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EPISODE LINKS:
Andrew's YouTube: https://www.youtube.com/channel/UC2D2CMWXMOVWx7giW1n3LIg
Huberman Lab Podcast: https://hubermanlab.libsyn.com/
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OUTLINE:
0:00 - Introduction
1:28 - Why do humans need sleep?
8:24 - Temperature
11:12 - Optimal temperature for sleep
16:15 - Sleep anxiety
22:19 - 8 hours of sleep
24:55 - Nap
30:43 - Goggins Challenge
46:06 - Breathing while running
50:54 - Anger
54:11 - Testosterone
59:27 - Fasting
1:07:32 - Keto
1:10:22 - Meat
1:16:02 - Nutrition
1:17:28 - Dreams
1:25:35 - REM sleep
1:31:37 - Psychedelics
1:43:01 - DMT
1:47:35 - Creativity
1:51:09 - Pushing the limits of the human mind
1:56:19 - Neuroplasticity
2:00:56 - Neuroscience and AI
2:05:38 - Eye tracking
2:14:52 - New podcast on neuroscience
2:29:23 - Clubhouse
2:41:32 - Elon Musk

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The following is a conversation with Andrew Huberman, his second time on the podcast.

He's a neuroscientist at Stanford, a world-class researcher and educator, and now he has a new podcast on YouTube and all the usual places called Huberman Lab that I can't recommend highly enough.

Quick mention of our sponsors, Masterclass Online Courses, 4 Sigmatic Mushroom Coffee, Magic Spoon Low Carb Cereal, and BetterHelp Online Therapy.

Click the sponsor links to get a discount.

By the way, Masterclass is testing to see if they want to support this podcast long-term.

So if you're on the fence, now is the time to sign up.

And I'm pretty sure Andrew will have a neuroscience masterclass on there soon enough, though his podcast is basically a weekly masterclass in itself.

As a side note, let me say that Andrew is a friend and a new collaborator.

We're working on a paper together about a topic we're both really passionate about at the intersection of neuroscience and machine learning.

But that's probably many months away from being published.

Still, I'm really excited about this work.

He's 1 of the smartest and kindest people I have the pleasure of talking to on this podcast.

So I hope we'll talk many more times in the future.

If you enjoy this thing, subscribe on YouTube, review it on our podcast, follow on Spotify, support it on Patreon, or connect with me on Twitter, Alex Friedman.

And now, here's my conversation with Andrew Huberman.

Okay, well, the answer I'll start with is the 1 that I always default to when there's a why question, which is I wasn't consulted at the design phase.

So I wriggle my way out of giving a absolute answer, right?

But there's 1 mechanism that's very clear, that's super important, which is that the longer we're awake the more adenosine accumulates in our brain And adenosine binds to adenosine receptors, no surprise there.

And it creates the feeling of sleepiness, independent of time of day or night.

1 is we get sleepy as adenosine accumulates.

The longer we've been awake, the more adenosine is accumulated in our system.

But how sleepy we get for a given amount of adenosine depends on where we are in this so-called circadian cycle.

And the circadian cycle is just this very, very well-conserved oscillation.

It's a temperature oscillation where you go from a low point, typically if you're awake during the day and you're asleep at night, your lowest temperature point will be like 3 a.m., 4 a.m.

And then your temperature will start to creep up as you wake up in the morning.

And then it'll peak in the late afternoon and then it'll start to drop again toward the evening and then you get sleep again.

That oscillation in temperature takes 24 hours.

And I don't, even though I wasn't consulted at the design phase, I do not think it's a coincidence that it's aligned to the 24 hour spin of the earth on its axis.

And the fact that we tend to be bathed in sunlight for a portion of that spin and in darkness for the other portion of that spin.

So there are 2 mechanisms, the Adenosine accumulation and the Circadian time point that we happen to be at.

And Those converge to create a sense of sleepiness or wakefulness.

The simple way to reveal these 2 mechanisms to uncouple them is stay up for 24 hours.

And you will find that even though you've been, let's say you stay up midnight, 2 a.m., 3 a.m., provided you're on a regular schedule, like that I follow, not like the kind that you follow.

You get, I will get very sleepy around 3, 4 a.m.

Which is my normal wake up time, I'll start to feel more alert, even though adenosine has been accumulating further.

So adenosine is higher for me, the longer I stay up, and yet I feel more alert than I did a few hours ago.

And that's because these are 2 interacting forces.

So adenosine makes you sleepy, and then just how sleepy or how awake you feel also depends on where you are in this temperature oscillation that takes 24 hours.

So there's a bunch of oscillations going on and then they kind of, through the evolutionary process, have evolved to all be aligned somewhat and they interplay.

So you said your body temperature goes up and down.

There's chemicals in your brain that oscillate, and then there's the actual oscillation of the sun in the sky.

So all of that together has some impact on each other, and somehow that all results in us wanting to go to sleep every night.

Right, so, and we can get right into the meat of this, So I guess we just dove right in.

But the, so the temperature oscillation is the effector of the circadian clock.

So every cell in our body has a 24 hour rhythm that's dictated by genes like clock, per, b-mal.

This is 1 of the great successes of biology, they give a Nobel prize to Ruppert.

I don't know if Ruppert got it, forgive me, but sorry if you got it, Steve, congratulations.

If you didn't, I'm sorry, I wasn't on the committee.

Nonetheless, did beautiful work, Steve Ruppert and others, but Mike Roshbosch and like other people worked out these mechanisms in flies and bacteria and mammals, there are these genes that create 24 hour oscillations in gene expression, et cetera, in every cell of our body.

But what aligns those is a signal from the master circadian clock, which sits right above the roof of the mouth called the suprachiasmatic nucleus.

And that clock synchronizes all the clocks of the body to this general temperature rhythm by way of controlling systemic temperature, which makes perfect sense.

If you want to create a general oscillation in all the tissues and organs of the body, use temperature.

And so that work on temperature, if people want to explore it further, was Joe Takahashi, who was at Northwestern now at UT, Southwestern in Dallas.

And it is absolutely clear that humans do better on a diurnal schedule, sorry Lex, than a nocturnal schedule.

Because you could say, well, provided I sleep and push adenosine back downhill, which is what happens when we sleep, adenosine is then reduced.

And provided I am on more or less a 24 hour schedule, why should it matter that I'm awake when the sun's out and I'm asleep when the sun is down?

But it turns out that if you look at health metrics, people that are strictly nocturnal do far worse on immune function, on metabolic function, et cetera, than people who are diurnal, who are awake during the daytime.

And animals that are nocturnal, it's the opposite.

And animals that are so-called crepuscular, which tend to be active at dawn and at dusk.

I won't go down that rabbit hole, but these are animals whose visual systems operate best.

They tend to be predators like mountain lions.

They have optimized their waking times for the times when the animals they eat can't see well in those light conditions.

But given the rod cone ratios in their eyes, that the mountain lion is picking off.

It's like when you see a special forces and they are looking through night vision goggles and they have a clear advantage, right?

That's basically what it's like to be a mountain lion as opposed to a bunny rabbit.

Would you say that a lot of these cycles evolved in the predator-prey relationships of the different, throughout the food chain?

So it's basically all somehow has to do with survival in this complicated web of predators and prey?

There had to have been a time in which humans being awake and active at night, as opposed to during the day, led to higher levels of lethality.

And probably particular in kids, You imagine kids running around in the dark and getting where there are a lot of animals that can see really well under those conditions and humans can't.

Even if you're carrying a torch, I mean, the range of illumination on a torch is nothing compared to what a nighttime predator, like a large cat or something can do.

I mean, they basically, they can see everything they need to in order to eat us and not the other way around.

So 1 fascinating thing you said is, that blew my mind and we went right past it, which is the temperature is a really powerful, like if you were to think about the ways that different parts of the body, different systems in the body would communicate with each other, temperature would be a really good 1.

And that just, I mean, maybe it's obvious, but it kind of blew my mind just now, that yeah, these systems are all distributed.

And they have to kind of, they're not actually sending signals, but they're coordinating, they need some sort of universal thing to look at in order to coordinate.

And temperature is a nice 1 to build around.

And that way you could control the behavior of all these different systems by controlling the temperature.

It's attractive to think of a mechanism where this master circadian clock secretes a peptide or something that goes and locks the receptors in all the cells and gets it just right.

But that leaves far too much room for variability, binding affinities, cells in a lot of parts of our body are at different stages of maturation.

They're turning over, liver cells and so forth.

And for instance, we have a clock in our gut and in our liver, such that if we were just take out your liver and put it on a table and just look at the expression of these genes, it would be in a 24 hour oscillation on its own, it's independent, but something has to entrain them and keep them all synchronized.

And so it's not obvious that it would be temperature.

Takahashi's great gift to biology was to show that all the stuff coming out of this master circadian clock at the end of the day, that's a weird statement, no pun intended, at the end of the day and the night, at the end of the story, it all boils down to making sure that the temperature of tissues oscillates in the same fashion.

That's blowing my mind and thinking like what other mechanism could possibly exist to create that kind of oscillation.

Well, you're Russian, it's cold in Russia for a lot of the year.

The hibernation signal in certain animals is a remarkable signal.

There are peptides secreted from this very same clock that in animals like ground squirrels or bears, they go into a kind of a torpor where everything, reproduction, metabolism, everything is reduced while they're in their cave.

They don't actually stay asleep all of winter, that's a myth.

And they actually do these very dramatic and periodic arousals from hibernation where they just shake and shake and shake, it looks like a seizure, and then they go back under into the torpor.

But that's different because that's about shutting down the whole system.

It's clear that having these very regular oscillations every 24 hours is essential for everything from metabolism to reproduction.

Is there an optimal temperature for sleep that I should mention, I think your latest episode, and people should go check out helixsleep.com slash Huberman to support Andrew.

I mean, the amazing thing about the stuff they create, and oh, and yes, you have a new podcast.

That's amazing, and this past month, he did a whole series on sleep, which people should definitely check out.

There's some podcasts that come out that just make me wanna be a better human being by just the quality.

3 blue, 1 brown, Grant Sanderson is like that for me.

Just like, wow, this is education is best.

So Andrew symbolizes that, captures that brilliantly, so go support the sponsor so he doesn't stop doing the thing.

So they, I think they have a cooling pad too.

They've been, they send me a mattress and it's been, I've never, listen, I used to sleep on the floor.

But so like I would have never bought a nice mattress.

But it was a game changer to be able to control temperature.

Well, you want the brain and nervous system and rest of the body needs to drop by about anywhere from 2 to 3 degrees in order to get into your deepest sleep and transition to sleep.

You don't want to be cold that you're bothered and can't fall asleep, but that's why some people like it really cold in the room and under a warm blanket or with socks on for some people, that can be good because this temperature oscillation is such that as your temperature is dropping, that correlates generally with the most sleepy phase of your circadian cycle.

So cool is better for falling and staying asleep and sleeping deeply.

And then I guess like that's what 8 Sleep showed.

They have like an app, it warms back up to wake you up.

The idea that, I haven't actually used it, I'm like This is stupid.

People say it works, but I just keep it the same temperature throughout the night.

But warming it up, I guess, wakes you up, which is fascinating.

Yeah, because the wake-up signal is, It's interesting to think about it.

It's not just correlated with an increase in body temperature.

The increase in body temperature is triggering the release of cortisol from your adrenals, and that's the wake up signal.

Do you think it's absolute temperatures we're talking about, or is it just even relative?

Well, everyone's gonna have slightly different basal temperature.

And there are theories that body temperature overall has been dropping in the last 50 years or so.

I doubt that's true for somebody who is athletic like you and is, you know, young and healthy.

But basically the coldest period of that 24 hour cycle is when you are going to be sleepiest.

There's actually a period within that 24 hour cycle, it's a time point called your temperature minimum.

And your temperature minimum tends to be about 2 hours before your typical wake up time.

I'm not talking about the wake up time in the middle of the night where you go use the bathroom or where you set an alarm to go catch a flight.

I mean, if you were to just allow yourself to sleep without a clock for a few days, measure when you typically wake up, 2 hours before then is your temperature minimum.

And that temperature minimum turns out to be a very important landmark in your circadian cycle because it turns out that if you get bright light in your eyes in the hours immediately before your temperature minimum.

So 2 to 4 hours or anytime within the 2 or 4 hour window before that temperature minimum, you are going to what's called delay your circadian clock.

The next day, that whole oscillation is going to move forward.

It'll make you want to go to sleep later and wake up later.

Whereas if you get bright light in your eyes in the hours after that temperature minimum.

So let's say for me, typical wake up time is 6 a.m.

My temperature minimum somewhere around 4 a.m.

If I get bright light in my eyes, 5 a.m., 6 a.m., 7 a.m., it's going to advance that oscillation so that I'll want to go to bed earlier and wake up earlier the subsequent nights.

So you might say, wait, but most nights I go to sleep and wake up at more or less the same time.

And that's because the same thing is happening on both sides.

You are both advancing your clock a little bit and assuming that you're looking at light in the evening, you're also delaying your clock a little bit.

So you get kind of captured in between and then your rhythm more or less oscillates at the same period, as we say, as the spin of the earth.

Unless you're like you where you're, I get text messages from you sometimes at odd hours and if you're on the East Coast, then I know that you had to have been pulling basically an all nighter.

That's the interesting point about the messiness of sleep.

So most people seem to perform the best when they have like a regular sleep schedule.

I perhaps am the same, but I don't know that.

And I tend to believe that you can also perform relatively optimally with chaos of sleep, of like a weird soup of like power naps and all-nighters and all of that, as long as you're like happy doing what you love.

And maybe you can Tell me what you think about this.

I tend to, for myself, try to minimize stress in life.

So what I found for myself with diet, with sleep, is that if I obsess about it being perfect, then I'll actually stress quite a bit when it's not.

Like I'll feel shitty when I don't get enough sleep because I know I should be getting more sleep as opposed to the actual physiological effects of not getting enough sleep.

I find if I just accept whatever the hell happens, happens and smile and just, you know, take it all in, like David Goggins style, like if it sucks, it's even better or what is it?

Right, I think that several things that you said they're important, but I agree that 1 can have a dysregulated sleep schedule and still be a happy person and productive.

In much of my life, I've pulled all-nighters and slept weird schedules.

I think many people can probably relate to going to sleep, waking up 4 hours later, being up for an hour or 2 on your computer, then going back to sleep and getting amazing sleep the next day functioning.

I think we've, I think it's important that people have highlighted the importance of sleep and getting enough rest.

And now I'm editorializing a little bit, but I think that we've created this anxiety about sleep that if we don't sleep enough, we're going to get dementia.

If we don't get sleep, then the reproductive axis is gonna completely crash.

You know, there's a lot of evidence to the contrary and as well, just based on personal experience and based on the fact that sure, It may be that a solid 8 hours with no interruptions in there or 9 or 10 could do great benefit, but you can do really well if you do what you say, which is you wake up, you don't want to start stressing about it, creating this meta stress about sleep.

Being happy is actually 1 of the most powerful things that you can do, not allowing yourself to go down that rabbit hole of stress for the following reason.

A lot of our fatigue is not due just to the buildup of adenosine or time of day, the circadian thing we were talking about earlier.

An additional factor is that effort is related to the release of epinephrine, of adrenaline in our brain and body.

At some point, those levels get so high that we get stressed mentally, we get stressed physically and we want to give up.

There are good data published in Cell showing that that signal, the epinephrine signal is eventually accumulates and there's a quick point.

Dopamine, the molecule of pursuit and reward and feeling good, resets our ability to be in effort.

In fact, a lot of people don't know this, but dopamine is actually what epinephrine is made from.

If you look at the biochemical cascade, it starts with tyrosine, which is rich in, found in red meats and things of that sort.

And tyrosine is eventually converted through things like L-DOPA into dopamine.

So, I mean, this sounds kind of new agey, but happiness, joy, and pleasure in what you're doing creates a chemical milieu that provides more of the chemicals that allow for effort.

It's in every decent neuroscience textbook.

They just don't talk about the happiness part.

So I think that limiting your stress and at least recognizing, okay, if you're pulling an all nighter, you're somehow on messed up sleep, that there is going to be a point in that 24 hour cycle where your brain is not trustworthy, where your mental state is not worth placing too much weight on because you are near that temperature minimum.

And near that temperature minimum, which is correlates to that 2 hour, about 2 hours before you would normally wake up, the brain is hobbling along.

And anything you feel or think at that time should not be given too much value.

But if you can trick yourself into thinking that's the pleasure point, you afford yourself a huge advantage.

There's a study done by a colleague of mine at Stanford that showed that positive anticipation about the next day events actually is a powerful metric for creating quality sleep, even if the sleep is very reduced.

And a lot of people are going to, you know, might be critical of this.

So I just want to make sure that, so this was work done out of Harvard Medical.

It was Bob Stigold's lab and Emily Hoagland did this study that showed looking at OCHEM, performance on OCHEM scores.

Okay, so organic chemistry at Harvard's pretty tough subject, highly motivated, a number of very good control groups in this study.

What she showed was that consistency of total sleep duration was far more important for performance on these exams than total sleep duration itself.

So it's not that just getting more sleep allows you to perform better.

Consistently getting about the same amount of sleep is better for performance, at least on OCHEM, than just getting more.

That's interesting, so that's referring to more that there should be a consistent habit versus the total amount.

To me, the entirety of the picture of sleep is similar to nutrition in that it feels like there's so many variables involved and it's so person-specific.

So a lot of studies, I mean this is the way of science, has to look and aggregate the effects on sleep.

It doesn't focus on high performers, which are individuals ultimately.

The question isn't, so it's a very important question, is what kind of diet fights obesity, reduces obesity?

It's another question, what kind of diet allows David Goggins to be the best version of himself?

So these high performers in different avenues.

And the same thing with sleep, like people that tell me that I should get 8 hours of sleep.

It's like, it's, I mean, I get it, and they may be right, but they may be very wrong.

There's no evidence that 8 is better than 6, that you could very well do better on 6 than on 8.

There are a few other things that turn out to be strong parameters for success in this domain.

For instance, your entire life, waking or asleep, is broken up into these 90 minute ultradian cycles.

If you look at ability to attend or do math problems or do anything, you know, drive.

Performance tends to ramp up slowly within a 90 minute cycle, peak, and then come down at the end of that 90 minute cycle.

And in sleep, we go through these stage 1234, REM, et cetera.

Those on 90 minute ultradian cycles as well.

Ending your sleep after a 90 minute cycle, at the near the end of a 90 minute cycle, say at the end of 6 hours, in many cases is better for you than sleeping an additional hour, 7 hours, and waking up in the middle of an ultradian cycle.

And there are a few apps that can measure this based on body movements and things like that, that have your alarm go off at the end of an ultradian cycle.

And if you wake up in the middle of an ultradian cycle, sometimes, not always, you can be very groggy for a long period of time.

I certainly do better on 6 hours than I do on 7.

It feels great, but I haven't slept an entire 8 hours without waking up in the middle of the night at some point in, I don't know, forever.

It's probably some point in infancy, but, and I function well during the day.

I think that that's a big, that's an important parameter is how do you feel during the day?

Almost everybody experiences some sort of dip in energy in the late afternoon or what would correlate to their temperature peak.

And that's a good time of day to get either a 90 minute or less nap, or if you're not a napper or you can't nap, feet elevated has been shown to be good for clear out of some of this, the glymphatic system is this kind of like sewer system of the brain that you can clear stuff out.

So legs elevated, or 1 thing that I'm a big proponent of and that my lab has been studying is what I now call NSDR, non-sleep deep rest.

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Andrew Huberman: Sleep, Dreams, Creativity, Fasting, and Neuroplasticity | Lex Fridman Podcast #164