue drug that one is prescribed
or by drinking yerba maté tea, for instance, and stimulate
release of your own so-called endogenous GLP-1, yes, it makes
you feel more full at the level of brain and body. But it turns out it also
stimulates thermogenesis.
Now thermogenesis is
the active utilization of more metabolic energy. And fat cells, in particular–
so-called beige and brown fat cells– are a potent source of
thermogenic activity in your body. The basic background is that
you have white adipose cells, so white fat cells. You have beige fat cells,
and you have brown fat cells. And the beige and brown
ones are fat cells that you actually want more of. They are not abundant
under your skin. They're abundant really
around your clavicles and your upper neck.
They are the ones
that generate heat. And the beige and
brownness of them is actually the consequence of
having a lot of mitochondria in those cells. When GLP-1 is elevated
in your system, it turns out that
it communicates to those white fat cells
and helps convert them into beige and brown fat cells. That is, it takes fat
cells that are not doing anything useful for you
except being stored energy. And I think most
people out there would like to have fewer of
those white adipose cells. There are few of you
out there that actually need more of them that
are too thin, too lean, but most people are suffering
from having too many of these white adipose cells. Well, when you ingest yerba maté
tea or you were to take a GLP-1 analogue or stimulate GLP-1 in
any number of different ways, yes, you stimulate
increased satiety, but you're also stimulating the
conversion of these white fat cells into beige
and brown fat cells, which makes you more thermogenic
and over time raises your basal metabolic rate.
So you're burning more
calories even at rest. It also makes you
feel as if you're more comfortable in colder
environments at rest. This is very much the same
as the mechanism that's induced when you were to,
say, take a cold shower or do regular ice baths or
get into cold water regularly. That, too, stimulates the
conversion of white fat cells to beige and brown fat cells. So I like these
findings very much because they provide a
mechanistic coherence. They provide that is a
really nice story as to how something like GLP-1 could be
so effective for weight loss. Yes, on the one hand,
GLP-1 is reducing appetite, and that, of course, will help
people maintain or lose weight. But it's also increasing
basal metabolic rate. And we now know how
that's accomplished.
It's likely accomplished
at least through this one mechanism by the
stimulation of conversion of these white fat cells,
which don't do much for us except as energy storage
units to these metabolically mitochondrial-rich beige
and brown fat cells, which you can think of as
sort of the oil in the candle that allows your furnace, your
metabolism to burn at a higher temperature and a higher rate. So that's the mechanism. And the basic tool
takeaway is that, if you are somebody who's
interested in losing weight and you want to leverage
the GLP-1 pathway, drinking a cup or two of yerba
maté tea early in the day would be a great way to
stimulate GLP-1 release. There are other ways to
stimulate GLP-1 release. You can get it through
certain forms of exercise. In particular, fasted exercise. This is actually a vote in
favor of fasted exercise. There's a debate as
to whether or not fasted cardio burns more
fat than nonfasted cardio. And the data basically say
no, it doesn't really matter. But that doesn't really
take into account the longer arc of things
like GLP-1 release, so that needs to be
taken into consideration.
So you could do fasted cardio. You could drink yerba maté tea,
keeping in mind that yerba maté tea does contain caffeine. We'll talk more about the
specific forms of stimulants including caffeine
that maté has. But maté would be a great way
to stimulate GLP-1 release. And then, of course, for those
of you that are interested in more robust
activation of GLP-1, then perhaps you might want
to consider some of the new prescription GLP-1 analogues
that are out there. But that's a more severe
stimulus for GLP-1, of course. And for everybody, regardless
of whether or not you're trying to lose weight, gain
weight, or maintain weight, I think we're going to be
hearing a lot more about GLP-1 analogues and drinks and
supplements and things of that sort that stimulate GLP-1 in
the very near future because it does appear to be a very
important biological mechanism.
Before we begin, I'd
like to emphasize that this podcast is separate
from my teaching and research roles at Stanford. It is, however, part
of my desire and effort to bring zero cost to
consumer information about science and
science-related tools to the general public. In keeping with
that theme, I'd like to thank the sponsors
of today's podcast. Our first sponsor is Levels. Levels is a program
that lets you see how different foods affect
your health by giving you real-time feedback on your
diet using a continuous glucose monitor.
The blood glucose or blood
sugar is a critical aspect of your immediate and
long-term health and, indeed, your feelings of vigor and
mental clarity and well-being at any moment. One of the key things is to know
how different foods and food combinations and
timing of food intake is impacting blood glucose. And with Levels,
you're able to assess all of that in real time. I tried Levels,
and what it taught me, for instance, was that
I can eat certain foods at certain times of day. But if I eat them at
other times a day, I get a blood sugar crash. It also taught me,
for instance, how to space my exercise
and my food intake. Turns out for me exercising
fasted is far more beneficial. That's something I
learned using Levels, and it's completely transformed
not just the spacing and timing of my diet and
exercise but also use of things like the sauna
and other activities.
It's been a tremendous
learning for me that's really shaped an enormous
number of factors in my life that have led to me feeling
far more vigorous with far more mental focus and physical
strength and endurance. So if you're interested in
learning more about Levels and trying a continuous
glucose monitor yourself, go to levels.link/huberman. Again, that's
levels.link/huberman. Today's episode is also
brought to us by Eight Sleep. Eight Sleep make smart mattress
covers with cooling, heating, and sleep-tracking capacity. I've talked many
times on this podcast about the critical relationship
between sleep and body temperature. That is, in order to fall
asleep and stay deeply asleep throughout the night,
our body temperature needs to drop by
about 1 to 3 degrees. And conversely, when we
wake up in the morning, that is in large part
because of our body heating up by 1 to 3 degrees. Now people have different
core body temperatures, and they tend to run colder or
hotter throughout the night.
Eight Sleep allows you
to adjust the temperature of your sleeping
environment so that you have the optimal temperature
that gets you the best night's sleep. I started sleeping on
an Eight Sleep mattress cover about eight months
ago, and it has completely transformed my sleep. I sleep so much deeper. I wake up far less during the
middle of the night, if at all.
And I wake up feeling far
better than I ever have even after the same amount of sleep. If you want to try
Eight Sleep, you can go to eightsleep.com/huberman to
save up to $400 off their Sleep Fit Holiday Bundle, which
includes their new Pod 3 Cover. Eight Sleep currently
ships in the USA, Canada, United Kingdom,
selected countries in the EU, and Australia. Again, that's
eightsleep.com/huberman. Today's episode is also
brought to us by ROKA. ROKA makes eyeglasses
and sunglasses that are of the absolute
highest quality. The company was founded by
two all-American swimmers from Stanford. And everything about ROKA
eyeglasses and sunglasses were designed with
performance in mind. I've spent a lifetime working on
the biology, the visual system. And I can tell you that
your visual system has to contend with an enormous
number of challenges in order for you to see clearly,
for instance, when you move from a sunny area
to a shady area and back again, whether or not
you're looking at something up close or often to the distance.
ROKA understands the
biology of the visual system and has designed their
eyeglasses and sunglasses accordingly, so you always
see with perfect clarity. ROKA eyeglasses and
sunglasses were initially designed for activities
such as running and cycling. And indeed, they are
very lightweight. Most of the time I
can't even remember that they're on my face. They're so lightweight. But the important thing to
know about ROKA eyeglasses and sunglasses is
that, while they can be used during
sports activities, they also have a
terrific aesthetic, and they can be used just as
well for wearing to work or out to dinner, et cetera. If you'd like to try ROKA
eyeglasses and sunglasses, you can go to ROKA. That's R-O-K-A.com and enter the
code Huberman to save 20% off on your first order. Again, that's Roka, R-O-K-A, dot
com and enter the code Huberman at checkout. The Huberman Lab
podcast is now partnered with Momentous supplements. To find the supplements we
discuss on the Huberman Lab podcast, you can go to
livemomentous, spelled O-U-S, livemomentous.com/huberman.
Huberman. And I should just
mention that the library of those supplements is
constantly expanding. Again, that's
livemomentous.com/huberman. Let's talk about caffeine. So as I mentioned
earlier, caffeine is consumed by basically most
all adults every single day and consumed at very
regular times each day. In fact, if you were to take
a look at your caffeine intake or the caffeine intake
of somebody close to you, what you
would realize is that they don't do so well if
their caffeine intake arrives even 10, 20, or 30 minutes past
their expected or usual intake of caffeine. That's pretty
remarkable, and it brings to mind ideas that
we are all, quote unquote, "addicted to caffeine"
or that caffeine is somehow bad.
I'm certainly not going to make
the argument that caffeine is bad. First of all, I'm a
regular caffeine user. I wouldn't call myself
a caffeine abuser, but I am a regular
caffeine user. And caffeine is known to
have certain health benefits. I listed off a few
of them earlier, but I'll mention those again
now before going forward. Caffeine is known to have
certain neuroprotective effects. And that is because
of its ability to increase neuromodulators,
such as dopamine, but also other
so-called catecholamines like norepinephrine. If you don't know
what those names mean, these are molecules that
increase levels of alertness, motivation, and drive. And so then therefore not
surprisingly the large scale analyses of the relationship
between depression and caffeine shows that, provided people are
not drinking so much caffeine, that it makes them
overly anxious, that regular intake of
caffeine is inversely related to levels of depression.
So it may have some
antidepressant effects. And those could be
direct or indirect. What do I mean by that? Well, you can imagine that if
people are ingesting caffeine and they are more motivated
to do work and pursue quality social
interactions, then the probability that they will
have depression could be lower. It could also be that
there are direct effects on the chemical systems
of the brain that relate to mood and well-being
that could offset depression. It is not clear whether
or not the effects of caffeine in
countering depression are direct or indirect. Nonetheless, there's
a relationship there, and it's an interesting
and positive one. Or I should say
negative correlation, positive effect overall on mood
and well-being, to be exact. Now it's also the
case that caffeine can improve mental performance
and physical performance.
This has been demonstrated in
tens of thousands of studies. I will review a few studies
on this, in particular, today. But to just give
you a sense of how caffeine works at the level
of its timing and impact on mental performance and
physical performance, when we ingest caffeine,
provided that we don't have a lot of food in our stomach
and that our blood sugar isn't particularly high, generally,
we experience an increase in alertness within
about five minutes. And that increase in
focus and alertness peaks around 30 minutes after
ingestion of caffeine and persists for as
long as 60 minutes. Now this is assuming that one
takes caffeine in pill form or drinks the entire
caffeine drink within a short period of time. But a little bit
later, I'll talk about how you can consume
caffeine at regular intervals while doing mental work or
physical work in a way that can further increase
mental performance and physical performance. But let's just touch
on what caffeine intake really does
for mental performance and physical performance.
Perhaps the most robust
finding across all of the studies
that I've examined is that caffeine reduces
our reaction time. That is, it improves
our reaction time. It doesn't make it longer. It makes it shorter. So for instance, in
a laboratory study where people were asked to hit
a lever every time they hear a tone, you can greatly reduce
the time between the tone and the pressing of the lever
if people ingest caffeine about 30 minutes before
they do that task. Now that seems like
a trivial task, but this is also seen in the
domain of sports performance and even in cognitive
performance, where people have to arrive
at a particular answer to a question. And the answer to
that question has to be pulled from
their memory banks within their brain,
their hippocampus, for instance, a brain
structure involved in memory. And if you are asking
people, for instance, to remember the capitals of
different states or cities or to remember certain
historical facts, they will do that at
a particular rate.
But if they've ingested
caffeine within the hour prior, their ability to
recall that information is much, much better. They are faster, and
it does not appear that accuracy is reduced. In fact, in many cases,
accuracy is enhanced. And that's because caffeine
both works on the reaction time systems of the brain and body. I'll talk about the mechanisms
for that in a little bit. But it also stimulates
certain neurotransmitters and so-called neuromodulators
within the brain and body that give the neural
circuits in the brain that are associated with
learning and memory a lower threshold to activation. What does that mean? That means that we are
better able to access the brain circuitry involved
in learning and memory when we have a certain amount
of caffeine circulating in our system.
So this makes
caffeine an incredible performance-enhancing compound. And I could give you
tens of thousands of examples of this in humans. But before I do that,
I want to just touch on what we know about the
existence of caffeine in nature and what the existence
of caffeine in nature and its effects on other
animals tells us about what caffeine does in humans. Because as I alluded to
earlier, what caffeine is doing for us is not just
making us more alert, improving our memory, improving
our reaction time, and so on. It's actually acting as
a powerful reinforcer of experience. And it's acting as not
just a powerful reinforcer of the caffeine-containing
drink that we drink but also the mug that
it's contained in, plus the person that
we might be sitting across from when we consume
that caffeine, and so on and so forth.
If it's a little
bit hard for you to conceptualize
what a reinforcer is and why I'm calling
it a reinforcer, let me spell it out in
three specific ways. We often hear about
the word reward, and we think, OK, if
we do certain things and we like the outcome,
then those certain things are rewarded. Right? If we're doing something,
we receive praise. The praise is the reward. And therefore, we
are more likely to do that thing in the future. In fact, a lot of
parenting is like that. And a lot of life is like that. However, when we
hear the word reward, we often think about something
that feels good to us. And certainly, if we've worked
hard and we get some praise, that's natural for the
praise to feel good to us. Or for instance, if
we work very hard and we get a certain outcome– a trophy, a financial outcome,
a degree outcome, recognition, et cetera– all of those
can act as rewards, but those are all
conscious rewards.
We are aware that
they are happening. Reinforcers are a little bit
different because the word reinforcement can apply to
conscious rewards of the sort that I just described,
but there are also many ways in which
caffeine stimulates the release of chemicals in our
body that act as reinforcers. But those reinforcers
are subconscious. That is, we are
not aware that they cause this preference
for the activities that cause their release. So the study I'm about
to describe beautifully, I believe,
encapsulates how is it that humans came
to consume caffeine and why caffeine exists in
nature and the powerful effects of caffeine as a reinforcing
agent both in animals, insects, and in you and me. And the title of the
paper is "Caffeine and floral nectar enhances a
pollinator's memory of reward." Keep in mind that caffeine
is made from plants. Some of you will say, duh,
but I think some of us don't realize that the reason
why there is caffeine in coffee is because coffee
comes from a plant.
It's a coffee
bean, certain teas, which, of course, are
plants that people brew. Caffeine is contained in those
teas, such as yerba maté. Well, why would this
bitter substance– because, in fact, caffeine is quite
bitter in high concentrations. Why would this bitter
substance be something that insects or animals
would want to consume at all? It turns out that,
in most plants, caffeine is present in
small enough quantities that insects and other animals–
and in fact, we can't actually taste the caffeine. If I were to give you a
little bit of pure caffeine, yes, it would be a
stimulant for you, but you would say
that it tasted awful. It's in a category of compounds
that would strongly stimulate the bitter receptors
on your tongue and would make you
cringe and pucker and essentially walk away from
whatever it is that contain that caffeine and from
the experience that contain that caffeine. Well, in nature, caffeine
is present in very low concentrations or is
masked by other flavors within flowers,
beans, and plants.
And what this paper
really points to is that caffeine
in nature is acting as a reinforcer for bees that
are consuming different nectar. So the way that it works
is that bees, of course, go from flower to flower, and
they are consuming the nectar. They are bringing nectar
and pollen back to the hive, and that provides critical
nourishment for the bee colony.
The bees are foraging in a
way that includes information about color, in particular,
ultraviolet color, things that we can't see
but they can see, because they have different
photoreceptors than we do. And what the study shows is
that plants and nectars that contain very small
amounts of caffeine are the preferred
sources of food for bees. And the study is
beautiful because they were able to confirm that they
could mask the caffeine taste. So they know that the
bees are not preferring the taste of caffeine. But what they do is
they pair caffeine with different food
sources for the bees, then they remove the caffeine. And what they find is that
the bees very strongly prefer flavors that
contain caffeine, not because they could taste the
caffeine but rather for the way that those caffeine-containing
flavors made the bees feel.
So how do those
caffeine-containing flavors make the bees feel? The same way that
they make you and I feel, a little bit
more alert and thereby able to do more work. For the bee, the more
work is the consumption of more food, which then has
a further reinforcing effect. So what we're really
talking about here is the fact that A, caffeine
exists in nature, in plants. It exists in concentrations that
are very low, so low, in fact, that they are not detectable to
the taste receptors of insects, and, in many cases, to the
taste receptors of humans.
And, of course, there
can be high levels of caffeine in a plant. But if the plant also
contains compounds that mask the
flavor of caffeine, well then, those plants
are going to essentially be even stronger reinforcers
for the flavor of the plant, OK? So now we're talking
about strong flavors plus strong neurostimulant
effects of caffeine. And the most
important point here is that all of these effects
of caffeine are subconscious. It is not because the bee or
you likes the taste of caffeine. In fact, most people, when they
take their first sip of coffee, they find it taste bitter
and kind of noxious. They don't like it.
You may not even remember that
because it happened so long ago and because caffeine is
such a strong reinforcer that very quickly you come
to like the taste of coffee. You might even come to like
the feeling of your mug in your hand. You might even come to
like the smell of coffee and so on and so forth. And that's because
caffeine stimulates the release of certain
neurochemicals in the brain, in particular, dopamine
and acetylcholine, two neuromodulators
that increase our focus and alertness and our
feelings of well-being. A little bit later,
I'll tell you that caffeine stimulates
the release of dopamine in a way that's
very much distinct from the classical
dopamine pathway associated with addiction and reward.
In fact, we can
think of caffeine as having a somewhat privileged
access to the reward systems. I'll give you a bit of a
hint of where this is going. Caffeine stimulates the release
of dopamine and acetylcholine not within the classic so-called
mesolimbic reward pathway. That's just fancy nerd
speak for the reward pathways of the brain. They're associated with
things like sex and food and drugs of abuse, like
cocaine and methamphetamine. But rather, caffeine
seems to stimulate the release of dopamine in
the parts of the brain that are associated with
alertness and cognition, meaning the forebrain. This is very important. We have multiple dopamine
systems in the brain and body, and caffeine seems to
stimulate dopamine directly within the components of the
brain that are associated with clarity of
thought and well-being, but more so clarity of thought. Now, I'm also talking
about caffeine as a strong reinforcer in that
it makes you feel good overall. And it does.
And that suggests that it
also taps into the more classic reward pathway. But it does that in a very
interesting and frankly almost diabolical way. When we regularly
ingest caffeine, it stimulates the increase
in dopamine receptors at multiple sites throughout
the brain but, in particular, within the reward
pathways of the brain. So not the areas
of the brain that are associated with focus
and clarity of thought and cognition. It does that, but it
is also increasing the level of dopamine receptors
in the reward pathway.
And what that means is that,
for any dopamine that's released in response to
a positive experience, social experience, or any
number of the other things that can stimulate
dopamine release, there are more receptors,
more parking spots, if you will, for that
dopamine to arrive at and to exert its increases in
mood, increases in motivation, and overall feelings of
drive and excitement.
So there are four ways
that caffeine works that we need to understand. First of all, caffeine acts
as a reinforcing agent. It increases the
probability that you will return to and engage
in a certain activity or consume a certain
beverage or food. Second of all,
caffeine increases dopamine and
acetylcholine, which are both neuromodulators
in the forebrain, which helps us improve our ability to
think, to modify our rule sets. That is, to adjust
our strategies for different social
situations and mental demands and physical demands. And third, it increases
the number and efficacy of dopamine receptors in the
reward pathways of the brain. That is, it makes things
that would feel pretty good feel even better.
And fourth, caffeine
acts as an antagonist to adenosine, which offsets
the sleepiness that we would otherwise feel from the
accumulation of adenosine that occurs as we are awake
for more and more hours throughout the day. So let's talk first
about caffeine as a reinforcing agent. Again, this was first most
beautifully demonstrated in this study on honeybees
where the bees prefer nectars that contain caffeine. And that all makes
perfect sense in terms of the ecology of bees and
flowers that contain nectar. There's an advantage, at
least in terms of adaptation, that the flower benefits because
of distribution of things from the flower, which is good
for the flowers and the bees benefit, because
they're getting food.
And so there's a kind
of a symbiosis there. But with humans, we're consuming
caffeine-containing beverages for our sake. I don't think we
have it in mind, nor do the bees have
it in mind, frankly, that we're trying to
preserve the plants that provide the caffeine. I think we would all suffer,
or I should say 90% of adults would suffer greatly if all
the caffeine-containing coffee and tea plants were
gone, certainly. But most of us are not
consuming coffees and teas and caffeine-containing
foods because we're thinking about the
plants they come from and we want to
help those plants. We're thinking about how
we want to help ourselves. And yet the point of the
reinforcing effects of caffeine are that they are
largely subconscious. We are not aware of them.
Now you might say,
no, that's not true. When I drink caffeine, it
makes me feel really good. So I'm aware that it
makes me feel good. In order to illustrate how
reinforcement really works, let me give you the
counter example, which would be an aversive agent. So we have reinforcing agents
and we have aversive agents. Let's say that there were
compounds in nature that exist in plants that are aversive. And indeed, they are. And let's say that
these compounds were present at such
low concentrations that you couldn't taste them. Let's say you wake
up in the morning and you go to your
refrigerator and you open it up and you are thirsty,
and so you reach for a nice rich red-containing
beverage in a glass jar.
Maybe it looks like
cranberry juice or something of that sort. Or even a nice clear
glass of water. It looks like a jug of
water or a glass of water, and you drink that. Taste fine to you. Maybe even tastes great to you. And then let's say
about 30 minutes later, you feel a little queasy,
you feel a little off, you feel like going
back to sleep, you just don't feel very good. You don't know why,
but your nervous system is a predictive machine, and it
has a process in which it back integrates. Or I should say
integrates backwards into your immediate experience
that preceded that not so good feeling. We can reliably say that there
is a much lower probability that the next day
when you wake up that you would reach
for that same beverage or for that same container even. And maybe if you're in
a novel environment, maybe you're staying in an
Airbnb or a hotel or something of that sort, you might even
find that you don't really like the kitchen in which
you consume that beverage in the first place.
And you don't know why. And unless you got very,
very sick the day before, it's unlikely that you would
have such a strong response that you would entirely avoid,
for instance, water or glass jars containing
liquids, et cetera. Let's say you went back
to the refrigerator and you consume a beverage
again and you just didn't feel so well,
you felt less good than you normally would. Well, even without
any ability to taste what's in that beverage and
even without any understanding of what was happening to
you at a conscious level, there is a very,
very high probability that you will avoid drinking
that particular beverage and certainly at that location
and in the same volume in the subsequent days.
That's just the way that
aversive agents work. And they work by way
of activating neurons in the gut that communicate with
areas in the brain that give us this feeling of queasiness. And for some of
you hearing this, that pathway and
that association with times in which you felt
queasy and as if you wanted to vomit is so powerful that
you might even be feeling some of that symptomology now. For certain people that's going
to be increased salivation which precedes vomiting,
we know that there's a class of neurons
in the brain relate to an area called area postrema
that actually stimulates vomiting. And if I keep
talking about this, I'll probably feel
like I want to vomit, so I'm going to move on
from this in a moment.
So when we ingest
caffeine-containing beverages and foods, it's the
exact opposite scenario as to what I just described. Caffeine, as a
reinforcer, makes us feel slightly better
or a lot better in the immediate minutes and
hours after we ingest it. So it's acting as
a reinforcing agent not just while you are under
the effects of caffeine but for the things that preceded
the ingestion of caffeine, which is why you
return again and again to caffeine-containing
beverages, such as coffee and tea or maybe even foods
that contain caffeine, even if the taste of those
foods is not something that you would otherwise
consider, especially delicious. In fact, most people when they
take their first sip of coffee or tea or other
caffeine-containing beverage, they find it to be very bitter. And that's not because
of the taste of caffeine. It's because of the taste of
the beverage itself independent of caffeine.
However, when caffeine
is present in there, they come to prefer that
taste over most all tastes. In fact, they will, as
I mentioned earlier, will invest a lot of financial
resources and time and energy to make sure that they
get that beverage. What they're trying to make sure
is not that they get that taste but that they get the caffeine. It is that positively
reinforcing. And the taste therefore takes on
new significance, new meaning, and we come to associate
it as positive. And in fact, most of
us, including myself, love the taste of espresso,
love the taste of coffee, love the taste of yerba maté
even if the initial taste, the very first time that
we consume that beverage, was either neutral or negative. And that is all because of
the reinforcing properties of caffeine. And then, of course, there
are the more direct actions of caffeine. That is, the faster
actions of caffeine. And just to list those off
again very briefly so that you have them in mind going
forward, caffeine also increases the release of
dopamine and acetylcholine, both of which are
neuromodulators in the forebrain, which
increases clarity of thought and your ability to rule
switch, your ability to move from one
context to another and change and understand
the rules of engagement, social engagement, physical
engagement, mental engagement, and so forth.
And as I mentioned
before, caffeine also increases the number of
dopamine receptors in the reward pathway, such that any good
thing that happens to you. Any positive experience
that you have will have a more potent effect
on your feelings of well-being. And last but certainly
not least, caffeine acts as an adenosine antagonist. It reduces your feelings
of lethargy and fatigue and your desire to
sleep by parking in the receptors for
adenosine and not allowing adenosine to have
its pro-sleepy, if you will, effects on your brain and body. I'd like to take a quick
break and acknowledge one of our sponsors, Athletic Greens. Athletic Greens, now called AG1,
is a vitamin mineral probiotic drink that covers all of your
foundational nutritional needs. I've been taking Athletic
Greens since 2012, so I'm delighted that they're
sponsoring the podcast. The reason I started taking
Athletic Greens and the reason I still take Athletic Greens
once or usually twice a day is that it gets
me the probiotics that I need for gut health.
Our gut is very important. It's populated by
gut microbiota that communicate with the brain, the
immune system, and basically all the biological
systems of our body to strongly impact our
immediate and long-term health. And those probiotics
and Athletic Greens are optimal and vital
for microbiotic health. In addition, Athletic
Greens contains a number of adaptogens,
vitamins, and minerals that make sure that all of my
foundational nutritional needs are met. And it tastes great. If you'd like to
try Athletic Greens, you can go to
athleticgreens.com/huberman, and they'll give you five
free travel packs that make it really easy to mix up
Athletic Greens while you're on the road, in the
car, on the plane, et cetera.
And they'll give you a year
supply of Vitamin D3K2. Again, that's
athleticsgreen.com/huberman to get the five free travel
packs and the year supply of Vitamin D3K2. I'd like to just briefly
talk about adenosine and some of its molecular features. And again, if you don't have
a background in biology, don't worry. I promise to make this
very clear to everyone. First of all, caffeine is
what's called a methylxantine. It's a plant alkaloid. That's why caffeine
itself is very bitter. Again, if I were to give
you just the tiniest little bit of pure
caffeine, you would find it to be extremely aversive. So these plants that have
snuck small enough amounts of caffeine into
them or that have masked the flavor of
caffeine with other flavors such that bees and humans
want to consume them, while we don't know what
plants think, it does seem very diabolical
and very clever in that we are seeking out these
caffeine-containing plants, beverages, and foods even
though caffeine itself is this alkaloid that
is very, very bitter.
Methylxantine–
that is caffeine– binds to adenosine receptors. And there are really two
types of adenosine receptors. There are these so-called A1
receptors and the A2 receptors. And they are present in
different parts of the brain and body at different levels. We don't have to get too
far into receptor subtypes. More importantly
to understand is that adenosine makes us feel
tired because of the way that it taps into
the ATP pathway. The ATP pathway is central to
energy production and feelings of overall energy in
our brain and body in all cells and organ systems.
When caffeine binds to
adenosine receptors, it prevents adenosine
from breaking down certain components of the
energy production pathway. And the net consequence of
that is increased cyclic AMP. So basically, when
we ingest caffeine, we are biasing
our system towards the pro-energetic aspects
of these cellular pathways. Now it's really important to
understand that, in biology, even if you block a
receptor or you prevent the activity of an enzyme and– at least, in this
case, you end up with more cyclic
AMP, more energy. You're not really
getting more energy. You're actually borrowing
energy against an overall system that is frankly nonnegotiable. What do I mean by that? Well, let's say that you were
to wake up after six or eight hours of sleep and to
drink a lot of caffeine and keep drinking caffeine
throughout the day blocking those adenosine receptors. Yes, you'll offset fatigue. You'll offset sleepiness
because that adenosine simply can't function. But at the point where the
caffeine becomes dislodged from the adenosine
receptors, you will have a massive glut,
a backlog of adenosine, and you will feel
extra, extra sleepy. So really, there's no
way to create more energy in your system.
Really, what you're
doing is you're changing the timing in which
the sleepy signals and the more energetic signals are arriving. And this is really important
to understand as the backdrop to the various tools
that we're going to get into next, in which you
can use caffeine for enhancing mental performance and
physical performance and other aspects of health. But it's very important
to understand this concept that, when you wake up in the
morning provided that you slept well and enough
the night before, your levels of adenosine
will be about as low as they will ever be.
Actually, in order to get
your adenosine levels really bottomed out, you want to avoid
caffeine in the first 90 to 120 minutes after waking. We'll talk about why that
is because it turns out there's a way to
completely clear adenosine out of your system in the
hour or so after waking. But for most people,
adenosine levels are going to be
close to their lowest after a good night's sleep. But there's really no
negotiating the accumulation of adenosine that's
going to occur and going to bias you towards
feeling more sleepy than you would. Otherwise, that's going to
occur throughout the day.
There's really no way
to eliminate adenosine. All you can really do
is block its function. So it's sort of like borrowing
energy against the fatigue that you will inevitably feel. Now this actually
has a very important socioeconomical relevance. Before caffeine was regularly
consumed by human beings, we were really slaves
to the light/dark cycle. And this was especially
true before the presence of artificial lighting. But even before the advent
of artificial lighting, humans were largely constrained
to the outside light/dark cycle. We need to be active during the
day and working during the day, and we need to be
asleep at night. Caffeine allows us
to divorce ourselves from that circadian cycle. Circadian just
means about 24 hour. Caffeine allows us to do
that at least somewhat by way of increasing our alertness.
That is, spiking our
alertness at various times throughout the day
and even at night. This is how we can have
shift workers, for instance, that can sleep during
the day and then drink a strong cup of
coffee at 8:00 PM and then work into the night. That ability completely
transformed our society. Now, of course, the
healthiest schedule– and we know this with certainty. The healthiest schedule
for brain and body is going to be alert during the
daytime and asleep at night. There's no question about that. Shift workers run into all
sorts of health problems. And thank you shift workers
for doing the important work that you do. We need you. Air traffic controllers,
paramedics, firefighters, police officers, et cetera. But we know that there are
serious health consequences, negative health consequences,
that is, for shift workers. But for most people out
there, about 95% of people follow a typical schedule. They're awake during the
day and asleep at night. And yet it used to
be before the advent of caffeine-containing
beverages that, if you were sleepy in the
afternoon, you either had to take a nap or
battle that sleepiness, that your activity rhythms
and your sleep rhythms were governed by these circadian
changes in availability of sunlight and when you slept.
And you just didn't
have the ability to ingest a beverage
that would increase your levels of alertness
because you block adenosine. So this is important
to understand that, nowadays,
we certainly live in a time in which we use– in fact, 90% or more of
adults and half or more of adolescents and
teenagers use caffeine as a way to negotiate
with, to borrow against this natural pattern
of adenosine making us sleepy. But again, you're
just offsetting the effects of sleepiness
that adenosine causes. You can't eliminate
the adenosine entirely. The important point
is that adenosine as a pro-sleep molecule
is a nonnegotiable aspect of your biology. In fact, it's so nonnegotiable
that, every 24 hours, you are going to release
adenosine, and you're going to release adenosine in
direct proportion to how long you've been awake.
So the longer you've
been awake, the more adenosine circulating
in your system. There are really only a handful
of ways to completely clear out adenosine. The major one
being to get sleep. The other is to take a short
nap, which, of course, is sleep, but it's shallow sleep. Or non-sleep deep
rest, so-called NSDR, has been shown to reduce
levels of adenosine. And there are certain things
such as viewing morning sunlight, which because of
its effects on cortisol, can quote unquote,
"clear out adenosine." We'll talk about this in
more detail in a few minutes. And there's also evidence that
certain forms of exercise, provided that it's
brief and intense, can also reduce adenosine,
not just block its effects. Now that we've talked about some
of the incredible mechanisms by which caffeine changes
our experience of life, increases alertness
and mood, et cetera, I want to talk about the
use of caffeine as a tool.
Now caffeine is a very
potent and useful tool for enhancing mental
health, physical health, and performance. But there are certain
considerations one has to keep in mind,
in particular, dose. Now, first off,
not everybody will respond to the same dose
of caffeine the same way, but we can reliably say
that your body weight is a good measure by
which you can estimate what a healthy, useful
dose of caffeine would be. So for most people,
ingesting 1 to 3 milligrams of caffeine per
kilogram of body weight is going to be the
range in which caffeine can have positive effects
without making us feel overly anxious and give us that
feeling that we're jumping out of our skin and
turn the otherwise positive experience of
caffeine into an aversive one.
For those of you that aren't
familiar with thinking in terms of kilograms and
normally think in pounds, I'll just quickly give you
some general estimations that, for instance, 100
kilograms equals 220 pounds. So for me, I weigh
100 kilograms. That means that 1
to 3 milligrams– again, milligrams,
thousandth of a gram. 1 to 3 milligrams of caffeine
per kilogram of body weight would mean for me. I could safely ingest 100 to
300 milligrams of caffeine in a single dose,
in a single drink, if that's the way
I'm consuming it, or pill form if that's the
way that I'm consuming it. And it's very likely that
that will be a tolerable dose. However, if you are
not somebody that's accustomed to drinking
caffeine on a regular basis, I suggest you start on the
lower end of that 1 to 3 milligrams per kilogram
of body weight range.
So for instance,
if you're somebody who weighs 50 kilograms, that's
approximately 110 pounds. And you would be
pretty comfortable ingesting somewhere between 50
and 150 milligrams of caffeine. So what I recommend is that
people who are considering using caffeine as a tool or who
are already ingesting caffeine, start to think about
the dosage of caffeine that you are ingesting
or plan to ingest and the timing in which
you ingest that caffeine relative to certain tasks
throughout your day, your waking, and your sleep.
And we'll talk about
that in just a moment. But the first step for
you is to figure out how much you weigh
in kilograms and then to go to that number of 1
to 3 milligrams of caffeine per kilogram of body weight. And that's a good
range in which you might want to explore
the use of caffeine in a single application,
meaning a single dose. Now, I do realize that
some people out there are drinking coffee all day long
or having coffee in the morning and again in the afternoon. What I'm referring to here
is the ingestion of caffeine in a single bout, right? 1 cup of coffee or 2 cups
of coffee, for instance, to achieve that 100
to 300 milligram range if that's what's
appropriate for your body weight.
But to avoid any confusion,
when I talk about dosage of caffeine, what I'm
really talking about is not the total amount of
caffeine ingested per day. I'm talking about
the total amount of caffeine ingested in one
sitting or setting, that is. And if you're somebody who's
drinking caffeine multiple times throughout the day, you
can imagine– for instance, let's say the
appropriate dose for you in order to get an enhancement
in mental performance or physical performance
is 200 milligrams. And you are somebody who's
doing some work in the morning, and you want to have
that lift in the morning to be able to focus better. And you're doing some physical
exercise in the afternoon or vice versa that you
would ingest 200 milligrams of caffeine at two
separate times per day separated by about four hours.
Now you don't have
to separate them. You could put them two
hours apart, for instance. But we'll talk about half-life
of caffeine and so forth. Just keep in mind that, if
you're ingesting 200 milligrams of caffeine and that's the
appropriate dose for you based on your body
weight and then you are ingesting another 200
milligrams of caffeine an hour later, you are effectively
ingesting approximately 400 milligrams of caffeine,
which is going to start exceeding the dose
in which you can normally tolerate without feeling
anxious and jittery. With all of that
said, there is a range of tolerance for caffeine
that's based on two things. One is a preexisting disposition
that is whether or not your genetics and nervous system
and the backdrop of your life, how much stress
you're experiencing tends to make you feel more
anxious and alert and jittery before you ingest any caffeine.
And the other is how so-called
caffeine-adapted you are. We often hear about tolerance. Tolerance means
something very specific. It's the ability to ingest
more and more of something with a plateau that is a no
increase or an actual reduction in the effectiveness
of that thing. But here we're not really
talking about tolerance to caffeine. What we're talking about
is being caffeine-adapted. A simple way to
understand whether or not your caffeine-adapted or not
is that, if you drink caffeine and it tends to
increase your heart rate and make you feel more alert
and a bit more anxious, then chances are you are
not caffeine-adapted, provided the amount of caffeine
is within the healthy range for you, that is, the ranges
we talked about a moment ago. However, here's somebody
who drinks caffeine and you actually feel
alert and relaxed, chances are you are
caffeine-adapted. And so at various times
during today's episode, I'll talk about people
who are caffeine-adapted and people who are
not caffeine-adapted. We'll talk about the use of
caffeine every other day.
I know a few habitual caffeine
drinkers including myself, just the simple mention of
that probably sounds aversive. But there is actually
great utility to using caffeine every other
day as opposed to every day. But just keep in
mind that some people will drink caffeine and not get
much of a lift from it at all. Other people will
drink caffeine, and they will feel extremely
anxious even at dosages far lower than that 1 to
3 milligrams per kilogram of body weight range that
I described a moment ago. So you have to take into
account individual differences. That said, 1 to 3 milligrams of
caffeine per kilogram of body weight for a given sitting. For your morning coffee or
your morning yerba maté tea is a good range from
which to start.
And I do encourage you
to go online and look up the various beverages and
foods that you might be eating that contain caffeine. For instance, some people
are surprised to discover that the coffee that they get
from some of the more standard popular vendors out
there, the small coffee or the medium
coffee, for instance, can contain as much as 400 to
600 milligrams of caffeine. And the large
coffee that is often sold at those
commercial vendors can contain as much as 1 gram,
1,000 milligrams, of caffeine. Now you may be
adapted to that such that it doesn't make
you feel anxious, but if you wonder why
you feel irritable and you get a headache
when you don't get that caffeine or
that amount of caffeine at precisely the time that
you're used to getting it each day, that's because
you are consuming quite large quantities of
caffeine on a regular basis. So I do recommend whether or not
you drink soda or coffee or tea that you figure out
the source of that. OK, so figure out what
vendor you purchase it from, what kind of coffee,
and go online and spend a little bit of time
because the information is out there to discover
what levels of caffeine you're actually ingesting.
Now if you happen to be
ingesting more than 1 to 3 milligrams per kilogram
of body weight of caffeine, that's not necessarily bad. However, you do want to
be careful about ingesting very high levels of caffeine
over long periods of time in your life because there can
be issues that start to arise. In particular, a bias
towards higher levels of anxiety and depletion
of certain electrolytes. Because caffeine
is a diuretic can cause you to lose sodium and
other things of that sort.
And also just from simply
a dependent standpoint, it does appear that if you
ingest high levels of caffeine that is exceeding the
dosages that normally you could get away with
and get just as much mental-enhancing and
physical-enhancing benefits that you can cause
some disruption to the microvasculature. You can bias yourself towards
headaches, anxiety attacks, and you can become
actually quite irritable when you're not getting those
higher levels of caffeine.
So I do encourage
you to figure out not just what an appropriate
caffeine dosage would be for you but also
how much caffeine you might already be ingesting. The first tool I'd
like to talk about is one that I've
mentioned before on this podcast several times. And it's something that
if you haven't heard of will be very useful to you. And if you have heard
this tool before, I'm going to add some
additional features to the description
of this tool that should make this
worthwhile for you as well.
And that is to delay
your caffeine intake to 90 to 120 minutes after
waking up on most days. And I'll be very
clear as to days in which you might want
to ingest caffeine more closely to when you wake up. Why would you want to delay
your caffeine intake to 90 to 120 minutes after waking? The answer to that
is very simple. Many people wake
up in the morning. They drink caffeine within
10, 20, 30, sometimes within 2 minutes of waking. And they feel more
alert naturally. That makes sense because
of the effects of caffeine in blocking the
effects of adenosine that I talked about
earlier and its effects on other
neurotransmitter systems. But then what they find is
that, in the early afternoon, in particular, after lunch,
they experience a dramatic dip in their overall levels of
energy, the so-called afternoon crash.
And in most cases, the
way they respond to that is to ingest more
caffeine, which indeed can increase their
levels of mood and alertness. However, as we'll
soon talk about, there is a problem
with ingesting caffeine in the afternoon if it
falls within 8 or 10 or dare I even say 12
hours of going to sleep. And that is, the caffeine
ingested in the afternoon– for most everybody, let's say
for 95-plus percent of people– disrupts the
architecture and quality of their nighttime sleep. And I should say that
it doesn't necessarily impact their ability to fall
asleep and maybe even sleep through the night but that the
depth and quality of that sleep is disrupted by consuming
caffeine in the afternoon. A little bit later,
I'll talk about how you can offset some of
those negative effects if you absolutely require
caffeine in the afternoon. But there's a huge advantage
to restricting your caffeine intake to the early
part of your day but not consuming caffeine
within the first 90 to 120 minutes after waking. In fact, many people find that
if they delay their caffeine intake to 90 to 120
minutes after waking up that they feel more
alert in the morning, and they completely avoid
that afternoon crash.
Now that said, many
people, including myself, do need a short nap
or non-sleep deep rest or other form of relaxation
for 10 to 30 minutes in the afternoon. That is natural and healthy. I'm not referring
to the need for that when I refer to the
so-called afternoon crash. What I'm talking about
in the afternoon crash is a inability to recover
energy and focus and a need to consume more caffeine just to
make it through the afternoon. By delaying caffeine intake to
90 to 120 minutes after waking, there are a couple of things
that are accomplished. First of all, you offset
that afternoon crash. And this is an effect that
many people experience the very first time they
start delaying their caffeine intake to 90 to 120
minutes after waking. And the reason this works
so well is the following.
As I mentioned
earlier, adenosine is a molecule that builds up
the longer that we are awake. It is a molecule that
is reduced or cleared from our system by sleep. So when we emerge
from sleep regardless of how long we've slept,
our adenosine levels are lower than they
were when we went to sleep the previous night. If you slept well
enough and long enough, those adenosine levels
can be very, very low, but they are never
completely zero. When you wake up in
the morning, even if you're one of these people
that springs out of bed and is ready to attack the
day– and here I'm certainly not describing myself.
I'm not one of those people. I tend to wake fairly slowly. But if you're one of those
spring up and attack the day or you're one of
the people who moves more slowly into your
day, regardless, there's still some residual
adenosine in your system. And this is
particularly the case if you did not get enough
sleep or enough depth of sleep the night before. The correct ratio is a slow-wave
sleep and rapid eye movement sleep. And for those of you
interested in optimizing sleep, I'll just refer you to our
master your sleep episode of the Huberman Lab podcast,
the perfect your sleep episode of the Huberman Lab podcast. And we have a tool kit for sleep
all of which are available, zero cost, time-stamped, et
cetera at hubermanlab.com.
You wake up in the morning. And your adenosine levels are
low, but they're not zero. And if you didn't sleep that
well or deeply enough the night before, you're going to have
more adenosine in your system. You might think
the logical thing to do is therefore
to drink caffeine and to block the
adenosine that's there. But what happens
if you do that is there's an accumulation, a
sort of glut of adenosine that hangs around. And then in the afternoon, when
the effects of that caffeine start to wear off,
you will experience the so-called afternoon crash. As I mentioned
earlier, there is a way to clear out the adenosine
that's present when you wake up in the morning and to
clear it out essentially completely without just
blocking its receptors and letting it accumulate
or hang around.
And the way to do that
is to deliberately spike your cortisol. Now, many of you have heard of
cortisol, the so-called stress hormone, as a bad thing. And indeed, chronically elevated
cortisol is a bad thing. It depletes your immune system. It's bad for
psychosocial effects. It tends to make us feel
anxious and on and on. But cortisol itself is not bad. Cortisol is wonderful. Cortisol enhances the
efficiency of the immune system. It makes us alert and focused. It stimulates our metabolism. It does a huge number of
positive things, provided that it is released in
a circadian fashion.
That is, at the
appropriate times every 24 hours and that it tends
to peak very close to waking. In fact, one of the reasons
you wake up in the morning, assuming that you weren't
woken up by some noise or sleeping in an environment
that's too warm, et cetera, is that your cortisol
levels start to rise. And shortly after waking,
your cortisol levels will start to reach their peak. And when I refer to
a cortisol pulse, that's just biology
nerd speak for a rise and peak in cortisol. You want that cortisol pulse
to occur early in the day close to waking, and you want that
for a couple of reasons. First of all, if you don't
restrict that cortisol pulse to early in the
day, it will tend to bleed into the
later parts of the day.
And actually, a late
shifted cortisol peak is one of the
hallmark signatures of depression,
low-level depression, and serious depression. And it can start
to disrupt sleep and certainly can
disrupt mood metabolism and your immune system. So you want that cortisol
peak early in the day. How do you ensure
that that happens? Well, you wake up
in the morning. And whether or not you're
a bounce-out-of-bed type or you're more groggy, you kind
of wade slowly into the day type like I am, you wake up,
and you don't ingest caffeine.
Fine and, in fact,
beneficial to hydrate with water and electrolytes. Terrific. In fact, I would
say necessary to get bright light in your eyes
ideally from sunlight. I've talked about
this many, many times before on the podcast. If you wake up before
the sun comes out, then turn on bright
artificial lights. But then certainly once the sun
is out and even on cloudy days, in fact, especially on cloudy
days, get outside for anywhere from 5 to 20, maybe
even 30 minutes.
Do some work outside, take
your breakfast outside if you're a breakfast eater. Get something done outside even
if it's just to get outside and get bright
light in your eyes. Why? Well, because it's
been shown in studies on humans that getting
bright light in your eyes in the first hour after
waking or as soon as possible after waking increases the
peak of that cortisol pulse by 50%, 5-0. And that cortisol pulse, yes,
increases mood, yes, increases alertness, but it does one
other very important thing, which is that, through
an indirect pathway, it can clear out any
residual adenosine that might be present in your
system when you wake up in the morning. Again, this is going to be
especially important for those of you that are not
getting as much sleep or as much quality
sleep as you would like. It's going to be very important
for you to get that morning bright light ideally
from sunlight, get that cortisol peak going.
Other ways to increase
that cortisol peak would be to do some
physical activity. If you don't have time to do
a full workout, well then, getting some movement– 10 minutes of
skipping rope or even 5 minutes of skipping rope
or jumping jacks or walking if that's all you have time
for ideally while getting the sunlight in your eyes. But that's going to zero
out the adenosine present in your system. If, however, you were to
wake up and immediately drink caffeine– caffeine itself can
stimulate the release of cortisol a little bit
more than it would otherwise be present in your system. But by blocking those
adenosine receptors and because of the
indirect effects of caffeine on the
cortisol system, you actually are reducing
the clearance of adenosine that would otherwise occur.
So I realize that's a mouthful. Just to be very
clear, if you wake up and you ingest
caffeine right away, you're blocking the
adenosine receptor, but you're not clearing it out. You're also preventing cortisol
from having its normal increase and rise such that it can
directly clear out adenosine because cortisol can
clear out adenosine. And that's what you want. You want to be at
maximum alertness and focus in your morning
and throughout your day.
And by delaying your caffeine to
90 to 120 minutes after waking, you set up your system so that
you get that morning cortisol peak. Ideally, a peak that's
even greater because you're getting your bright
light viewing. And then when you ingest your
caffeine 90 to 120 minutes after waking, not only will
you be craving it just a little bit, but you will be
drinking that caffeine on an already existing backdrop
of increased alertness for two reasons. One is adenosine is zeroed
out, and your cortisol peak is higher. And so now when you
ingest caffeine, you can actually ingest
levels of caffeine that are a little
more reasonable that almost with certainty are
going to fall in this 1 to 3 milligrams per kilogram dosage
and will allow you to feel really alert and will
carry that alertness well into the afternoon hours without
the need to drink more caffeine and thereby will prevent
you from drinking caffeine and disrupting
your nighttime sleep.
And, of course, by getting
better nighttime sleep, you're going to zero out
your adenosine even more. So what I'm describing here
are essentially two tools. I'm telling you to get
morning sunlight and maybe some exercise in
conjunction with that even if it's brief exercise. But the main tool
of delaying caffeine 90 to 120 minutes after
waking has immediate effects, but it also sets in
motion a cascade or domino falls that lead to better
sleep and more wakefulness the next night and the next
day and so on and so forth. Now I realize there are some
people who just simply cannot or will not delay their caffeine
90 to 120 minutes after waking for whatever reason. First off, let me say
that, if you are somebody who likes to wake up and
do very intense exercise within the first 90
minutes after waking, well, in that case, it would
be appropriate to ingest your caffeine just prior
to doing that exercise. Not a problem. Not a problem. But you should expect that
the combination of drinking caffeine very shortly after
waking plus exercising very intensely shortly after
waking will increase the intensity of that early
afternoon and afternoon fatigue that you feel.
Now for some people,
that's a great thing. They can afford to take a nap
or do non-sleep deep rest, step away from work, and so forth. In that case, I
strongly encourage you to do whatever
it is that allows you to get regular exercise
because regular exercise is going to be very beneficial. In fact, we did
an entire episode called tool kit for fitness that
describes a couple of different but really one
main structure that allows you to get the
appropriate amount of resistance training and
cardiovascular training and flexibility training
throughout the week. I happen to follow that
program, and it works very well. And it does involve
some of those workouts to come very early in the
morning shortly after waking. And in those cases,
I do ingest caffeine just prior to those, so within
10, 20 minutes of waking. However, on other
days, I personally delay my caffeine intake
90 to 120 minutes, and I've done that
to great benefit. And most people, if not,
all people that try that, have reported the same. I should mention that some
people will find getting out to that 90 minutes
to be excruciatingly difficult because they're
so accustomed to ingesting caffeine close to waking up.
In that case, maybe just
push out your caffeine intake by about 15 minutes
each day until you hit that 90 to 120-minute mark. And that will make
it much easier. It might take you a
week or so to get there. But once you get
there, you'll find it to be quite easy to maintain. The other thing is that,
if you are somebody who insists on drinking caffeine
very shortly after waking, I would encourage you to drink
half of your caffeine then and then the other half of your
caffeine about an hour later. That also will help offset
some of the afternoon crash for reasons related to the
so-called kinetics of caffeine. Caffeine has a quarter
life of about 12 hours. That means that if you were
to ingest a cup of coffee at let's say 8:00 AM– and let's say 100
milligram coffee just for sake of simplicity,
that about 25% of that caffeine action– we wouldn't really say 25
milligrams, but about 25% of that caffeine
action will still be present at 8:00
PM that night, which is pretty remarkable.
So there's a long arc
of caffeine effects, and this is why it
can impede sleep if we take caffeine in the afternoon. But again, if you're
somebody who wakes up and you really need
caffeine right away and you refuse to do this
90 to 120-minute delay thing that I'm talking about,
well then, in that case, I would drink half of
your caffeine upon waking and then a little bit more or
the other half about an hour later.
And that will extend the
arc of that caffeine effects such that you don't need
it again in the afternoon because you won't experience
the afternoon crash. Because of the way
caffeine works, I should mention that,
if you ingest caffeine on an empty stomach, it will
have a more potent stimulant effect. That will also tend to increase
the level of jitteriness that caffeine can produce. Later, I'll talk about ways
to offset that jitteriness, but I'll just tell
you one tool now. Many people opt to take
100 milligrams of theanine, T-H-E-A-N-I-N-E, theanine, as
a way to offset some of that jitteriness. Theanine will reduce
the jitteriness of caffeine, which is
why many energy drink manufacturers and even
some coffee manufacturers are now putting theanine
in energy drinks and in ground coffee
because, no surprise, it allows people to consume
more of that beverage and thereby purchase more
of that beverage, which is what these vendors want
without feeling overly anxious and jittery. So you can take
pill form theanine if you want with your caffeine. I don't tend to do that.
Rather, I control the total
dosage of my caffeine. I do tend to consume
caffeine on an empty stomach because I do restrict
my caffeine intake to the early part of the day. And I generally eat my first
meal somewhere around 11:00 AM, and then I generally my last
meal some time around 8:00 PM or so. Those are averages. I would say plus
or minus an hour. And that's not because
I'm religiously following any kind of
time-restricted feeding. It's just that
tends to work best with my schedule
and my appetite. But again, that's
a general theme. There are days in which I
wake up and I'm very hungry, and I might ingest something,
small snack or something.
Or if I'm meeting
somebody for breakfast, sometimes I'll have breakfast. Sometimes I won't. And so on and so forth. The point is that
you can get away with drinking less caffeine to
get the stimulant effect if you do it on an empty stomach. And if you're somebody
who likes to exercise on an empty stomach– and I'm one of those people– well then, ingesting caffeine
just prior to exercise can be a fantastic tool. A little bit later,
we'll talk about some of the physical
performance-enhancing effects of caffeine. But I'll just briefly
jump to a point about that as we relate to
morning exercise. If you are somebody who
regularly ingests caffeine– and we can define
regularly by, if you've ingested caffeine every
day for the last two weeks, you're a regular
consumer of caffeine. Whereas if you're somebody
who only ingests caffeine somewhere between two and four
times per week, well then, you are not a regular
consumer of caffeine.
You're an intermittent
user of caffeine. Well, if you're somebody who's
a regular user of caffeine, the performance-enhancing
effects of caffeine are going to be most dramatic if you
take two or three days off from drinking caffeine,
which to my mind as a– I don't want to call
myself a caffeine addict but a regular caffeine user. That's a horrible notion to
me, it is an aversive notion, because I do like the
effects of caffeine so much. But if you really want
to see the maximum performance-enhancing
effects of caffeine, you will do either
one of two things.
You will either
abstain from caffeine for a few days or three days
prior to ingesting caffeine, or you will use caffeine
on an empty stomach. It's very clear that
caffeine on an empty stomach enhances both the mental
and physical enhancing effects of caffeine. And, of course, all of
that has to be stated on the backdrop of consideration
that you're very, very hungry, it can be make it
hard to concentrate and so on and so forth. So I'm not encouraging people to
starve themselves by any means. Certainly, don't do that. But if you want to maximize the
performance-enhancing effects of caffeine, you will consume
it on an empty stomach.
And then as a final point to
that, caffeine is a diuretic. It causes us to lose fluid
and, along with that fluid, to excrete sodium because
of the effects of caffeine on various processes
within the kidney. So one thing that works
very well to maintain mood and alertness longer given
a certain amount of caffeine intake and to avoid
the jitteriness and what can sometimes feel
like a crash or low blood sugar feeling or even blurry
vision is to make sure that you consume at least
an equal volume of water with your caffeine. And ideally, that
water would contain maybe a small pinch
of salt or some sort of electrolyte drink– or powder, rather. For me, I use element. Full disclosure, they are a
podcast affiliate and sponsor. But you don't need to do that. You could simply just have
a glass of water alongside your coffee or espresso or your
yerba maté and just put a small pinch of sea salt in that or
evem just playing table salt.
And that will help offset some
of the jitteriness of caffeine. A lot of people think that,
when they ingest caffeine, they get the jitteriness and
crash because their blood sugar is low. And while that can be the
case, oftentimes, it's simply because of the
excretion of sodium that's occurred when
they've ingested caffeine. So I encourage you
to hydrate well and to hydrate with
something that contains a little bit of sodium. Obviously, not so much
that increases hypertension or something of that sort
but a small amount of sodium or an electrolyte
drink like Element.
And there are other
electrolyte drinks out there that can accomplish
the same, of course. Just a couple of
quick notes about theanine because there are
a growing number of products out there that contain theanine. And there's certainly a growing
number of people out there who are using theanine for the
effect that I described before, which is to offset some of
the jitteriness associated with caffeine-containing
beverages or foods. And, of course, I
should mention that I've talked about the
effects of theanine on sleep at that sleep
tool kit that you can find as a free download.
You don't even have
to sign up for. Anything you just download
it from hubermanlab.com. Go to the menu, go
to a newsletter. You'll see the
tool kit for sleep. You'll see that the
so-called sleep stack that I use and recommend
includes magnesium 3 and 8, something called
apigenin and theanine, although that sleep
stack is designed to be taken 30 to 60
minutes prior to sleep. And I make the point
there, and I'll make it again here that
ingesting theanine prior to sleep is not a good
idea if you are somebody who tends to have very vivid
dreams, night terrors, or night walk– sleepwalking, excuse
me, et cetera. In that case, eliminate theanine
from the sleep stack.. . However, a number of
people are using theanine, and products are using
theanine to offset jitteriness from caffeine-containing
products during the daytime, daytime
consumption, that is. A couple of notes about
theanine– theanine is something that is
present in green tea, right? It's now been created
as a supplement. It's what's called a
nonprotein amino acid.
So while there are amino
acids and proteins, there are, of course, amino
acids and nonproteins. And theanine is one such
nonprotein amino acid. Theanine tends to stimulate
the so-called glutamate and glutamine pathway. It's actually very similar
to glutamate and glutamine, and it has a lot of effects
on a lot of different aspects of the nervous system. But the general
effect of theanine is to compete for the receptors
for certain neurotransmitters. And the neurotransmitters
I'm referring to are all excitatory
neurotransmitters, things like glutamate. And they govern a tremendous
amount of our daily thinking and action and
feeling, et cetera, because they're present
at so many connections between neurons in the brain. Theanine competes for the
receptors for glutamate and tends to reduce our
overall levels of alertness. So really, when people
take theanine along with caffeine,
what they're doing is they're really
taking a slight– I don't want to call it
depressant to the point where it misleads people and
makes people think that it will make you depressed.
The word is a little
bit misleading. But it tends to
reduce or blunt some of the more excitatory
pro-alertness actions of neurons in the brain. So when you take it
alongside caffeine, tends to, quote unquote,
"even things out a bit." I should mention that
the dosages of theanine that are effective
for offsetting the jitteriness of caffeine
is 200 to 400 milligrams, and the studies that
I was able to find showed that essentially up
to 900 milligrams per day can be safe. But that's a very high
dosage of theanine. In fact, so much so
that it might increase sleepiness to the point
where it wouldn't feel good. There are also some
positive effects of daytime consumption
of theanine that are independent of reducing
the jitteriness of caffeine. For instance, there's
a study demonstrating that 17 days of ingesting
theanine at these 200 to 400 milligram dosage at one
to three times per day can reduce depression
and anxiety.
There are also some good
data out there showing that theanine can have positive
effects on endothelial cells– so blood vessels,
capillaries, and so on– and increase some of the
function of blood vessels, allowing them to pass
more blood through them and give them a little bit
more elasticity, if you will. So theanine has certain
pro-sleep effects if it's taken prior to sleep. It can enhance the quality,
depth, and duration of sleep. Again, if you're a
sleepwalker or somebody who has extremely vivid dreams
from which you wake up in the middle of the
night, probably best to leave out theanine or
maybe reduce the dosage down to 100 milligrams.
And if that's still too much,
then eliminate it completely. But theanine can be terrific
for enhancing quality, depth, and duration of sleep. It can also reduce
the jitteriness associated with
caffeine-containing beverages and foods. And it has certain
antidepressant and pro-endothelial effects. That is, it can
offset depression. It can offset anxiety, although
those are minor effects, subtle effects.
And it has been shown to
improve endothelial cell. That is, vessel and capillary
function and structure in ways that can be beneficial
for both brain and body. Now one final point
about theanine that's worth paying
attention to is that the kinetics
of theanine are such that you don't need to take
theanine every time you ingest a caffeinated beverage. When we ingest caffeine,
the peak effects of caffeine occur about 30 minutes
after we drink it.
And there, I'm assuming
one takes it all at once. And this is a key point that
we'll come back to later rather than sipping your coffee
slowly over a couple of hours or an hour. If you drink all 200 or
300 milligrams of caffeine in your coffee or 600
milligrams of your coffee if you're getting one of
those commercial coffees and you take theanine
along with it, theanine will block
some of the jitteriness and anxiety-inducing
effects of caffeine that can occur for much
longer than the effects that caffeine lasts. So the peak in theanine occurs
about an hour after ingestion. I suppose if you want
to get really fancy and really dial in
the kinetics, you could ingest theanine
about half hour before you ingest your caffeine. But I think that's getting a
little bit excessive in terms of controlling your
microenvironment, if you will. I think it would be perfectly
fine to take a 100 to 200 milligram capsule of theanine
along with your coffee or tea or so forth and just realize
that if you drink more caffeine or you extend your caffeine
intake over several hours that you don't necessarily
have to take theanine repeated times throughout the day.
I'd like to take a
brief break and thank our sponsor, InsideTracker. InsideTracker is a
personalized nutrition platform that analyzes data
from your blood and DNA to help you better
understand your body and help you reach
your health goals. I've long been a believer in
getting regular blood work done for the simple reason that
many of the factors that impact your immediate and
long-term health can only be analyzed from
a quality blood test. The problem with a
lot of blood and DNA tests out there, however,
is that you get data back about metabolic factors,
lipids, and hormones, and so forth, but you don't
know what to do with those data. InsideTracker
solves that problem and makes it very easy
for you to understand what sorts of nutritional,
behavioral, maybe even supplementation-based
interventions you might want to
take on in order to adjust the numbers of those
metabolic factors, hormones, lipids, and other
things that impact your immediate and
long-term health to bring those numbers into the
ranges that are appropriate and indeed optimal for you.
If you'd like to
try InsideTracker, you can visit
insidetracker.com/huberman and get 20% off any of
InsideTracker's plans. That's
insidetracker.com/huberman to get 20% off. Let's talk for a moment
about when to avoid caffeine. And in the same stroke,
let's also talk about some of the myths around caffeine. For instance, one of the
major myths around caffeine is that it can
increase osteoporosis. It turns out that, while there
is a relationship, of course, between calcium
and osteoporosis– that is reductions
in bone density. And it is the case that
caffeine can extract calcium from certain tissues. The large scale studies that
are out there essentially prove that, if people are
ingesting enough calcium through their diet, which
most everybody is– although certainly, there
are some people that need to supplement calcium
or make it a point to consume more calcium-containing foods. But assuming that
you are getting adequate levels
of calcium, there is no direct relationship
between caffeine intake and osteoporosis, at least
not that I'm aware of. I know this was debated
for a number of years in the literature,
but the literature seems to have arrived
at a general consensus now that caffeine itself is not
going to create or exacerbate osteoporosis, provided people
are getting enough calcium through their diet.
That is, through foods, through
supplementation, or both. Some of the other
myths around caffeine are that, for instance, caffeine
will reduce testosterone levels or will reduce estrogen levels. Other myths out there
are in exact opposite to that, that caffeine will
increase testosterone levels, in particular, free
testosterone levels. There have been some large scale
studies addressing the hormone effects of caffeine. They are a little
bit difficult to do. I should just
mention that caveat. And the reason they
are difficult to do is because 90% of adults
are consuming caffeine. And therefore, you
can imagine it's very hard to find a control
group to compare the caffeine consumers to. In particular, a
control group that's well controlled for other things
like lifestyle, diet, exercise, et cetera. However, when one controls
as well as one can for all the various factors that
could impact hormones, what one discovers is that caffeine
intake, at least at the dosages we talked about earlier, 1
two 3 milligrams per kilogram of body weight or even
up to double that, that there are no consistent
increases or reductions in testosterone or
estrogen in men or women that can be directly attributed
to the caffeine intake.
And I say directly attributed
because in these association studies, one always
has to wonder, for instance, if because people
are ingesting more caffeine, they have more energy and
therefore exercising more. And exercise is
known to have effects on testosterone, estrogen,
and other hormones, whether or not the effects
of caffeine on those hormones is indirect and so
on and so forth. And this all just
underscores the challenges of doing studies on
humans in the wild in their natural habitat
of living as opposed to an acute study as it's
called to bring someone into the laboratory
and studying them just for those hours or moments. With all that said, there does
appear to be a relationship between caffeine intake and
so-called sex hormone binding globulin, which is a protein
present in the body of both men and women that binds to
the sex steroid hormones– testosterone and estrogen–
and prevents them from being in their
free or active form.
It has been shown that
ingestion of caffeine– even in the sorts of dosage
ranges that are considered safe and that we've been discussing–
can increase sex hormone binding globulin such
that it can slightly reduce overall levels
of free testosterone and free estradiol in women. Now those effects are relatively
minor, but they do exist. If any of you are interested
in reading further into the effects of
caffeine on hormones, I'll just refer you to
a couple of studies. We will link to this in
the show note caption. The title of the
study is "Consumption of caffeinated beverages and
serum concentrations of sex steroid hormones in US men." And within this study,
there is a reference to a equally sized
empowered study done on women, both of
which converged on the same conclusion, by
examining more than a thousand.
So in this case, 1,410 men or
more than a thousand women, that there are increases in
sex hormone binding globulin associated with increased
intake of coffee, in particular. But they were able to narrow
that down specifically to ingestion of caffeine. So it's not coffee per se that's
causing the increase in sex hormone binding globulin. It's actually caffeine itself. So again, the increases in
sex hormone binding globulin were not so significant
that, at least to my mind, they seem like a
concern, although I think that it is worth noting
that if you're going to consume caffeine that you probably
want to consume caffeine in a way that is in dosages and
with the sort of timing that will allow you to get away
with ingesting caffeine but not to excess, so to
derive the benefits of caffeine without for instance driving
up sex hormone binding globulin too far. Now why would that
be a good idea? Why would you want to make
sure that you have enough free testosterone and free estrogen? Well, some of that is
related to the acute effects of those hormones in terms
of well-being and libido and strength and mood, et
cetera, but some of those also relates to the longer
term effects of sex steroid hormones.
Many people don't
realize this, but the sex steroid hormones
operate on the receptors at the surface of cells
to have immediate effects. But they also can enter
cells and actually go into the nucleus of cells
where the DNA of those cells are contained and control gene
expression in those cells. So the sex steroid hormones,
testosterone and estrogen, are controlling a lot of
different cellular functions over long periods of time. So blunting their action
over long periods of time is probably not a great idea. But again, at the
dosages of caffeine that we're talking about
today, 1 to 3 milligrams per kilogram of body
weight, unlikely that the increases in sex
hormone binding globulin that one experiences from that
are going to be detrimental. And certainly, the
positive effects of caffeine that one experiences
in terms of mental performance and physical
performance and the fact that it increases energy
to do the sorts of things like exercise that we
know can profoundly improve hormone
profiles, twofold or threefold improvement
in hormone profiles.
In that case, it seems that
ingesting caffeine is overall a good thing, provided
it's not in excess. That also makes this
the appropriate time to mention one of the more
impressive effects of caffeine, which is on overall levels
of mood and mental health. There are several
studies on this, but the one that I'm
particularly fond of was published in 2019
in Psychiatry Research. And the title of the paper
is "Inverse association between caffeine intake
and depressive symptoms in US adults." And these are data from the
National Health and Nutrition Examination Survey. And the basic takeaway is
that, while, of course, there are a ton of
different factors that are going to
relate to whether or not people are depressed or
not, life circumstances, genetics, and so on, that– and here I'm quoting
from the study. "Caffeine's psychostimulant
properties– that just means
the ability to make us feel more alert
and positive– appeared to protect against
depressive symptoms." And, of course, they acknowledge
that additional studies are needed, but this is just one
of several studies pointing to the fact that people who
regularly ingest caffeine in the appropriate
dosages do seem to enjoy an antidepressive
effect overall.
I wouldn't want anyone
to consider caffeine a treatment for
severe depression or at least not
alone a treatment for severe depression. But provided the
anxiety-inducing effects of caffeine can be kept in
check through use of theanine or making sure that the dosage
and the timing of caffeine ingestion is correct,
then caffeine overall seems to be good for our
mood and prevent depression or at least keep
depression at bay when depression might otherwise
surface or be more severe. And, of course, there are the
don'ts surrounding caffeine intake as it relates to sleep. And to put it very
simply, sleep– that is getting
enough quality sleep each night– is the foundation. It is the bedrock of mental
health, physical health, and performance. Sleep and the power of sleep
far exceeds any nootropic you could ever take,
any prescription drug you could ever take, any
health-promoting tool for your immune system,
your metabolism, your mental function,
your physical function you could ever take.
Sleep is the bedrock. I know a lot of people
experience challenge with sleep. Nobody is perfect about sleep. That's important
to keep in mind. I think a good goal is
to get enough quality sleep of sufficient duration
80% of the nights of your life and then as much as possible
to make sure that the remaining 20% of nights you are
not getting enough sleep for good reasons as
opposed to hard reasons. Good reasons would
include raising children. That's important. After all, every species
desires to make more of itself and to preserve and extend
the well-being of its young, so child-rearing is a
perfectly legitimate reason to get a lack of sleep. But you really want to strive
to get quality sleep most nights of your life, which means that,
even if you're somebody who can, quote unquote,
"drink an espresso" and then fall right asleep,
that you avoid caffeine intake in the 12 hours prior to sleep.
I realize not everyone
will be able to do that. And in fact, I
sometimes violate that, so I tend to go to sleep
around 10:00 PM every night, sometimes 11:00,
occasionally 12:00 midnight, but usually around
10:00 PM every night. I confess that my last
ingestion of caffeine is not always 10:00
AM or prior to that, so sometimes I will
have caffeine up until 11:00 AM or maybe noon. And very, very rarely, I'll have
an afternoon coffee or espresso or noncalorie-containing
soda or tea or something that's of that sort. But I really tried to
restrict my caffeine intake to the early part of my day
that is before noon, given that I go to sleep around
10:00 PM each night. And I strongly encourage
everyone out there to try and limit their
afternoon caffeine intake. This is something that Dr.
Matt Walker, who's an expert sleep researcher out of
University of California Berkeley Psychology and
neuroscience department there, author of the incredible
book Why We sleep.
He's been on this podcast,
many other podcasts, talking about the
importance of sleep. He will remind us, and
I'll remind you now that the quarter life
of caffeine is 12 hours. I mentioned this earlier, but
I'm going to repeat it again. And that means that, if you
ingest caffeine at noon, 25% of its effects
more or less, OK? I'm using a broad stroke here
to talk about quarter life. 25% of that is still going
to be bioactive at midnight that night, which will disrupt
the early phase of your night, the amount of slow-wave
sleep, which then in turn will disrupt the amount of rapid
eye movement sleep, which will disrupt your
emotional processing during the following day
and so on and so forth.
None of this is
to say that if you have the occasional cup of
coffee in the afternoon, that it's going to
completely demolish your sleep/wake cycle forever. But I really encourage people
to avoid drinking caffeine in the 12 hours prior to sleep. And if you can't do that, within
the 10 hours prior to sleep. And if you can't do that, within
the 8 hours prior to sleep. So really try and
limit your caffeine intake in the 8
to 12 hours prior to going to sleep at night. And, of course, slow-wave
sleep, aka deep sleep, is the sleep that's associated
with somewhat mundane dreams, which makes it sound like it
might not be that important.
But it's also the sleep that's
associated with growth hormone release, which is important
for protein synthesis, repair of all bodily
tissues and metabolism. And slow-wave sleep
is also critically attached to your
immune system's ability to clear out bacteria and
viruses that might otherwise infect your tissues. Now I'd like to talk about
caffeine and performance. And that includes both
mental performance and physical performance. Now I'd like to
talk about caffeine and its positive
effects on performance when used correctly. And here we are referring
to both mental performance and physical performance. The exploration of caffeine
as a pro-performance tool has been explored since
the 1930s, at least that's some of the earliest
documented literature on this. Although I have
to imagine, given that people have been
using caffeine for much longer than that, that long
ago somebody realized that, by ingesting a certain
plant, that they felt much more
alertness and were able to hunt and gather or do
any number of different things better and, as a
consequence, decide to consume more of that plant.
Now these days, we
consume a lot of caffeine in the form of coffee
and tea mainly, and some people consume it in
the form of caffeine tablets or energy drinks, et cetera. Across the board, one
finds that caffeine intake at a level of 1 to 3 milligrams
per kilogram of body weight improves reaction time. That is, it reduces
the amount of time to take a physical action or
to answer a question correctly with a verbal response. It can also improve
coordination. It can also improve
memory, although I do want to mention that, whereas
most studies of the effects of caffeine on improving
mental and physical performance involve taking caffeine at 1
to 3 milligrams per kilogram of body weight before the
mental task or physical task, there is also a pro-performance
effect of caffeine on memory if one takes caffeine after
learning certain material or I should say being
exposed to certain material.
We'll come back to
that in a few minutes. If one examines reaction
time, mood, alertness, focus, and memory or the
ability to call up information from memory, or
physical dexterity, power output, endurance, and
overall feelings of well-being during exercise and
exertion, caffeine has been shown in numerous
studies in both men and women to improve all of those
metrics significantly. So this is all just
to say that caffeine is an incredible
performance-enhancing tool. Now, what's not obvious from
the statement that caffeine is a performance-enhancing
tool across the board and in men and women and
in different contexts is that the way in
which caffeine is taken is very important. Because 90% or more of
adults consume caffeine, finding controls for studies of
caffeine is really challenging. That is, finding people
who don't ingest caffeine regularly is a very challenging
task for the researcher.
And as a consequence,
many of the studies of caffeine on
human beings involve depriving regular
caffeine users of caffeine and then examining the
effects of caffeine given after a period of, say,
5 to 15 days of abstinence in a person that is essentially
experiencing mild withdrawal symptoms because they haven't
had the caffeine that they were used to getting. So this is an important point. And it's a point that
likely exacerbates the observed pro-performance
effects of caffeine. Now all of that isn't
necessarily a problem, provided you keep it in mind. And it actually points
to a way in which even if you're a
regular caffeine user, you can extract more of
the benefits of caffeine. The simplest way to
do this, for instance, is to look back to what we
talked about earlier in terms of the need to have most of your
cortisol increase restricted to the hour or hours just
after waking in terms of mood and alertness and performance.
One of the ways to increase
the peak of that cortisol early in the day is to
consume caffeine shortly after that peak occurs. And this was really
nicely demonstrated in a study entitled
caffeine stimulation of cortisol secretion across
the waking hours in relation to caffeine intake levels. We will provide a
link to this study. It's a somewhat
complicated study because they looked at a bunch
of different times of day for caffeine intake. And I should mention,
in this study, they use this 300 milligrams per
day or 600 milligrams per day. So that's quite high, although
for people of sufficient body weight and who are accustomed
to taking caffeine, it's certainly not
going to be in excess of what a lot of people
out there are taking. But basically, what they
observed was the following.
Cortisol responses to
caffeine are reduced but not eliminated in people who consume
caffeine on a daily basis. What this means is
that, if you wake up– as I recommended
earlier, you avoid drinking caffeine for the first
90 to 120 minutes after waking, but you do get some sunlight or
other bright light in your eyes in that time, maybe
even get some exercise in that time, which
would be even better– and then you ingest caffeine,
you will get a further increase in cortisol, which,
provided it's restricted to the early part of the day,
is a good thing overall for mood and alertness. So this is a simple
performance-enhancing tool, which is to stack
caffeine on the tail of that early cortisol peak. I should also mention,
however, that, in this study, they had people do a five-day
caffeine abstinence prior to being tested with 300
milligrams or 600 milligrams of caffeine. So the simple tool to extract
from this and other studies like it is that, if
you want to experience the maximum alertness-promoting
effects of caffeine when you ingest it
early in the day, you would abstain from
caffeine for five days and then ingest caffeine 90
to 120 minutes after waking.
I would still hope that you
were doing all the other things that I described– morning
sunlight, exercise, et cetera– correctly. But regardless, it's very clear
that a five-day abstinence from caffeine however
painful that might be will increase the
performance-enhancing effects of caffeine when you take
caffeine on that sixth day. Now, I'm sure many of you out
there are saying, why would I ever want to abstain
from caffeine for five days in order to just get this
six-day performance-enhancing effect? Well, there are a couple
of reasons for doing that. Perhaps you're planning to
travel to a new time zone, and you want to use
caffeine as a stimulant to stay up during the
day in the new time zone. That's a somewhat unusual case. Others of you
might be interested in the pro-physical performance
effects of caffeine. We'll talk more about
these in a little bit. But you want to get
the maximum strength increase or the maximum
endurance increase from ingesting, in this
case, 300 to 600 milligrams of caffeine. Well, in that case, abstaining
from caffeine for five days will greatly exacerbate
the pro-performance effects of caffeine when you take
it on that sixth day, although admittedly,
those five days are likely to be pretty painful if
you're a regular caffeine user.
Another variation
on this, however, might be to have the
amount of caffeine that you ingest on a daily
basis and then go back to your regular level of
caffeine intake on that day in which you need the
caffeine to really boost your mood, energy,
and performance. Another reason why you might
want to abstain from caffeine or reduce your caffeine
intake for a period of time and then go back to your
regular caffeine intake is simply to identify how
much of an effect caffeine is really having on your overall
level of daily functioning and mood. This was something
that was actually covered in beautiful detail
in a book by Michael Pollan all about caffeine.
It's available on Audible. I really enjoyed that book. It describes his experience
with the decision to completely
abstain from caffeine for a period of months, although
I confess that after hearing that book, what it
basically made me want to do is never quit drinking
caffeine because it sounded as if, at least my
interpretation was, that even after several weeks
or months of abstaining from caffeine, that
he still fantasized about the effects of caffeine. But he did mention that, when
returning to ingesting caffeine after a period of
long abstinence, that it had almost a– let's not call it a
psychedelic property, but it had such
obvious effects on mood and alertness and
feelings of well-being that it really highlighted
for him the extent to which caffeine normally was
allowing him to just function what he thought was normally.
So in other words,
many of us don't even really know what our
normal basal level of cognitive and
physical functioning is because we're
ingesting caffeine on such a regular basis. I confess that, as much
as I enjoyed that book and as intriguing as his
description of caffeine abstinence and then the
return to caffeine was, I don't intend to ever
find out personally. Now a very good
reason why you might want to abstain from caffeine
for a deliberate period of time and then return
to caffeine intake is for its physical
performance-enhancing effects. And here we can look to a
really interesting study. The title of which
is "Time course of tolerance to the performance
effects of caffeine." And what I like about this
study is that, while yes, it does say that
abstaining from caffeine and then returning
to caffeine intake can enhance physical performance
in a very specific way, it also says that, if you
take caffeine regularly, you can still see the physical
performance-enhancing effects of caffeine.
Although they are not quite
as robust as they would be had you abstained from caffeine. The design of the study
is pretty straightforward. They had people either
ingest 3 milligrams per kilogram of caffeine
for 20 consecutive days. Many people are already
doing that, I realize, but they had people
do that or ensure that they were doing that. Or others ingested a
placebo for 20 days, so they abstained from
caffeine without realizing it. Then after that 20 days of
either ingesting caffeine or a placebo, their
peak performance was measured in terms
of aerobic output. But prior to that measurement,
they had caffeine, OK? So it's 20 days of caffeine
and then a 21st day of caffeine and then the physical
task on that 21st day.
Or it's 20 days of
abstinence from caffeine. And then on day 21,
you get caffeine, and you get the
same physical test. And what they discovered was
that the ingestion of caffeine increased peak performance
in this aerobic output dramatically if people had
abstained from caffeine. But for people that had consumed
caffeine all the way through up until that day, it still was
effective to ingest caffeine on day 21 but not as effective
as it would have been had they abstained. And in fact, the
magnitude of what they call ergogenic
effect, which is the pro-performance-enhancing
effect of caffeine, was higher on the first
day than in subsequent days when they allowed people to
continue caffeine intake. So the takeaway from this study
is really straightforward. If you want to get the maximum
physical performance-enhancing effects of caffeine, you abstain
from caffeine for 20 days.
Then on day 21,
when you're going to do the physical
thing, the task, you ingest caffeine about
30 minutes to an hour before you do that
physical challenge. Now 20 days of
abstinence is going to be rough for a lot of people. I certainly don't want to
sign up for this study. In which case, you might want
to do five days of abstinence as we talked about before.
And then on day six is the day
that you ingest caffeine and do the physical task. There are even some
studies showing that you can abstain from
caffeine for just two days, for just 48 hours. And, in particular, if you are
a regular user of caffeine, this allows you
to, on day three, ingest caffeine at the dose
that's appropriate for you and do the physical, or I should
mention mental performance task and perform significantly
better than those that have been taking caffeine
throughout the entire period leading up to the challenge.
So you don't necessarily
need to abstain for 20 days in order to get the
pro-performance effects of caffeine on day 21. You could do five days of
abstinence prior or even two days of abstinence prior. Or if that's intolerable
to you as it is in my mind, to me, to just reduce your
caffeine intake slightly or even perhaps have it
if you can tolerate that in the week or two weeks
or maybe even three weeks preceding some
physical or mental challenge.
Now again, this sort of
implies that you're going up against a marathon,
or you're going up against a series of long
tests, maybe standardized tests in one day. There, I just really
want to point out that there is an abundant
literature showing that people perform best on mental tests
if they are in the state that they were when they
studied for that material. Now in college, I knew
a number of people who took this to the extreme,
thinking that if they were to study under the
effects of alcohol, that they would be best
off consuming alcohol prior to taking exams.
And it turns out
to not be the case. Here we're talking,
in particular, about psychostimulant effects of
caffeine and other compounds. So don't think
that you can drink or be under the influence
of THC and then take– when you study and then take an
exam under the same influence and do just as well as you would
had you not ingested anything. Please don't let
that be the takeaway. However, do let
it be the takeaway that caffeine's
effects are made more potent by a brief to not so
brief period of abstinence prior to taking a
dosage of caffeine. And then the final
point to make is that, if you are somebody who
is not accustomed to drinking caffeine, meaning you're
hypersensitive to caffeine or you don't regularly
ingest caffeine, please do not ingest
caffeine on the day of any important mental
or physical challenge or performance, because
what you will find is that because you are
not caffeine-adapted, you will experience changes
in your thermal regulation, in your levels of
anxiety and jitteriness, and your levels of
focus that could be very detrimental to mental
or physical performance.
So you don't want to throw
yourself in the deep end by ingesting caffeine if
you're not used to it. And I should mention
that for people that are not accustomed
to ingesting caffeine or are very sensitive
to caffeine. Even 25 to 50 milligrams
of caffeine in the amount that's found in, for
instance, a piece of certain types of chocolate
can actually cause anxiety. So be careful there. Here, I'm referring only to
people that are accustomed with caffeine intake. So what I recommend is to
explore the ergogenic effects of caffeine during your training
and then to make a decision about what you can
reasonably and reliably do in terms of abstinence and
then pulse with caffeine on the day of the challenge. I get a lot of questions
as to whether or not caffeine has different
effects on the nervous system and on performance in
particular, depending on phases of the menstrual cycle.
So I explored that in my
research for this episode, and I found two
studies both of which we will reference in
the show note captions. The first one is entitled
"Caffeine consumption and menstrual function." So it's actually the
relationship between caffeine and menstrual function. We will do an entire episode
about the menstrual cycle and menstrual function. But the other one as it
relates to performance was published in 2020 in the
European Journal of Nutrition, which is "Ergogenic
effects of caffeine on peak aerobic cycling power
during the menstrual cycle." And the basic takeaway
of this study is– frankly, a very nice study,
showed that quote, "Caffeine increased peak aerobic cycling
power in the early follicular, preovulatory, and midluteal
phases of the menstrual cycle." Thus, the ingestion–
and again, here they use 3 milligrams of caffeine
per kilogram of body mass might be considered an
ergogenic aid for women who are in the menstrual
cycle during all three phases of their cycle.
So keep that in mind, women– for those of you that are
regular users of caffeine or you're using caffeine to
enhance physical performance, there does not seem to be any
menstrual cycle phase-dependent effects of caffeine
on performance. That is, caffeine seems
to always increase physical performance
regardless of the phase of the menstrual cycle
you might happen to be in. I'd like to touch on a little
bit more of the use of caffeine for enhancing
mental performance. Yes, it is the case that
ingesting 1 to 3 milligrams of caffeine per kilogram of
body weight in the 30 minutes or so prior to
doing a memory task or sitting down to
doing some studying or learning of any kind,
physical or mental performance, of any kind is beneficial
for all the reasons we talked about before, relate to dopamine
and acetylcholine, et cetera. But it turns out that
it is also the case that spiking one's adrenaline
and other so-called catecholamines– so this would
be dopamine, norepinephrine, and epinephrine– after
a bout of learning can greatly enhance
memory for the information that one was trying to learn.
That's right. Spiking your adrenaline
after learning can greatly increase
memory for the material you're trying to learn. In fact, this is a practice that
dates back centuries and was written about in a beautiful
Annual Review of Neuroscience on the biology of memory by
James McGaugh, where he talks about medieval
practices of children being taught information and
then being thrown literally into cold water to stimulate
the release of adrenaline and that increase in adrenaline. While the mechanism wasn't
completely understood, it was understood that
that sort of shock to the system from
the cold water led to better memory and
retention of the information that these children
had been exposed to.
And it turns out
the exact same thing is true for adults
in the laboratory or kids in the laboratory. And here I'm not
suggesting throwing anyone into cold water. If you want to get
into cold water, there's a reason we
call it deliberate cold exposure on the
podcast is that it should be deliberate and
controlled by you, not by somebody else. And if it's controlled
by somebody else, that might be military
screening or something. But here we're talking about
deliberately increasing your levels of adrenaline and
other catecholamines, dopamine, norepinephrine, et cetera. You can do that certainly
by deliberate cold exposure with a cold shower or
getting in up to your neck in cold water of any kind.
But the other way to do that
is to spike your adrenaline by ingesting 1 to 3 milligrams
per kilogram of caffeine after sitting down to try and
learn some material I confess that, more often than not, I
use caffeine in the same way that most people
use it, which is OK. I'm going to sit down. I'm going to research
information for a podcast or assemble some information
for a paper or grant, and I want to focus. So I will drink a cup of
coffee at the beginning of that and maybe even throughout
that or a couple of yerba maté at the beginning
or throughout that. Or I'll sip on one or both
throughout trying to learn. And that works
quite well in terms of maintaining focus and
alertness and retention of information, but
it is indeed the case. That is, the research
supports the fact. And I've experienced
the fact that, if I abstain from caffeine while
I'm trying to learn something– but then I drink caffeine
immediately after.
Somewhat surprisingly to me
but certainly in a way that's consistent with the
research literature, memory for the information that I was
focused on prior to ingesting that caffeine is much greater. And here I'm talking about
as a personal anecdote, but this is actually what the
data point to both in animals and in humans. And if you think about
it, it makes perfect sense because the way that the
memory systems of the brain are organized is that we go
through life experiencing things. We encounter surprises
both good and bad. We go through the motions of
things both typical, mundane, exciting, and novel,
and not novel. And then every once
in a while, something will happen that will
spike our catecholamines. Dopamine, typically if
it's a positive surprise. Adrenaline, which
can be associated with both positive
surprise or positive events and negative events
or surprises. And without fail, increases
in the catecholamines tend to lock in
memories for things that preceded the increase
in those catecholamines. Again, the catecholamines
being dopamine, epinephrine, and norepinephrine, sometimes
all three in combination, sometimes just two of those,
sometimes just one of those, depending on the experience.
So it makes perfect
sense that using caffeine at the end of a
learning bout would enhance our memory
for the information that we are trying to learn. So if you decide that you
want to try and extract this performance-enhancing
effect of caffeine, what I recommend would be to try and
abstain from caffeine for a day or two prior. But if you can't,
you just continue with your normal
caffeine intake. But then when you sit down
to study or learn something to not ingest any caffeine as
you do that but then afterward to ingest caffeine. Now in theory, you could
probably further enhance the memory encoding
effects of adrenaline and the other catecholamines
by drinking caffeine and then taking a cold shower or
doing deliberate cold exposure if you really wanted to
or had the ability to or doing some sort of
intense form of exercise.
And we'll talk in
a moment about how caffeine, exercise, and the
adrenaline system interact. But as a brief but
relevant to side, brief bouts of intense exercise
ranging from 10 to 50 minutes or so have been shown to
improve memory for information that one was trying to learn
prior to the intense exercise. This is work from Dr.
Wendy Suzuki's lab at NYU as well as other
laboratories, some of the work that's being done at Stanford
in the Mind, Body Laboratories. And our laboratory points in
the direction of these kinds of effects as well. They all come back to the
same general neurochemical theme, which is that,
when we experience an increase in these
catecholamines that include adrenaline, dopamine,
and norepinephrine, the memory systems of the
brain flip on in a way that try to capture the information
and the perceptions and the experiences that we
were exposed to just prior to the increase in
catecholamines and caffeine but also exercise
and also cold water. And, of course, any of those
alone or in combination all increase the levels
of catecholamines, so it makes perfect
logical mechanistic sense as to why this would work.
And in fact, it does work. If you want to remember
specific information, you might consider using
caffeine as you move through and absorb and are exposed
to that information. But you might also
consider using caffeine after being exposed
to that information because studies in
animals and humans show that that is a potent way
to increase memory for what you are just exposed to. I should mention that
what I just described also pushes back on something that
I know a number of people perhaps have heard about
and maybe even use, which is this notion of the nappuccino.
I remember hearing about
this a few years back. It was sort of
trend, if you will. The trend involved
drinking a cup of coffee or a double espresso and then
going down for a nap typically in the afternoon
and then waking up. And the idea was that the
caffeine would hit your system right at the time that
you awake from the nap and that you would be better
able to focus and exercise. There are a couple of things
about that practice that I don't like. First of all, it
implies, in most cases, that you're napping
and ingesting caffeine in the afternoon, which
I realize for many students and for people that are
comfortable staying up until the wee hours of the
night and then waking up late the next day might be
compatible with their schedule.
But again, because of the
sleep-diminishing effects of caffeine– and we talked about earlier. I'm not crazy about
the idea of people ingesting caffeine
in the late afternoon in order to perform better
in the late afternoon. Far better would be to
restrict caffeine intake to the early part of the day
as we talked about earlier. The other reason
is that the data on things like
non-sleep deep rest and naps in the afternoon–
and again, the rule here is that you don't have to nap. But if you want
to nap, it's been shown that naps of
90 minutes or less or non-sleep deep rest
protocols– and you can find those– for instance,
there's one with me speaking. You just put NSDR
Huberman into YouTube. You can hear that. It's completely zero cost. There are other NSDR
scripts out there now, of course, if you prefer
those, that those can all lead to increases in one
of the catecholamines at least, which is dopamine. That's been shown in a really
nice neurotransmitter labeling study, not from my laboratory,
but from another laboratory, but also can improve mood,
focus, and alertness on its own without the need to
ingest caffeine prior to going into those states.
And in fact, ingesting
caffeine prior to a nap or ingesting caffeine
prior to NSDR is most certainly going to
reduce the effectiveness of that nap and
NSDR in restoring natural levels of
alertness and focus that would lead to the
performance-enhancing effect. So I'm not such a fan of
the so-called nappuccino, although if any of you
out there have derived great benefit from
it, definitely let me know your protocol
and what you've experienced. Put it in the comment
section if you would. I'd appreciate that. There's another very important
and potent use of caffeine for enhancing performance.
And this relates not just to
the dopamine and epinephrine and the arousal-inducing
effects of caffeine. And it doesn't even just relate
to the effect of caffeine on enhancing frontal
lobe function. It does include all
that, but it also includes those reinforcing
effects of caffeine that we talked about at the
beginning of the episode. And the best way to illustrate
these performance-enhancing effects of caffeine
that stem directly from its association
with reinforcement is to highlight a study. And the title of the study
is "Blood dopamine level enhanced by caffeine in men
after treadmill running." And as the title suggests,
this was carried out in men, but there's no reason to think
that the same results wouldn't also be present in women. There are some sex-dependent
effects of caffeine. I'll touch on just
briefly at the end.
But those are largely
present in kids. That is, adolescents and
teens as opposed to adults. So this study is
really interesting. What they had people do was
run on a treadmill and either ingest caffeine– again, 3
milligrams per kilogram of body weight– or to not ingest caffeine. And then they looked
at levels of dopamine and other neurotransmitters
and hormones, such as prolactin and cortisol. And the basic takeaway
is, as the title suggests, that exercise, while on its
own, can increase cortisol in healthy ways, provided it's
not too intense and too long. A little note here, if you
have trouble recovering from exercise or
you want to continue to derive the benefits from
exercise, in general, best not to do high-intensity exercise
for longer than 75 minutes.
Or 90 minutes probably
being the outer threshold. I realized that there are
some genetic freaks out there or people that are
chemically assisted that can recover from very
intense long bouts of exercise. But most people don't do
well through long bouts of intense exercise
on a regular basis. And limiting their
intense exercise to 60 minutes or less– that doesn't include
the warm-up– is going to be beneficial. See the episode on
tool kit for fitness if you'd like details on that. Exercise is known to increase
levels of dopamine, cortisol, and other catecholamines and
neurotransmitters very potently and things like
testosterone and estrogen in ways that we know
are beneficial to us and, of course, have all
these positive effects on the musculoskeletal system
and cardiovascular effects.
But unbeknownst to most
people, ingesting 3 milligrams per kilogram of caffeine
prior to exercise further increases the dopamine release
associated with exercise specifically. And this has two
important effects. First of all, that
increase in dopamine is great because it provides
a long-lasting increase in focus alertness
and motivation, not just during the exercise,
but also after the exercise. And second, it– that
is, caffeine and dopamine in combination–
act as a reinforcer to make the experience of
exercise and the period immediate after exercise
more pleasant and, in fact, reinforcing. So in other words, one
way to enjoy exercise more and to enjoy the activities
that follow exercise more and to experience a genuine
increase in dopamine that's beneficial for
mood and alertness is to ingest caffeine
prior to exercise. Now this is important because
a number of people out there are exercising, love
exercise, love eating great, love doing all the
things that are beneficial for their health,
but a number of people out there really don't like to exercise.
And that serves as a serious
block for their willingness and their consistency
to exercise. Ingesting caffeine gives
us energy to exercise. It increases the release of
neurochemicals and hormones that are good for
us during exercise. But as I'm highlighting
here, it also increases the
reinforcement pathways associated with exercise. That is, it creates
a positive feeling about the general theme
of engaging in exercise, and it creates a general
positive experience of the things that
follow exercise. So I think this, if nothing
else is a call for or support for the idea, that
ingesting caffeine as a performance-enhancing
tool makes perfect sense. But for those out there
that don't enjoy exercise, in particular, certain
forms of exercise, ingesting caffeine can
change your relationship to that exercise. In other words, make it more
positive, much in the same way that ingesting caffeine
alongside a certain taste that would otherwise be neutral
or maybe even negative can actually make the taste of
that particular drink or food positive. So again, this brings us back
to the reinforcing properties of caffeine that
are subconscious.
It's not just about the
enhanced performance in the test or the enhanced performance
on the treadmill or with the weights in the gym. It's enhanced feelings
of mood and well-being that are genuine because
of the effect of caffeine on certain neurotransmitter
and hormone systems, but it also is creating
an overall milieu of reinforcing all
of the things that led in to occur during
and occur after exercise. I do want to point out something
that's very important as it relates to combining
things like caffeine and exercise in order
to increase dopamine. This is something that
came up in the episode that I did on dopamine,
motivation, and drive, which turns out to be one of
our most popular episodes.
Again, you can find that at
hubermanlab.com and links to all formats with
time stamps, et cetera. This also came up in
the episode on ADHD because of the relationship
between ADHD and dopamine. And that's this notion
of dopamine stacking. In the episode on dopamine,
motivation, and drive, I pointed out that, while there
are a near-infinite number of things that can
increase dopamine release, most notably positive surprise
or positive anticipation or experiencing a win.
Certainly, there are compounds,
both drugs of abuse, food, sex, and certain supplements
that can increase dopamine to varying levels and
to varying degrees, both healthy and unhealthy. That's all contained in
that episode on dopamine, motivation, and drive. But what I pointed
out is that, if you are somebody who tends
to experience difficulty with motivation– that
so-called dopamine stacking as I called
it might be something that you want to avoid. What's dopamine stacking? Dopamine stacking
would be combining a highly caffeinated energy
drink that also includes the amino acid tyrosine, which
is a precursor to dopamine, plus loud music plus getting
yourself really ramped up then an intense workout.
All of that can be great if you
do it every once in a while. But what you will quickly find
is that the extent to which your dopamine
peaks also dictates the extent to which
your dopamine will drop after that peak. And when I say drop, I
mean drop below baseline. So a lot of people find that,
if they stack a lot of things to peak their dopamine,
then they experience a low, and it does take some time for
them to return to baseline. And I highly recommend
not engaging in activities or consuming compounds that
are in attempt to accelerate that return to baseline
because all it will do is drive that baseline
lower and lower. So this requires
being able to tolerate a drop in dopamine baseline for
a period of time, et cetera. Now the reason I'm
bringing this up now in the context of
this caffeine episode is I just described a study
in which using caffeine prior to exercise increases
dopamine after exercise. And so you might be
saying, especially if you heard that earlier
episode, wait, isn't that dopamine stacking? Aren't you encouraging
me to stack my dopamine? Well, in some sense, yes.
But keep in mind,
I'm not suggesting that you do this every
time you exercise. So just as in that
earlier episode, I emphasized the fact
that, while stacking multiple stimuli– caffeine or energy drinks
and music and et cetera– for exercise or for mental
work or for any experience for that matter is OK to do
every once in a while for most people, you don't want to
get in the habit of doing it consistently every
time you exercise or every time you go
out, for instance. And so you really
want to be cautious. That is, you want to
protect your both baseline levels of dopamine and your
peak levels of dopamine. That said, for people
that want to experience an increase in mood,
alertness, and performance, or who want to
condition themselves– because that's
really what it is. It's conditioning yourself
by the reinforcing effects of dopamine to increase
your liking or maybe even your loving of exercise. Occasionally, using
caffeine or frequently using caffeine prior to exercise
is fine but be very careful. And by being very
careful, what I mean is pay attention to how you
feel in the hours and days after that dopamine
increase wears off.
So for instance, if you ingest
caffeine and then exercise very intensely and you're
feeling great afterwards but then eight hours
later or the next day, you're feeling a
little bit low, I suggest you don't go back and
do the exact same thing right away. I would give yourself
a little bit of time to let that baseline of
dopamine return to normal. So again, stacking
different things, chemical and behavioral, in
order to increase dopamine can be done in a safe way
that's beneficial to you, depending on your goals. But be careful about not
stacking too many stimuli for dopamine too often. That's the key. Early in the
episode, I mentioned one possible
caffeine-consuming schedule that works very well that
doesn't fortunately subject you to long 20-day bouts or 5-day or
even 2-day bouts of abstinence.
And that's the every other
day schedule of caffeine. If you look at the
half-life of caffeine and you look at its effects
on the dopamine system and its
performance-enhancing effects and how a period of abstinence
can, in fact, increase the performance-enhancing
effects of caffeine– but also take into
consideration that caffeine can be habit-forming, and we
can develop a sort of tolerance to caffeine. Well then, what emerges
from all of that is that being a person
who consumes caffeine every other day
can actually help you maximize most of the
positive effects of caffeine without subjecting you to the
kind of misery that occurs if you're accustomed
to consuming caffeine every single day and
then suddenly go into a 2 or 5 or 20-day abstinence.
So I myself have never tried
an every other day caffeine approach, although
I'm considering doing it based on the
literature that I've read. And I'm considering doing it
in a very specific way, which would be to only consume
caffeine on the days in which I resistance train. And since I tend to do that
about three or four days per week organized in a way
that's every other day– again, if you want to see the exercise
schedule that I follow, including cardiovascular
exercise and weight training and all the reasons
and rationale for what I do and how it maps on to the
scientific literature, relate to health span and
lifespan, vitality, et cetera, you can find that
at hubermanlab.com. And we had a tool
kit for fitness that ought to be posted to
our website before long.
The every-other-day schedule
of caffeine intake, to me, seems like the most
rational one if one wants to maximize on the
performance-enhancing effects of caffeine without suffering
the effects of caffeine withdrawal that are
associated with being a regular consumer of
caffeine and then stopping caffeine intake, such as
headache and irritability and so forth. Not I nor anyone
in my life wants me to experience
those effects, and I'm sure you don't
want to experience those effects for you either. So if you're
somebody that decides to try the every
other day protocol or you are somebody who's
already doing that protocol, please let me know what your
experiences with that are. At least by my read of
the literature on caffeine and it's
performance-enhancing effects but also the effects of caffeine
on neurotransmitter and hormone systems, the every-other-day
caffeine schedule does seem to be the most
rational and scientifically grounded one in order to
maximize on all those effects. In addition to so-called
performance-enhancing effects of caffeine, there are also
the well studied and now fairly well mechanistically understood
pro-health effects of caffeine. Now, here when I talk about
pro-health effects of caffeine, I want to be very clear that,
if your schedule of caffeine intake– that is, your timing
of caffeine intake or anything else
for that matter– offsets getting regular
high quality sleep of sufficient duration,
well, then you are undermining the pro-health
effects of that thing.
This is true for exercise. This is true for caffeine. This is true for
supplementation. This is true for
prescription drugs. Again, you don't want to
be neurotically attached to the idea that you have to
get perfect sleep every night because that's simply not
true but is absolutely the case that anything, whether
or not it's good for you or bad for you in the short
term, that disrupts your sleep because of the timing in which
you're doing that thing is going to undermine your
immediate and long-term health before long. So with that said,
there are several well described health-promoting
effects of caffeine ingestion. And once again, when I
say caffeine ingestion, I'm referring to that 1 to
3 milligrams per kilogram of body weight dosage. There are really nice studies
showing that being a regular consumer of caffeine can help
offset some of the probability, some of the probability
of developing Parkinson's and maybe
Alzheimer's-related dementia as well.
These are not terribly
controversial data because of the
fact that caffeine is known to increase the
release of those catecholamines, dopamine, epinephrine, and
norepinephrine, as well as acetylcholine. All those neurotransmitter
and neuromodulator systems are the ones that are
known to be defective in Parkinson's and
Alzheimer's, although there are other transmitter
and hormone systems that are defective as well. There are beautiful reviews
on the neuroprotective effects of caffeine and
neurodegenerative diseases. They're quite extensive. And I'll just refer you to one
and the references therein, and we'll provide a link to
this in the show note caption. So the title as the
topic at hand suggests is the neuroprotective
effects of caffeine and neurodegenerative diseases. This was published in 2016. I'm sure there have been
other reviews since then, but it includes many, many
quality references and studies, both in animals and in
humans, pointing to the fact that specific enzymes
that are associated with the health of, in
particular, dopamine neurons are made more robust by
regular ingestion of caffeine.
It also points to the
fact that the increase in dopamine receptors
that is induced by regular ingestion of caffeine
that I referred to earlier is another way in which
dopamine, however many dopamine neurons remain around in people
with Parkinson's or people who are aging that lose
dopamine neurons naturally, that dopamine can have
its maximal effect because of the increase in receptors for
dopamine that caffeine induces. And there are other
biological mechanisms that further
support why caffeine ought to be
neuroprotective, including its effects on the
acetylcholine system, which is one of the major
systems disrupted in Alzheimer's dementia.
So in other words, it
makes perfect sense as to why caffeine would
be neuroprotective. Caffeine has also been
shown to diminish headache, particularly when taken in
combination with aspirin. And that's because of the
effects of caffeine and aspirin on blood flow. There's also evidence
that caffeine can provide brief but
substantial relief from asthma. So I wouldn't want people
to rely on caffeine as a lifesaving approach
to an asthmatic attack. That said, for people that
suffer from minor asthma, that caffeine intake– again, of the dosages
that we talked about before has been
shown to alleviate some of the major symptoms
of asthma for anywhere from one to four hours. And I know this is of relevance
to a lot of people out there. Because caffeine increases
the catecholamines and in particular because
caffeine increases dopamine transmission in
the prefrontal cortex– this area of the brain that's
associated with focus and rule setting and context
and task switching– caffeine is known to
improve focus and alertness, in particular, in
people who have symptoms of ADHD or other
attention and focus issues.
Now caffeine alone
does not appear to be as potent for
the treatment of ADHD as are things like Ritalin,
Adderall, modafinil, or modafinil and Vyvanse. If you would like a sort
of head by head comparison of prescription
drugs, supplements, and things like
caffeine as well as coverage of behavioral tools
and nutritional tools, et cetera that can positively offset
some of the symptoms of ADHD, please see the episode
that I did on ADHD. Again, that's available at
hubermanlab.com in all formats. But that said, caffeine
does increase focus, and it does it through a
number of different mechanisms, not the least of which is to
increase dopamine transmission in the forebrain just as a drug
like Ritalin or Adderall would, although not to the same
extent as a drug like Ritalin or Adderall does.
Before we close today, I do
want to just briefly return to the reinforcing
effects of caffeine that we talked about earlier. This study on the
honeybees that showed that bees prefer certain vectors
because they contain caffeine. Even though they are not aware
that those vectors contain caffeine, they just come to like
the feeling that those nectars provide them so much
that they associate that in a subconscious way with
the flowers themselves, and they come to
like those flowers. Or human beings. For instance, children that
ingest caffeinated beverages come to adore the taste
of those beverages. And beautiful studies have been
done that describe how children and adults truly cannot
distinguish between the taste of a caffeinated and
noncaffeinated beverage. And caffeine can be placed
into essentially any beverage in order to give us a preference
for that beverage or food.
In fact, the studies have
been done with yogurt. If you put caffeine into
yogurt of different flavors– even plain yogurt which
most kids don't like– they will come to prefer
whatever flavor contain the caffeine even
if then you remove the caffeine from that flavor. Now eventually, their
preference for that flavor will be extinguished,
but all of this is just to say that so many
of the things that we like, whether or not it's coffee or
tea or a given flavor of food or a given experience
or even exercise, occur because we ingest
caffeine in conjunction with those activities. Now these are not tricks
that your nervous system plays on you. These are real
neurochemical-reinforcing effects. And I think that we
would all do well to think about and to leverage
these reinforcing effects much in the same
way we would do well to think about and hopefully
not leverage aversive effects of certain compounds, right? The simple way to put
this is I or anyone could get you to dislike
something, someone, or some place by making you feel
slightly less good, lower mood.
I don't even have to make you
feel nauseous but less good after ingesting
something or having a certain kind of interaction or
being in a certain environment, very straightforward to do
that, because of the way that your nervous system
is wired for conditioning. However, there's the
positive side of all this, which is that it's very
straightforward to reinforce the experience of a given
food, including its taste, but all the context around it,
the container, the texture, the people you consume it
with, where you consume it, et cetera. For instance, I
wonder why we are not pairing caffeine with broccoli. And here I'm not suggesting
that people actually do that experiment or
play that trick on people, but you have to sort of
imagine that, if caffeine is this incredible reinforcer
of all sorts of things, in particular, things that we
ingest and would want to ingest more of if it's paired
with caffeine, well then, you actually can use
caffeine as a tool to increase reinforcement
of different things. And you can avoid caffeine as a
way to further reinforce things that you would like to stop. And here I'd like to just give
the example of sugar cravings.
A lot of people ask me, how
do I avoid sugar cravings? I've talked about the use
of L-glutamine for that. I've talked about
making sure you're getting enough essential fatty
acids and essential amino acids as a way to reduce
sugar cravings. Please note,
however, that if you are somebody who likes to have
your sugar, whether or not it's a piece of chocolate
or your dessert, et cetera– I'm not saying that's
bad, but if you're trying to reduce your sugar
cravings, ask yourself, are you ingesting sugar
along with caffeine? Could be the caffeine contained
in that sugar-containing food like chocolate. Or it could be
that you're having a cup of coffee along
with your pastry, and then you're struggling
with sugar cravings.
Well, think about it. You're not just being reinforced
by the sugar and the effects of sugar on dopamine
which are real and both conscious
and subconscious through the gut to the
brain dopamine system and direct on the
brain dopamine system. But by coingesting
caffeine, you are also further enhancing the
reinforcing effects of sugar. The flip side to all of this
is that you could use caffeine as a way to increase your
appetite for certain things. I actually know somebody. I won't reveal who
this person is, but they are quite
prominent podcaster who ingests 125 to 150
milligrams of in tablet form along with herbal
tea and use this as a way to develop a
preference for herbal tea because they found that
coffee was giving them other effects that
weren't good for them. So it works quite
well in animals, and it works quite
well in insects. And it works quite
well in humans. I suppose animals,
insects, and humans are all animals at the end of
the day, so no surprise there. But it all underscores the
extent to which caffeine is an absolutely
fascinating molecule.
I mean, its ability to
offset the sleepiness system, if you will, this
adenosine system, and to control our
schedules in that way to essentially take a
withdrawal against the bank that is adenosine and
then pay that back later in the form of
getting sleepy later as opposed to when we
want to be alert, its ability to enhance
focus, alertness, and mood. And if taken after trying to
learn something and remember it, to enhance
memory, especially. And its ability to increase
VO2 max, increased strength. We didn't even talk
today about it, but I'll just briefly
mention that caffeine ingested in the sorts of
doses we talked about earlier. Because its effects on
the neuromuscular system and the calcium system
associated with neuromuscular exertion and fatigue can
increase peak power output and muscle contractability. It's enhancing
performance there as well. And, of course, caffeine
does a number of other things just generally related to
overall and basal level of mood and alertness, not
the least of which are these increases in dopamine.
So caffeine is really
an incredible molecule. It's affecting all these
various neurotransmitter systems but not haphazardly. It's increasing dopamine and
acetylcholine in the forebrain to increase attention. It's reducing fatigue. It's improving mental
and physical performance for some obvious and some
not so obvious reasons. And what I think is among the
more miraculous and powerful effects of caffeine, it is
a potent, potent, potent reinforcer of things, foods,
people, and experiences. And it's one that you can
leverage in any direction that you like once
you understand the way that caffeine exerts
those reinforcing properties. So today, I've really tried
to cover as much as I could about the mechanisms of caffeine
action in the brain and body, as well as tools and
schedules and dosages in which you can leverage
caffeine in order to meet your
physical performance, mental performance, and
frankly mental health, and overall health goals. If you're learning from
and/or enjoying this podcast, please subscribe to
our YouTube channel.
That's a terrific zero-cost
way to support us. In addition, please
subscribe to the podcast on both Spotify and Apple. And on both Spotify
and Apple, you can leave us up to
a five-star review. If you have questions for us
or comments about the podcast or guest that you'd like me to
interview on the Huberman Lab podcast, please put those in
the comment section on YouTube. We do read all the comments. In addition, please
check out the sponsors mentioned at the beginning and
throughout today's episode. That's the best way to
support this podcast. If you're not already following
Huberman Lab on social media, we are Huberman Lab
on all platforms, so that's Instagram, Twitter,
LinkedIn, and Facebook. And all of those places,
I describe science and science-related
tools, some of which overlap with the contents
of the Huberman Lab podcast, but much of which is distinct
from content on the Huberman Lab podcast. So again, it's Huberman Lab
on all social media platforms. During today's episode and
on many previous episodes of the Huberman Lab podcast,
we discuss supplements.
While supplements aren't
necessary for everybody, many people derive
tremendous benefit from them for things like sleep, hormone
augmentation, and focus. If you'd like to see the
supplements discussed on various episodes of
the Huberman Lab podcast, please go to
livemomentous.com/huberman. We partnered with
Momentus because they are extremely high quality,
they ship internationally, and they formulated supplements
in the precise ways that are discussed as optimal to
take for various outcomes here on the Huberman
Lab podcast. If you haven't already
subscribed to the Huberman Lab podcast newsletter, it
is a monthly newsletter that includes summaries
of podcast episodes as well as tool kits, all of
which are completely zero cost.
All you have to do is provide
your email to sign up. We do not share your
email with anybody. You do this by going
to hubermanlab.com. Go to the menu and tap
down to newsletter. Provide your email. You'll get a confirmation link. Click on that link
and you'll receive our monthly newsletters. And you can also access any
of the previous newsletters that we've released, including
the tool kist for sleep, for fitness, deliberate
cold exposure, and so on. By going to hubermanlab.com,
go into the Menu, go into Newsletter,
and there you'll see those as immediately
downloadable PDFs. Thank you for joining me
for today's discussion about caffeine,
both its mechanisms, and its many powerful uses.
And last but
certainly not least, thank you for your
interest in science. [MUSIC PLAYING].
