Huberman Lab - Using Science to Optimize Sleep, Learning & Metabolism

Welcome to the Huberman Lab Podcast,

where we discuss science

and science-based tools for everyday life.

I’m Andrew Huberman,

and I’m a professor of neurobiology and ophthalmology

at Stanford School of Medicine.

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.

Along those lines,

I want to thank the sponsors of today’s podcast.

Our first sponsor is Athletic Greens.

Athletic Greens is an all-in-one

vitamin mineral probiotic drink.

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 twice a day

is that it helps me cover

all of my basic nutritional needs.

It makes up for any deficiencies that I might have.

In addition, it has probiotics,

which are vital for microbiome health.

I’ve done a couple of episodes now

on the so-called gut microbiome

and the ways in which the microbiome interacts

with your immune system,

with your brain to regulate mood,

and essentially with every biological system

relevant to health throughout your brain and body.

With Athletic Greens, I get the vitamins I need,

the minerals I need,

and the probiotics to support my microbiome.

If you’d like to try Athletic Greens,

you can go to slash Huberman

and claim a special offer.

They’ll give you five free travel packs

plus a year supply of vitamin D3 K2.

There are a ton of data now

showing that vitamin D3 is essential

for various aspects of our brain and body health.

Even if we’re getting a lot of sunshine,

many of us are still deficient in vitamin D3.

And K2 is also important

because it regulates things like cardiovascular function,

calcium in the body, and so on.

Again, go to slash Huberman

to claim the special offer of the five free travel packs

and the year supply of vitamin D3 K2.

Today’s episode is also brought to us by Element.

Element is an electrolyte drink

that has everything you need and nothing you don’t.

That means the exact ratios of electrolytes are an element,

and those are sodium, magnesium, and potassium,

but it has no sugar.

I’ve talked many times before on this podcast

about the key role of hydration and electrolytes

for nerve cell function, neuron function,

as well as the function of all the cells

and all the tissues and organ systems of the body.

If we have sodium, magnesium, and potassium

present in the proper ratios,

all of those cells function properly

and all our bodily systems can be optimized.

If the electrolytes are not present

and if hydration is low,

we simply can’t think as well as we would otherwise,

our mood is off, hormone systems go off,

our ability to get into physical action,

to engage in endurance and strength

and all sorts of other things is diminished.

So with Element, you can make sure

that you’re staying on top of your hydration

and that you’re getting the proper ratios of electrolytes.

If you’d like to try Element, you can go to drinkelement,

that’s slash Huberman,

and you’ll get a free Element sample pack

with your purchase.

They’re all delicious.

So again, if you want to try Element,

you can go to slash Huberman.

Today’s episode is also brought to us by Thesis.

Thesis makes what are called nootropics,

which means smart drugs.

Now, to be honest, I am not a fan of the term nootropics.

I don’t believe in smart drugs

in the sense that I don’t believe

that there’s any one substance or collection of substances

that can make us smarter.

I do believe based on science, however,

that there are particular neural circuits

and brain functions that allow us to be more focused,

more alert, access creativity, be more motivated, et cetera.

That’s just the way that the brain works,

different neural circuits for different brain states.

Thesis understands this.

And as far as I know, they’re the first nootropics company

to create targeted nootropics for specific outcomes.

I’ve been using Thesis for more than six months now,

and I can confidently say that their nootropics

have been a total game changer.

My go-to formula is the clarity formula,

or sometimes I’ll use their energy formula before training.

To get your own personalized nootropic starter kit,

go online to slash Huberman,

take a three-minute quiz,

and Thesis will send you four different formulas

to try in your first month.

That’s slash Huberman,

and use the code Huberman at checkout

for 10% off your first order.

I’m pleased to announce that the Huberman Lab Podcast

is now partnered with Momentus Supplements.

We partnered with Momentus for several important reasons.

First of all, they ship internationally

because we know that many of you are located

outside of the United States.

Second of all, and perhaps most important,

the quality of their supplements is second to none,

both in terms of purity and precision

of the amounts of the ingredients.

Third, we’ve really emphasized supplements

that are single ingredient supplements,

and that are supplied in dosages

that allow you to build a supplementation protocol

that’s optimized for cost,

that’s optimized for effectiveness,

and that you can add things and remove things

from your protocol in a way

that’s really systematic and scientific.

If you’d like to see the supplements

that we partner with Momentus on,

you can go to slash Huberman.

There you’ll see those supplements,

and just keep in mind that we are constantly expanding

the library of supplements available through Momentus

on a regular basis.

Again, that’s slash Huberman.

Okay, let’s get started.

Today is episode three of the podcast,

and it is office hours.

Office hours, as many of you know,

it’s where students come to the office of the professor,

sit down and ask questions,

requesting clarification about things that were confusing,

or to simply go down the route of exploring a topic

with more depth and detail.

I asked for your questions to be listed

in the comment section of the previous two episodes

of the podcast on YouTube, as well as on Instagram.

And I, first of all, just want to thank you

for the many questions.

They are excellent.

We read them all.

We distilled from that large batch of questions

to two types of questions,

questions that were asked very often

and were liked very often,

with a little thumbs up like tab,

as well as questions that we thought could really expand

on the topics that we’ve covered previously.

And today we’re going to cover both of those.

If we did not get to your question,

please don’t despair.

We will keep track of those,

and we have several more episodes devoted to this topic

of sleep and wakefulness and learning

during the month of January,

maybe even leaking over a little bit

into the month of February.

So we have time.

That’s one of the unique formats of this podcast

is that we have time for dialogue.

We have time for your questions,

and we have time to really go deep into these topics.

It’s official, Costello’s sleeping in the background.

So if you hear snoring,

Costello is going to be keeping time

with his deep and melodic snoring.

There he goes.

So the questions that we received,

I batched crudely into a couple of different categories.

Light, exercise, supplementation,

temperature, learning, plasticity,

and mood and sort of mood-related disorders.

There were a lot of questions about those.

Before we begin any of this,

I want to point out something that I always say.

It sounds like boilerplate,

but it’s important not just to protect me,

but to protect you,

which is that I am not a physician.

I’m not a medical doctor.

I don’t prescribe anything,

including behavioral protocols.

I’m a professor, so I profess a lot of things

based on quality peer-reviewed studies.

You should take that information.

You should filter it through whatever it is

that you currently happen to be dealing with,

whether or not that’s health or illness.

You should consult with a licensed healthcare professional

before you add or remove anything

from your daily life protocol.

I’m not responsible for your health.

You are, so be smart with this information

and be a stringent filter, as we say.

Okay, very well.

Let’s get started on the actual material.

Somebody asked,

what is the role of moonlight and fire?

I’m presuming they mean fireplace or candle

or things of that sort, in setting circadian rhythms.

Is it okay to view moonlight at night

or will that wake me up?

Will a fire in my fireplace or using candlelight

be too much light?

Great question.

Also offers me the opportunity to share with you

what I think is a quite beautiful definition

of what light is in a quantitative sense.

So I’ve mentioned a few times the use of apps

and light meters and things to measure things like lux,

which sometimes are also described in terms of candelas.

So those are the two units for measuring light intensity.

Typically lux, L-U-X, is the unit.

And so before we go forward and discuss this many lux

or that many lux, I want to just tell you what a lux is,

because it relates to this question.

One lux equals the illumination of one square meter surface

at one meter away from a single candle.

Think about that.

So somebody actually decided at some point

that the amount of illumination at one square meter surface,

one meter away from a single candle, that equals one lux.

So when we talk about 6,000 lux of light intensity

or 10,000 lux of light intensity,

now you have a kind of a reference or a framework

that would be the equivalent of,

you could think of it as 6,000 candles

all with their light intensity shown on one square meter

from one meter’s distance away.

Or of course, if it was a different number of lux,

it would be a different number of candles.

So you get the idea.

Here’s the great thing.

Turns out that moonlight, candlelight,

and even a fireplace,

if you have one of these roaring fires

going in the fireplace,

do not reset your circadian clock at night

and trick your brain into thinking that it’s morning.

Even though if you’ve ever sat close to a fireplace

or even a candle, that light seems very bright.

And there are two reasons for that that are very important.

The first one is that these neurons in your eye

that I discussed in the previous episode,

these melanopsin ganglion cells,

also called intrinsically photosensitive ganglion cells,

those cells adjust their sensitivity across the day.

And those cells respond best to the blue-yellow contrast

present in the rising and setting sun,

so-called low solar angle sun,

also discussed in the previous episode.

But those cells adjust their sensitivity

such that they will not activate the triggers in the brain

that convey daytime signals when they view moonlight,

even a full moon, a really bright moon, or fire.

Now, this does raise an interesting kind of thought point,

which is a lot of people have talked about lunacy

and the fact that when there’s a full moon out,

people act differently and behave differently.

There’s a lot of lore around that.

There’s actually a little bit of quality science around that

that maybe we can address in the future.

But moonlight is typically not going to wake us up too much,

except maybe if the moon is really full and really bright,

there’s possibility for that.

So provided you’re not going to burn down

the structure you’re in,

you’re not going to burn down the forest,

enjoy your fireplaces, enjoy your lights from candles,

and those are perfectly safe

without disrupting your circadian rhythm.

Because we talked about just how crucial it is

to avoid bright lights

between the hours of about 10 p.m. and 4 a.m.,

except when you need to view things for sake of safety

or work and so forth.

I also received a lot of questions about red light.

Now, I think I was asked those questions

because red light is used

in a number of different commercial products

where these products tend to include a sheet

of very bright red lights

that one is supposed to view early in the day.

And there are various claims

attached to these red light devices,

that they improve mitochondrial function,

that they improve metabolism.

I’m going to be really honest,

and I can’t name brands,

and I’m not going to name particular studies,

because what I’m about to say about these studies

is not particularly unkind,

but let’s just say that none of the studies that I’ve seen,

except for one that I’ll talk about in a moment,

pointing to the positive effects of red light

on the visual system,

are published in blue ribbon journals.

They tend to be published in journals

that I had to work hard to find.

I’m not sure what the peer review instringency level is.

Now, that’s not to say red light isn’t beneficial,

because there is one study in particular

that came from Glenn Jeffrey’s lab

at the University of College London.

It was published last year.

Glenn is somebody I happen to know.

He has an excellent reputation, excellent vision scientist.

What this study essentially showed,

and again, this is a study that I very much like the data

and think it was done with very high standards.

What this study shows is that viewing red light

for a few minutes each morning

can have positive effects on mitochondria

in a particular retinal cell type

that tends to degenerate or decline in function

with age in humans,

and that cell type is the photoreceptor.

The photoreceptor is a type of cell in your eye

that sits at the back of the eye.

It’s kind of some distance away from the ganglion cells,

and it’s the cell that converts light information

into electrical signals that the rest of the retina

and brain can understand.

These are vitally important cells.

Without them, people are blind,

and many people’s vision gets worse with age,

in particular, age-related macular degeneration,

but also related to some other factors,

including photoreceptor functionality

just getting worse with time,

and what Glenn showed was that red light flashes

delivered in particular early in the day,

but not late in the day,

can help repair the mitochondria.

Now, this study needs more support

from additional studies, of course.

They are doing a clinical trial.

They did report on what, I think it was 12 patients,

and so the work is ongoing, but that was very interesting,

and it points to some potentially

really useful things about red light.

However, most of the questions I got about red light

for sake of office hours

were about the use of red light later in the day,

so here’s the deal.

In principle, red light will not stimulate

the melanopsin retinal neurons

that wake up the brain and circadian clock

and signal daytime.

However, most of the red lights,

in particular, the red lights

that come on these sheets of these products

that people are supposed to view

in order to access a number of proclaimed health effects,

those are way too bright

and would definitely wake up your body and brain,

so if you’re going to use those products,

and I’m not suggesting you do or you don’t,

but if that’s your thing,

you would want to use those early in the day.

Who knows, you might even derive some benefit

on mitochondrial function in these photoreceptors,

but if you’re thinking about red light

for sake of avoiding the negative effects of light

later in the day and at night,

then you want that red light to be very, very dim,

certainly much dimmer than is

on most of those commercial products.

Now, do you need red lights?

No, although red lights are rather convenient

because you can see pretty well with them on,

but if they’re dim,

they won’t wake up the circadian clock,

they won’t have this dopamine disrupting thing

that we talked about in the previous podcast.

So there’s a role for red light

potentially early in the day

and for mitochondrial repair in the photoreceptors,

there’s a role for dim red light

later in the day and at night.

So you’re starting to notice a theme here,

which is that there’s no immediate prescription

of look at these lights,

it’s look at these lights potentially

if that’s what you want to do at particular times of day

and with particular intensities.

It brings us back to the blue light issue,

which is so many people are obsessed

with avoiding blue light,

but you actually want a ton of blue light

early in the day and throughout the day,

so don’t wear your blue blockers then,

or maybe even don’t wear them at all.

And at night, it doesn’t matter if you have blue blockers on

if the lights are bright enough,

then you’re still going to be activating

these cells and mechanisms.

I just want to add something

since about the science behind the blue blocker confusion.

So these melanopsin retinal cells do react to blue light,

that is the best stimulus

for one of these melanopsin cells,

which led to the belief that blue blockers

would be a good thing for preventing resetting

of the circadian clock at night

and deleterious effects of screens, et cetera.

However, the people that made these products

failed to actually read the papers start to finish,

or if they did, they didn’t comprehend a critical element,

which is that most of those papers early on

took those neurons out and put them in a dish.

And when they did that,

they divorced those neurons

from their natural connections in the eye.

Turns out in your eye and my eye right now,

because that’s what we care about,

these cells exist and these cells respond to blue light,

but also to other wavelengths of light

because they not only respond directly to light

as they do in a dish,

they also respond to input from photoreceptors.

So if you talk to anyone in the circadian biology field,

they’ll tell you, oh yeah,

this blue light thing has really gotten out of control

because people assume that blue light is the culprit

because blue light is the best stimulus.

That doesn’t mean that blue light is the only stimulus

that will trigger these cells, okay?

So like many things,

a scientific paper can be accurate without being exhaustive.

And a lot of claims about products

can be accurate, but not exhaustive.

So blue light during the day is great.

Get that screen light, get that sunlight,

especially getting overhead lights.

I talk about all this in the previous podcast.

But at night, you really want to avoid those bright lights.

And it doesn’t matter if it’s blue light or something else.

And so there was a real confusion about the papers

and the data when most of those product recommendations

were made.

Okay, while we’re on that topic,

let’s talk about light in other orifices of the body.

I made kind of a joke about this the last podcast episode,

but a couple of people wrote to me and said,

well, I’ve seen some claims that light delivered

to the ears, into the ears or the roof of the mouth

or up the nose can be beneficial

for setting circadian rhythms.

You know, not directly anyway.

And this is a great opportunity for us to distinguish

between what is commonly called the placebo effect,

but a more important way to think about any manipulation,

behavioral or otherwise, that you might do

is the difference between modulation and mediation.

There are a lot of things that will modulate your biology.

Putting a couple of lights up your nose,

please don’t do this, might modulate your biology

by way of the stress hormone that’s released

when you stuff those things up your nose.

Remember earlier, previous podcast,

I said that virtually anything will phase shift

to your circadian rhythm

if it’s different and dramatic enough.

So the question is, is it the light delivered up the nose

or through the ears or some other orifice

that’s mediating the process?

Is it actually tapping into the natural biology

of the system that you’re trying to manipulate?

And this is where I like to distinguish

between real biology and hacks.

I don’t like the word hack

or frankly neurohacking or biohacking.

I just don’t like the term

because a hack is using something for a purpose

for which it was not intended, right?

But where you can kind of, it’s a kind of a cheat

and that’s not how biology works well.

So I try and distinguish between things

that really mediate biological processes

and things that modulate them.

There are a number of commercial products out there

with some studies attached to them

claiming that light delivered to the ears

or wherever can adjust your wakefulness

or adjust your sleep.

I’ve looked at those papers.

Again, I’m probably gonna lose some friends by saying this

but maybe I’ll gain a few as well.

Not blue ribbon journals, frankly.

Oftentimes read the small print.

There was a conflict of interest clause there

related to commercial interests.

If somebody disagrees with me outright on this

and can send to me a peer reviewed paper

or publish in a quality journal about light delivered

anywhere but the eyes of humans

that can mediate circadian rhythms, wakefulness, et cetera.

I’m more than happy to take a look at that

and change my words and stance on this

and do it publicly, of course.

But until then, I’m guessing that the proper controls

were not done of adjusting for heat that could be delivered

which can definitely shift circadian rhythms.

We’re gonna talk about temperature

and other things like that.

So light to the eyes folks

is where these light effects work in humans.

In other animals,

they have extraocular photoreception, in humans, no.

And just be mindful.

I mean, I’m not trying to encourage people

to avoid certain products in particular

but just be mindful of this difference

between modulation and mediation.

And mediating a process through a hardwired

or longstanding biological mechanism

is really where you’re gonna see

the powerful effects over time.

I also, as you’ve probably noticed,

I really tend to favor behavioral tools

and zero cost tools first

and getting those dialed in before you start,

you know, plugging in and swallowing

and, you know, putting things in various places

just to really figure out how your biology works

and explore that,

unless there’s of course a clinical need

to take a prescribed drug,

in which case by all means, listen to your doctor.

Okay, a huge number of people asked me about,

what about light through windows?

And I actually did an Instagram post about this.

Look, setting your circadian clock

with sunlight coming through a window

is gonna take 50 to 100 times longer.

If you want the date on that,

I’d be happy to send you to the various papers

that were described in the previous podcast

that Jamie Zeitzer from Stanford

and I have discussed also elsewhere.

But here’s really the key thing with this.

Do the experiment.

You can download the free app Light Meter.

You can have a bright day outside

or some sunlight, hold up that app, take a picture.

It’ll tell you how many lux.

Now you know what lux are.

It will tell you how many lux are in that environment.

Now close the window.

And if you want, close the screen or don’t open the screen.

You can do all sorts of experiments.

And you’ll see that it will at least half

the amount of lux.

And it doesn’t scale linearly,

meaning let’s say I get 10,000 lux outside,

5,000 looking out through an open window,

and then I close the window and it’s 2,500 lux.

It does not mean that you just need to view that sunlight

for twice as long if it’s half as many lux, okay?

It’s not like 2,500 lux means you need to look

for 10 minutes and 5,000 lux means you look for five minutes.

It doesn’t scale that way just because the biology

doesn’t work that way.

Best thing to do is to get outside if you can.

If you can’t, next best thing to do is to keep

that window open.

It is perfectly fine to wear prescription lenses

and contacts.

Why is it okay to wear prescription lenses and contacts

when those are glass also,

but looking through a window diminishes the effect?

Well, we should think about this.

The lenses that you wear in front of your eyes

by prescription or on your eyes are designed

to focus the light onto your neural retina.

In fact, that’s what nearsightedness is,

is when the image, because your lens doesn’t work

quite right, the image falls in front of the neural retina.

Wearing a particular lens in front of that focuses

the lens onto your retina, onto these very neurons

so they can communicate that to the brain.

Costello is loving this, he’s deep in sleep.

And if we, maybe we could play him some tones

and he’ll remember it later based on the studies

we’re going to talk about in a little bit.

I don’t know how we’d know if he remembered it or not,

but prescription lenses are fine.

In fact, they’re great for this reason.

They’re actually focusing the light onto the retina.

So think about this logically and all of a sudden

it makes perfect sense.

Your glass window or your windshield or the side window

of your car, it isn’t optically perfect to bring the image

and the light onto your retina.

In fact, what it’s doing is it’s scattering

and filtering light, in particular the wavelengths

of light that you want.

So if you live in a low light environment,

lots of questions about this.

We talked about this, the previous podcast,

but just get outside for longer

or and or use really bright lights inside.

Okay, so let’s think about why I’m making some

of these recommendations because I think it can really

empower you with the ability to change your behavior

in terms of light viewing and other things,

depending on time of year,

depending on other lifestyle factors.

The important point to understand is that early in the day,

your central circadian clocks and all these mechanisms

are looking for a lot of light.

I mean, they don’t have a mind of their own,

but it needs a lot of light to trigger this daytime signal,

alertness, et cetera.

And early in the day, but not in the middle of the day,

you can sum or add photons.

So there’s this brief period of time early in the day

when the sun is low in the sky,

when your brain and body are expecting

a morning wake-up signal,

where let’s say it’s not that bright outside.

Someone sent me a picture or a little movie

of their walk in England, and it was pretty overcast

and they were using light meter and they said,

it’s only about 700 lux or maybe even less.

And I said, well, stay outside longer,

but when you get inside, turn on the lights really bright

and overhead lights in particular,

because those will be best for stimulating these mechanisms.

And that’s because at least for the first few hours

of the day, you can continue to sum or add photon activation

of these cells in the eye and the brain.

In the middle of the day, once the sun is overhead,

or even if you stay inside all morning

and then you’re in the circadian dead zone,

which sounds terrible and it is terrible

because it doesn’t matter if you get a ton

of artificial light or even sunlight,

you’re not going to shift your circadian clock,

you’re not going to get that wake-up signal.

And then in the evening,

you want to think about this whole system

as being vulnerable to even a few photons of light

because your sensitivity to light really goes up at night.

And I talked last time about how you can protect

against that sensitivity by looking at the setting sun

and watching the evening sun,

even if it’s not crossing the horizon

around the time of sunset.

And that’s because it adjusts your retinal sensitivity

and your melatonin pathway so that light is not

as detrimental to melatonin at night.

Think about the afternoon sunlight viewing as kind of a,

I think of it as kind of a Netflix inoculation.

It allows me to watch a little bit of Netflix

in the evening, although it’s very hard to watch

a little bit of anything on Netflix.

It seems like there’s some other neurobiological process

going on there where I have to watch episode

after episode after episode.

But in any case, you can protect yourself

against some of that bad effect of light at night

by looking at light in the evening.

It really does adjust down the sensitivity of the system.

Okay, I want to talk about seasonal changes

in all these things as they relate to mood and metabolism.

So depending on where you are in the world,

Northern Hemisphere, Southern Hemisphere,

at the equator or closer to the poles,

the days and nights are going to be different lengths.

That just makes sense.

But that translates to real biological signals

that impact everything from wakefulness and sleep times,

but also mood and metabolism.

So here’s how this works.

Now, after seeing the previous episode of the podcast

and paying attention here, you are armed with the knowledge

to really understand how it is that believe it or not,

every cell in your body is tuned to the movement

of the planet relative to the sun.

So as all of you know,

the earth spins once every 24 hours on its axis.

So part of that day we’re bathed in sunlight,

depending on where we are,

the other half of the day or part of the day

we’re in darkness.

The earth also travels around the sun.

365 days is the time that it takes, one year,

to travel around that sun.

The earth is tilted.

It’s not perfectly upright.

So the earth is tilted on its axis.

So depending on where we are in that 365 day journey,

and depending on where we are in terms of hemisphere,

northern hemisphere, southern hemisphere,

some days of the year are longer than others.

Some are very short, some are very long.

If you’re at the equator,

you experience less variation in day length

and therefore night length.

And if you’re closer to the poles,

you’re going to experience some very long days.

And you’re also going to experience some very short days,

depending on which pole you’re at

and what time of year it is.

A simple way to put this is depending on time of year,

the days are either getting shorter or getting longer.

Now, every cell in your body adjusts its biology

according to day length,

except your brain body and cells

don’t actually know anything about day length.

It only knows night length.

And here’s how it works.

Light inhibits melatonin powerfully.

If days are long and getting longer,

that means melatonin is reduced.

The total amount of melatonin is less

because light is more, therefore melatonin is less.

If days are getting shorter,

light can’t inhibit melatonin as much

through the summing of photon mechanisms

that we talked about before,

and that melatonin signal is getting longer.

So every cell in your body actually knows

external day length and therefore time of year

by way of the duration of the melatonin signal.

And in general, it’s fair to say that in diurnal animals,

meaning animals like us that tend to be awake

during the daytime and not nocturnal animals,

which tend to be awake at night,

the longer the melatonin signal, the more depressed,

not necessarily clinically depressed,

although that can happen,

but the more depressed our systems tend to be.

Reproduction, metabolism, mood,

turnover rates of skin cells and hair cells

all tend to be diminished

compared to the spring and summer months for some,

northern hemisphere spring and summer months,

or the times in which days are very long

and there’s less melatonin that tends to,

in almost all animals, including humans,

more breeding, more hormone elevation

of the hormones that stimulate breeding,

reproduction, and fertility.

Metabolism is up.

Lipid metabolism, fat burning is up.

Protein synthesis is up.

These things tend to correlate with the seasons.

Now, some people are very, very strongly tied

to the seasons.

They get depressed, clinically depressed in winter,

and light therapies are very useful for those people.

Some people love the winter and they’re happiest in winter

and they feel kind of depressed in summer,

although that is far more rare.

That doesn’t mean depression cannot exist in the summer,

but when we’re talking about seasonal depression,

that tends to be true.

It’s more depression in winter.

Now, there’s other things that correlate with seasonality.

Suicide rates tend to be highest in the spring,

not in the winter,

but that has to do with some of the more complicated

and unfortunately tragic aspects of suicide,

which is that oftentimes people will commit suicide

not at the very depths of their energy levels,

but as they’re emerging from those depths of low energy.

So we’ll talk about suicidality and mood disorders

in a later podcast season, meaning a month later,

but for now, just understand that everybody

is going through these natural fluctuations

depending on the duration of the melatonin signal.

Now, this might lead you to say,

well, then I should just really get as much light

as I can all the time and reduce melatonin

and feel great all the time.

Unfortunately, it doesn’t work that way

because melatonin also has important effects

on the immune system.

It has important effects on transmitter systems

in the brain, et cetera.

So everybody needs to figure out for themselves

how much light they need early in the day

and how much light they need to avoid late in the day

in order to optimize their mood and metabolism.

There is no one size fits all prescription

because there is a range of melatonin receptors.

There are a range of everything from metabolic types

to genetic histories, family histories, et cetera.

There is no one size fits all prescription,

but by understanding that light and extended day length

inhibit melatonin and melatonin tends to be associated

with a more depressed or reduced functioning

of these kind of activity driving and mood elevating signals

and understanding that you have some control

over melatonin by way of light,

including sunlight, but also artificial light.

That should empower you, I believe,

to make the adjustments that if you’re feeling low,

you might ask, how much light am I getting?

When am I getting that light?

Because sleep is also important for restoring mood, right?

So you need sleep.

You can’t just crush melatonin across the board

and expect to feel good

because then you’re not going to fall asleep

and stay asleep.

Melatonin, not incidentally, comes from,

is synthesized from serotonin.

Serotonin is a neurotransmitter that is associated

with feelings of wellbeing provided to proper levels,

but wellbeing of a particular kind,

wellbeing associated with quiescence and calm

and the feeling that we have enough resources

in our immediate kind of conditions.

It’s the kind of thing that comes from a good meal

or sitting down with friends or holding a loved one

or conversing with somebody that you really bond with.

Serotonin does not stimulate action.

It tends to stimulate stillness.

Very different than the neuromodulator dopamine,

which is a reward, feel-good neuromodulator

that stimulates action.

And actually dopamine is the precursor to epinephrine,

to adrenaline, which actually puts us into action.

It’s actually made from dopamine, right?

So you can start to think about light as a signal

that is very powerful for modulating things

like sleep and wakefulness,

but also serotonin levels, melatonin levels.

And I talked about this previously,

but I’ll mention once more

that light in the middle of the night

reduces dopamine levels to the point

where it can start causing problems

with learning and memory and mood.

That’s one powerful reason to avoid bright light

in the middle of the night.


Seasonal rhythms have a number of effects,

but humans are not purely seasonal breeders.

Unlike a lot of animals, we breed all year long.

In fact, there’s a preponderance

of September babies in my life.

Not actual babies, people that are born in September,

which means that they were conceived in December.

Without knowing the details, we can fairly assume that.

And December, at least in the Northern hemisphere,

days tend to be shorter and nights tend to be longer.

So clearly humans aren’t seasonal breeders,

but there are shifts in breeding and fertility

that exist in humans,

but also much more strongly in other animals.

So seasonal effects vary.

Some of you will experience very strong seasonal effects.

Others of you will not.

I think everybody should be taking care

to get adequate sunlight and to avoid bright light at night

throughout the year, if possible.

Throughout this podcast and in previous episodes,

I’ve been mentioning neuromodulators,

things like serotonin and dopamine,

which tend to bias certain brain circuits

and things in our body to happen

and certain brain circuits and things in our body

not to happen.

One of the ones I’ve mentioned numerous times

is epinephrine, which is a neuromodulator

that tends to put us into action, make us want to move.

In fact, when it’s released in high amounts

in our brain and body, it can lead to what we call stress

or the feeling of being stressed.

Several people ask me,

what’s the difference between epinephrine and adrenaline?

Adrenaline is secreted from the adrenal glands,

which sit right above our kidneys.

Epinephrine is the exact same molecule

except that it’s released within the brain.

And so people use these phrases

or these words rather interchangeably.

Epi means near or on top of sometimes

and neph, neph, anytime you see nephron or eph,

it means kidney.

So it means near the kidney.

So epinephrine actually means near the kidney.

So it was used originally to describe adrenaline,

but epinephrine and adrenaline are basically the same thing

and they tend to stimulate agitation

and the desire to move.

That’s what that’s about.

Which brings us to the topic of exercise.

Got a lot of questions about exercise.

What forms of exercise are best for sleeping well?

When should I exercise, et cetera?

There’s a lot of individual variability around this,

but I can talk about what I know from the science literature

and what I happen to do myself.

There are basically two forms of exercise

that we can talk about.

Although, of course,

I realize there are many different forms of exercise.

There’s much more nuance to this,

but we can talk about cardiovascular exercise

where the idea is to repeat a movement

over and over and over continuously.

So that’d be like running, biking, rowing, cycling,

this kind of thing.

Or there’s a resistance exercise where you’re moving,

lifting, presumably putting down also,

things of progressively heavier and heavier weight

that you couldn’t do continuously for 30 minutes.

So cardiovascular exercise

is typically the more aerobic type exercise

and resistance exercise, of course,

is the more anaerobic type exercise.

And yes, there’s variation between the two.

Most studies of exercise have looked at aerobic exercise

because that’s basically the thing

that you can get a rat or a mouse to do.

You know what’s really weird about rats and mice?

They like to run on wheels so much

that someone actually did this study.

It was published in Science.

They put a wheel, a running wheel,

in the middle of a field and mice ran to that wheel

and ran on the wheel.

They, turns out that what they like

is the passage of the visual image of the bars

in front of their face,

which I find kind of remarkable and troubling

because it seems so like trivial.

But anyway, they love aerobic exercise.

And so most of the studies were done on these mice

that love running on wheels.

Whereas so far, it’s been challenging to find conditions

in which mice really like to lift weights

or will do it in a laboratory.

So any weight-bearing exercise studies

really have to be done in humans.

And since humans are what we’re interested in,

there are some studies looking at these two things

and when they tend to work best.

Now you will see some places aerobic exercise

is best done in the morning

and weight training is best done in the afternoon.

I think there’s far more individual variation than that.

I think there are, however, a couple of windows

that the exercise science literature

and the circadian literature points to

as windows related to body temperature

in which performance is optimized,

injury is reduced, and so on.

And those tend to be 30 minutes after waking.

And that probably correlates with the inflection

in cortisol associated with waking,

whether or not you’ve gotten light or not.

Three hours after waking,

which probably correlates to the rise in body temperature,

sometime right around waking.

And the later afternoon, usually 11 hours after waking,

which is when temperature tends to peak.

So some people like to exercise in the morning.

Some people like to exercise in the afternoon.

It really depends.

I think for those of us with very busy schedules,

it’s advantageous to be able to do your training

whenever you have the opportunity to do it,

unless you can really control your schedule.

And so I would never want these recommendations

to seem like recommendations.

What I’m really describing is some opportunities

30 minutes after waking, three hours after waking,

or 11 hours after waking has been shown,

at least in some studies, to optimize performance,

reduce injury, and that sort of thing.

But you really have to figure out what works for you.

A note about working out first thing in the morning.

Last time we talked about non-photic phase shifts.

If you exercise first thing in the morning,

your body will start to develop an anticipatory circuit.

There’s actually plasticity in these circadian circuits

that will lead you to want to wake up

at the particular time that you exercised

the previous three or four days.

So that can be a powerful tool,

but you still want to get light exposure

because it turns out that light and exercise converge

to give an even bigger wake-up signal to the brain and body.

So you might want to think about that.

Some people find if they exercise late in the day,

they have trouble sleeping.

In general, intense exercise does that,

whereas the kind of lower intensity exercise doesn’t.

I found some interesting literature

that talked about sleep need and exercise.

I found this fascinating that if one is waking,

not feeling rested and recovered from,

and yet sleeping the same amount that they typically have,

it’s quite possible that the intensity of exercise

in the preceding two or three days is too high.

Whereas if one can’t recover

no matter how much sleep they get,

they’re just sleepy all the time,

I realize these things are correlated,

that the volume of training might be too high.

Now, I’m not an exercise scientist.

We should probably get Andy Galpin or somebody else on here

who’s really an expert in this kind of stuff.

I do realize as soon as anyone talks about exercise

or nutrition publicly,

they’re basically opening themselves up

to all sorts of challenges

because you can basically find support

for almost any protocol in the literature.

What I’ve looked at was two journals in particular,

International Journal of Chronobiology

and Journal of Biological Rhythms, excuse me,

to assess these parameters

that I mentioned just a moment ago,

because the studies tended to be done in humans.

They were fairly recent and they came from groups

that I recognized as well as knowing

that those journals are peer reviewed.

Many of your questions were about neural plasticity,

which is the brain and nervous system’s ability to change

in response to experience.

There was a question that asked whether or not

these really deep biological mechanisms

around wakefulness, time of waking, sleep, et cetera,

were subject to neural plasticity, and indeed they are.

Some of that plasticity is short-term

and some of it is more long-term.

There’s a really good analogy here,

which is if you happen to eat on a very tight schedule

where every day, say at 8 a.m., noon, and 7 p.m.

is when you eat your food, not suggesting you do this,

but let’s say you were to do that for a couple days.

After a few days, you would start to anticipate

those mealtimes where no matter where you were in the world,

no matter what was going on in your life,

about five to 10 minutes before those mealtimes,

you would start to feel hungry and even a little agitated,

which is your body’s way of trying to get you

to forage for food.

And that’s because of some peptide signals

that come from the periphery from your body,

things like hypocretinorexin,

that signal to the hypothalamus and brainstem

to make you active and alert and look for food

and feel hungry.

So there’s kind of an anticipatory circuit

that’s a chemical circuit, but eventually over time,

the neurons, the neural circuits

that control hypocretinorexin would get tuned

to the neural circuits that are involved in eating

and maybe even smell and taste

to create a kind of eating circuit

that’s unique to your pattern, to your rhythms.

The same thing is true for these waking and exercise

and other schedules, including ultradian schedules.

If you wake up in the morning

and start getting your sunlight,

you start exercising in the morning

or you exercise in the afternoon,

pretty soon your body will start to anticipate that

and start to secrete hormones and other signals

that prepare your body for the ensuing activity

of waking up or going to sleep.

So if you get onto a pattern or a rhythm,

even if that rhythm isn’t down to the minute,

you’ll find that there’s plasticity in these circuits

and it becomes easier to wake up early if that’s your thing

or exercise at a particular day if that’s your thing.

That’s the beauty of neural plasticity.

A number of people ask what can I do to increase plasticity?

And that really comes in two forms.

There’s plasticity that we can access in sleep

to improve rates of learning and depth of learning

from the previous day or so.

And there’s this NSDR, non-sleep deep rest

that can be done without sleeping

to improve rates of learning and depth of retention,

et cetera.

So let’s consider those both

and you can incorporate these protocols if you like.

Again, these are based on quality peer-reviewed studies.

First, let’s talk about learning in sleep.

This is based on some work

that I’ll provide the reference for

that was published in the journal Science.

Excellent journal.

Matt Walker also talks about some of these studies

done by others in his book, Why We Sleep.

The studies, just to remind you,

are structured the following way.

An individual is brought into a laboratory,

does a spatial memory task.

So there tends to be a screen

with a bunch of different objects

popping up on the screen in different locations.

So it might be a bulldog’s face,

there might be a cat, then it might be an apple,

then it might be a pen in different locations.

And that sounds trivially easy,

but with time you can imagine it gets pretty tough

to come back a day later and remember

if something presented in a given location

was something you’ve seen before

and whether or not it was presented in that location

or a different location.

If you had enough objects and changed the locations enough,

this can actually be quite difficult.

In this study, the subjects

either just went through the experiment

or a particular odor was released into the room

while they were learning

or a tone was played in the room while they were learning.

And then during the sleep of those subjects

the following night and the following night,

this was done repeatedly for several nights,

the same odor or tone was played

while the subjects were sleeping.

They did this in different stages of sleep,

non-REM sleep and rapid eye movement sleep, REM sleep.

They did this with just the tone in sleep

if the subjects had the odor, but not the tone.

They did it with putting the tone

if they had had the odor while learning.

So basically all the controls,

all the things you’d want to see done

to make sure that it wasn’t some indirect effect,

some modulatory effect, okay?

And what they found was that providing the same stimulus,

the odor if they smelled an odor or a tone

if the subjects heard a tone while learning,

if they just delivered that odor or tone

while the subjects slept,

rates of learning and retention of information

was significantly greater.

This is pretty cool.

What this means that you can cue the subconscious brain,

the asleep brain to learn particular things better

and faster.

So how might you implement this?

Well, you could play with this if you want.

I don’t see any real challenge to this

provided the odor is a safe one

and it doesn’t wake you up

and the tone is a safe one and doesn’t wake you up.

You could do this by having a metronome, for instance,

while learning something,

playing in the background or particular music,

and then have that very faintly while you sleep.

So you could apply this if you like and try this.

There are a number of groups I think now

that are trying this using tactile stimulation.

So slight vibration on the wrist during learning

and then the same vibration on the wrist during sleep.

It does not appear that the sensory modality,

whether or not it’s odor or auditory tone

or tactile stimulation, somatosensory stimulation,

whether or not it matters.

It’s remarkable because it really shows

that sleep is an extension of the waking state.

We’ve known that for a long time,

but this really tethers those two

in a very meaningful and actionable way.

So I’ll report back to you

as I learn more about these studies,

but that’s what I know about them at this point.

As long as we’re there,

we might as well talk about dreaming

because I got so many questions about dreams.

A couple of you want to ask me what their dreams meant.

Look, I don’t even know what my dreams mean half the time.

I occasionally will wake up from a dream and remember it.

If you want to remember your dreams better,

if you’re somebody who has challenges

remembering your dreams,

you can set your alarm so that you wake up

in the middle of one of these 90 minute cycles,

which toward morning tend to be occupied

almost exclusively by REM sleep.

Remember early in the night,

you have less REM sleep than later in the night,

but you want to get as much sleep as you can

because that’s healthy.

So I don’t know that you want to wake yourself up.

Some people find that writing down their thoughts

immediately first thing in the morning

allows them to later spontaneously

remember their dream they had.

There’s some literature on that.

The meaning of dreams is a little bit controversial.

Some people believe they have strong meaning.

Other people believe that they can be

just spontaneous firing of neurons

that were active in the waking state

and don’t have any meaning.

There are good data to show

that when you learn new spatial environments,

that there’s a replay of those environments,

so-called place cells that fire in your brain

only when you enter a particular environment,

that those are replayed in sleep

in almost direct fashion to the way that

things were activated

when you were learning that spatial task.

Dreams are fascinating.

We’re paralyzed during dreams,

which brings us to another question.

Somebody asked about sleep paralysis.

We are paralyzed for much of our sleep, so-called atonia,

presumably so we don’t act out our dreams.

Some people wake up and they’re still paralyzed.

I’ve actually had this happen to me,

not very many times, but a few times,

and then they jolt themselves awake.

And it actually is quite terrifying,

I can say from personal experience,

to wake up, be wide awake,

and you cannot move your body at all.

It’s really quite frightening.

There are a couple of things that will increase

the intrusion of atonia into the wakeful state,

which is essentially means you’re waking up,

but you can’t move.

One is marijuana, THC.

I’m not a marijuana smoker.

I’m not a cop, or I don’t know the legality where you live,

so I’m not saying one thing or another about marijuana.

I’m just, the fact that I had that experience

without marijuana means that it can happen regardless.

But marijuana smokers, for whatever reason,

maybe it has something to do with the cannabinoid receptors

or the serotonin receptors

downstream of the motor pathways.

I don’t know.

I couldn’t find any literature on this,

but marijuana smokers report higher frequency

of this kind of paralysis and wakefulness

as you transition from sleep to wakefulness.

I suppose probably one could learn

to get comfortable with it.

For me, it was terrifying,

because I’m just used to being able

to move my limbs, fortunately,

and I wasn’t able to,

and it’s quite a thing, let me tell you.

Okay, some other questions about neuroplasticity.

So the other form of neuroplasticity

is not the neuroplasticity that you’re amplifying

by listening to tones or smelling odors in sleep,

but the neuroplasticity that you can access

with non-sleep deep rest.

So NSDR, non-sleep deep rest,

as well as short 20-minute naps,

which are very close to non-sleep deep rest,

because people rarely drop into deep states of sleep

during short naps, unless they’re very sleep-deprived.

NSDR has been shown to increase rates of learning

when done for 20-minute bouts

to match an approximately 90-minute bout of learning.

So what am I talking about?

90-minute cycles are these ultradian cycles

that I’ve talked about previously,

and we tend to learn very well

by taking a 90-minute cycle,

transitioning into some focus mode early in the cycle

when it’s hard to focus,

and then deep focus and learning

feels almost like agitation and strain,

and then by the end of that 90-minute cycle,

it becomes very hard to maintain focus

and learn more information.

There’s a study published in Cell Reports last year,

great journal, excellent paper,

showing that 20-minute naps or light sleep

of the sort of non-sleep deep rest

taken immediately after or close to,

it doesn’t have to be immediately

after you finish the last sentence of learning

or whatever it is or bar of music,

but a couple minutes after transitioning

to a period of non-sleep deep rest

where you’re turning off the analysis

of duration, path, and outcome

has been shown to accelerate learning

to a significant degree,

both the amount of information

and the retention of that information.

So that’s pretty cool because this is a cost-free,

drug-free way of accelerating learning

without having to get more sleep,

but simply by introducing these 20-minute bouts.

I would encourage people if they want to try this

to consider the 20 minutes per every 90 minutes

of ultradian learning cycle.

There, you’re incorporating a number

of different neuroscience-backed tools,

90-minute cycles for focused learning.

It could be motor, it could be cognitive,

could be musical, whatever,

and then transition to a 20-minute

non-sleep deep rest protocol.

Just want to cue you to the fact that in last episode

in the caption on YouTube,

we provided links to two different yoga nidra

non-sleep deep rest protocols,

as well as hypnosis protocols that are clinically backed

from my colleague, David Spiegel

at Stanford’s psychiatry department.

All those resources are free.

There are also a lot of other hypnosis scripts out there.

I like the ones from Michael Sealy, S-E-A-L.

I think it’s E-Y, although maybe it’s just L-Y.

You can find them easily on YouTube,

clinical hypnosis scripts, meaning not stage hypnosis.

They’re not designed to get you to do anything.

In fact, they’re just designed

to help rewire your brain circuitry.

Now, how does hypnosis work that way?

This has a lot to do with sleep

because it engages neuroplasticity

by bringing together two things

that normally are separate from one another.

One is the alert, focused, wakeful state

where you activate the learning,

and then there’s the deep rest

where the actual reconfiguration of the neurons

and synapses takes place.

Hypnosis brings both the focus

and the deep rest component into the same

compartment of time.

It’s a very unique state in that way.

So hypnosis kind of maximizes the learning bout

and the non-sleep deep rest bout and combines them.

But of course, that requires some guidance

from a script or from a hypnotist,

clinically trained hypnotist,

and it becomes hard to acquire detailed information.

It’s more about shifts in state,

like fear to states of calm

or quitting smoking,

anxiety around a trauma to release of anxiety

around a trauma,

rather than specific information learned in hypnosis, okay?

So hypnosis seems more about modulating the circuits

that underlie state as opposed to specific information.

Although I would not be surprised

if there weren’t certain forms of hypnosis

that could increase retention

and learning of specific information,

but I’m not aware of any of those protocols out there yet,

which brings us to the next thing

about learning and plasticity,

which is nootropics, AKA smart drugs.

This is a big topic.

That sigh was a sigh of concern

about how to address nootropics in a thorough enough,

but thoughtful enough way.

Look, I have a lot of thoughts about nootropics.

First of all, it means smart drugs, I believe.

And I don’t like that phrase

because let’s just take a step back

and think about exercise.

You just say, I want to be more physically fit.

What does that mean?

Does it mean, I would ask for more specificity.

I’d say, do you want to be stronger?

Okay, maybe you need to lift heavier objects progressively.

Do you want more endurance?

Very different protocol to access endurance.

Do you want flexibility?

Do you want explosiveness or suppleness?

Huge range of things that we call physical fitness.

Maybe you want all of those.

If we were talking about emotional fitness,

we would say, well, an ability to feel empathy,

but probably also to disengage from empathy

because you don’t want to be tethered

to other people’s emotions all the time.

That’s not healthy either.

You would think about being able to access

a range of emotions, but for some people,

their range into the sadness regime is really quite vast,

but their range into the happiness regime

might be kind of limited.

For other people who are in a manic state,

it might be they can access all the happy stuff,

but not the sadder stuff.

So I’m speaking by way of analogy here,

but if we say, we’re talking about cognitive abilities,

we have to ask, okay, creativity, memory.

We tend to associate intelligence with memory.

I think this goes back to like spelling bees or something,

the ability to retain a lot of information

and just regurgitate information,

which will get you some distance in some disciplines of life,

but it won’t allow you creative thinking.

It’s necessary for creative thinking.

You need a knowledge base, right?

You can’t just look up everything on Google

despite what certain educators or so-called educators say.

You need a database so that you could have

the raw materials with which to be creative.

So necessary to have memory,

but not sufficient to be creative, right?

The creative could have a poor memory for certain things,

but certainly not for everything.

They can’t have interrogate and retrograde amnesia.

They’d be like the goldfish

that every time around the tank,

it can’t remember where it’s at.

I actually don’t know that they’ve ever done

that experiment by the way,

but so no disrespect to goldfish, but you know.

So you get the idea, you’ve got creativity,

you have memory, you have the ability to task switch, right?

You have the ability to strategy develop

and strategy implement.

So the problem I have with the concept of a nootropic

or a smart drug is it’s not specific

as to what cognitive algorithm you’re trying to engage.

We need more specificity.

That said, there are elements to learning

that we’ve discussed here before that are very concrete.

Things like the ability to focus and put the blinders

onto everything else that’s happening around you

and in your head mainly, right?

Distractions about things you should be doing,

could be doing, or might be doing

and focus on what you need to do.

And then that’s required for triggering

that acetylcholine neuromodulator

that will then allow you to highlight

the particular synapses that will then later change

in sleep.

So nootropic allows you to bypass the need

for sleep and deep rest.

That’s important to understand.

So I daydream about a day

when people will be able to access compounds that are safe,

that will allow them to learn better,

meaning to access information, focus better,

as well as to sleep better and activate the plasticity

from the learning bout.

Right now, most nootropics tend to bundle

a bunch of things together.

Most of them include some form of stimulant, caffeine.

Episode two, I tell you more probably

than you ever wanted to know about caffeine,

adenosine and how that works.

So refer there for how caffeine works.

But stimulants will allow you to increase focus

up to a particular point.

If you have too little alertness in your system,

you can’t focus too much.

However, you start to cliff and focus drifts, okay?

So you can’t just ingest more stimulant to be more focused.

It doesn’t work that way.

Most nootropics also include things that increase

or are designed to increase acetylcholine,

things like alpha-GPC and other things of that sort.

And indeed, there’s some evidence

that they can increase acetylcholine.

I refer you again to, the website,

to evaluate any supplements or compounds for their safety

and their effects in humans and animals.

Free website, as well as with links to studies.

So we need the focus component.

We need the alertness component.

The alertness component comes from epinephrine,

traditionally from caffeine stimulation.

The acetylcholine stimulation traditionally comes

from choline donors or alpha-GPC, things of that sort.

And then you would want to have some sort of off switch

because anything that’s going to really stimulate

your alertness that then provides a crash,

that crash is not a crash into the deep kind

of restful slumber that you would want for learning.

It’s a crash into the kind of,

let’s just call it lopsided sleep,

meaning it’s deep sleep, but it lacks certain spindles

and other elements of the physiology, sleep spindles,

that really engage the learning process

and the reconfiguration of synapses.

So right now, my stance on nootropics

is that maybe, maybe for occasional use,

provided it’s safe for you, I’m not recommending it,

but in general, it tends to use more of a shotgun approach

than is probably going to be useful

for learning and memory in the long run.

A lot of people ask about modafinil or armodafinil,

which was designed for treatment of narcolepsy.

So right there, it tells you it’s a stimulant.

And yes, there is evidence

it will improve learning and memory.

Modafinil is very expensive.

Last time I checked, armodafinil, I think,

is the recent released generic version of this

that’s far less expensive.

Most of these things look a lot like amphetamine,

and many of them have the potential for addiction

or it can be habit-forming, but more importantly,

a lot of those things also can create metabolic effects

by disruption to insulin receptors and so forth.

So you want to approach those

with a strong sense of caution.

Now, there are the milder things that act as nootropics.

I mentioned some of them, like alpha-GPC.

Some people like ginkgo.

Ginkgo gives me vicious headaches, so I don’t take it.

So, you know, people really differ.

Last podcast, I recommended magnesium threonate

if you were exploring supplements.

I’m not recommending anything directly.

I’m just saying if you’re exploring supplements,

magnesium threonate seems, among the magnesiums,

to be one of the more bioavailable and useful for sleep.

I recommended it actually to a good friend of mine.

It gave him, at very low dose, he had stomach issues with it.

He just had to simply stop taking it.

So there’s variability there.

It gave him some stomach cramping

and just didn’t feel good on it.

Stopped it, he felt better.

Other people take magnesium threonate and feel great.

I was asked, do magnesium need to be taken

with or without food, daytime or before sleep?

If you’re going to go that route,

it should be taken 30 to 60 minutes before sleep

because it’s designed to make you sleepy.

And I’m not aware that it has to be taken with food,

but again, all of this has to be run by your doctor

and this is your healthcare to govern.

These are not strict recommendations, so look into it.

But magnesium threonate,

most people I’ve recommended it to

have benefit from it tremendously.

Some people can’t tolerate it, so you have to find out.

There were a number of questions about other supplements

designed to access deep sleep,

in part to access neuroplasticity,

but now I’m just sort of transitioning

from neuroplasticity to these compounds

that can regulate sleep.

One of them that I discussed at the end of the last podcast,

I got a lot of questions about is apigenin, A-P-I-G-E-N-I-N.

Apigenin, if you look in the literature,

the way it works is it increases some of the enzymes

associated with GABA metabolism.

It actually, GABA is an inhibitory neurotransmitter.

It’s the neurotransmitter that is increased

after a couple drinks containing alcohol

and that shut down the forebrain.

Apigenin is a derivative of the chamomile.

I think that the proper pronunciation of this

is matricaria chamomila,

although I always feel like I should be using

a Spanish accent whenever I say something like that.

Other related things that impact the GABA system

and increase GABA are things like passion flower,

which is passiflora incurata.

I don’t know why the Italian, is that Italian?

Anyway, my Italian colleagues, please forgive me.

I have some very close Italian friends

and colleagues in Genoa.

I butchered the Italian, sorry.

In any event, apigenin and passion flower

found in a lot of supplements

designed to increase sleepiness and sleep

and they work presumably because they increase GABA.

Actually, they work on chloride channels

rather than give you a whole lecture

on membrane biophysics and neurons.

I’ll just say that when neurons are really active,

it’s because sodium ions, salt,

rushes into the cells and causes them to fire electrically.

The cells tend to become less active as more chloride,

which is a negatively charged ion.

This is probably taking some of you back

to either the wonderful times or traumas

of high school physics.

The chloride is negatively charged,

so it tends to make cells less electrically positive

because it carries a negative charge

and hyperpolarizes the neuron.

So apigenin works through these,

increasing the activity of these chloride channels.

Passion flower works by increasing

the activity of these chloride channels

and GABA transmission.

It tends to increase this inhibitory neurotransmitter

that shuts off our thinking,

our analysis of duration, path, and outcome.

So if you’re going to explore these things,

I suggest you at least know how they work.

You at least go to,

that you talk to your doctor about them.

Some people asked about serotonin

for getting to sleep and staying asleep.

Now, I understand the rationale here,

just like I understand the rationale

of taking something like mucunipurines or L-DOPA

to increase dopamine.

But sometimes what works on paper

doesn’t really work in the real world.

I personally have tried taking a supplement,

which was L-tryptophan,

which is the precursor to serotonin,

or 5-HTP, which is designed to increase.

It is serotonin, basically.

You’re just one biochemical step away

from taking actual serotonin.

And I’ll be honest,

the sleep that I had with increased serotonin

by way of tryptophan or 5-HTP was dreadful.

I fell asleep almost immediately.

You say, well, that’s great.

And 90 minutes later, I woke up

and I couldn’t sleep almost for 48 hours.

Now, that was me.

I have a pretty sensitive system to certain things

and not to other things.

Some people love these things.

So you really have to be thoughtful and explore them

with that kind of awareness of being thoughtful

and realizing that what works for you

might not work for everybody

and what works for everybody might not work for you.

Okay, I’d like to continue

by talking about the role of temperature

in sleep, accessing sleep, staying asleep, and wakefulness.

But first I want to tell a joke

because I think this joke really captures

some of the critical things to understand

about any self-experimentation that you might do.

So this is a story that was told to me

by a colleague of mine who’s now a professor of Caltech,

not to be named.

So there’s a scientist and they’re in their lab

and they’re trying to understand

how the nervous system works.

So they go over to a tank and they pick up a frog

and they take the frog and they put it down on the table

and they clap and the frog jumps.

So they think for a while and they pick up the frog.


They go over to the cabinet

and they take out a little bit of a paralytic drug

and they inject it locally into the back leg,

set it down and clap and the frog jumps,

but it kind of like jumps to the side a little bit.

Mm-hmm, they pick it up.

They inject the paralytic into the other back leg.

They clap again.

The frog jumps, but it really doesn’t jump well that time.

It kind of drags itself forward.

So they pick it up and they inject the paralytic

into the remaining two legs.

They set it down and they clap and the frog doesn’t jump.

They go, oh my goodness.

The legs are used for hearing.

Now they publish the paper.

Paper comes out in a great journal, news releases.

It’s really big deal.

Their career takes off.

20 years later, a really smart graduate student

comes along and says, yeah, but that’s loss of function.

Doesn’t really show gain of function.

So let’s take a closer look.

So they repeat the first experiment and it checks out.

Everything happens the same way.

But then they take the frog

and they inject a drug into all four legs

that turns off the paralytic, right?

It’s an antagonist.

They set the frog down, they clap and the frog jumps.

They go, oh my goodness, it’s true.

The legs really are for hearing.

Now, first of all, I want to make the point

that this is not to illustrate

that science is not a good practice.

It is.

We need to do loss of function

and gain in function experiments.

But just to show that correlation

and causation is complicated,

you need to do a variety of control experiments

and you really need to figure out what works for you.

And so while science can provide answers

about what works under very controlled conditions,

it doesn’t and can never address all the situations

in which a given compound, a given practice

will or won’t work.

And it’s not just individual variability.

It’s that there are a number of different factors.

You all of course know that light can activate

and shift your circadian rhythm,

but so can exercise, so can food.

The last point I want to make is an important one,

which is that no frogs were hurt

in the telling of this joke.

Okay, so let’s continue.

I want to talk about temperature.

Temperature is super interesting

as it relates to circadian rhythms

and wakefulness and sleep.

First, let’s take a look at what’s happening

to our body temperature across each 24-hour cycle.

In general, our temperature tends to be lowest

right around 4 a.m. and starts creeping up

around 6 a.m., 8 a.m. and peaks sometime

between 4 p.m. and 6 p.m.

Now, that varies from person to person,

but in general, if we were to continuously monitor

or occasionally monitor temperature,

that’s what we would see.

Now, what’s interesting is that even in the absence

of any light cues or meal cues, we would have a shift.

We would have an oscillation or a rhythm

in our temperature that would go from high to low.

This is why the idea that we’re all 96.8

and that’s our correct temperature, forget that.

That is no longer true.

It never was true.

It depends on what time of day you measure temperature.

However, there is a range, which is within normal range.

I think most of us associate fever

with somewhere around 100, 101, 103.

That’s concerning.

And we will be very concerned

if temperature dropped too low as well.

The way that the temperature rhythm that’s endogenous,

that’s within us and rhythmic no matter what,

the way it gets anchored to the pattern I described before

of being lowest at 4 a.m. and increasing again

around through the day until about 4 to 6 p.m.

is by way of entrainment or matching to some external cue,

which is almost always going to be light, but also exercise.

Now, you may have experienced this temperature rhythm

and how quickly it can become unentrained

or it can fall out of entrainment.

Here’s an experiment I wouldn’t want you to do,

but you’ve probably experienced this before,

where you wake up, it’s sunny outside,

and maybe you have some email or some things to take care of,

or maybe you didn’t sleep that well the night before,

and so you stay indoors.

You don’t change anything about your breakfast.

You don’t change anything

about your within home temperature or anything like that.

And somewhere right around 10 or 11 o’clock,

you start feeling kind of chilled, like you’re cold.

Well, what happened was the oscillators,

the clocks in your various tissues

that are governed by temperature and circadian rhythm

are starting to split away

from your central clock mechanisms.

So it’s actually important

that your temperature match day length.

Now, there’s another way in which temperature matches,

or daytime, excuse me.

There’s also an important way

in which temperature matches day length.

In general, as days get longer, it tends to be hotter out.

Not always, but in general, that’s the way it is.

And as days get shorter, it tends to be colder outside.

So temperature and day length are also linked,

metabolically they’re linked,

biologically they’re linked, excuse me,

and atmospherically they’re linked

for the reasons that we talked about before

about duration of day length

and other climate features and so forth.

So one of the most powerful things

about setting your circadian rhythm properly

is that your temperature will start to fall

into a regular rhythm.

And that temperature has a very strong effect

on things like metabolism

and when you will feel most willing

and interested in exercising.

Typically, the willingness to exercise and engage

in any kind of activity, mental or physical,

is going to be when that rise in temperature is steepest,

when the slope of that line is greatest.

That’s why 30 minutes after waking

is one of those key windows,

as well as three hours after waking,

and then when temperature actually peaks,

which is generally, generally,

about 11 hours after waking.

So this is why we say that temperature

and circadian rhythm are linked,

but they’re actually even more linked than that.

We’ve talked before about how light enters the eye,

triggers activation of these melanopsin cells,

which then triggers activation

of the suprachiasmatic nucleus,

the master circadian clock.

And then I always say the master circadian clock

informs all the cells and tissues of your body

and puts them into a nice cohesive rhythm.

But what I’ve never answered

was how it actually puts them into that rhythm.

And it does it two ways.

One is it secretes a peptide.

A peptide is just a little protein

that floats through the bloodstream

and signals to the cells,

okay, we’re tuning your clock,

kind of like a little, you know, in a watch store,

the watch store owner would tune the clocks.

But the other way is it synchronizes the temperature

under which those cells exist.

So temperature is actually the effector

of the circadian rhythm.

Now, this is really important

because changes in temperature by way of exercise,

by way of eating, but especially by way of exercise

can start to shift our circadian rhythm pretty dramatically.

But let’s even go to a more extreme example.

Nowadays, there’s some interest in cold showers

and ice baths.

Not everybody is doing this, I realize.

People seem to either love this or hate this.

I don’t mind the cold dunk thing.

I get regular about this from time to time and I’ll do it.

I haven’t been doing it recently.

It’s always painful to do the first couple of times

and then you get kind of used to it.

However, I’ve taken people to a cold dunk or an ice bath.

I have a family member

who wouldn’t get in literally past her toes.

She was like, this is just too aversive for me.

Some people really like the cold, people very tremendously.

Getting into an ice bath is very interesting

because you have a rebound increase in thermogenesis.

Now you should know from the previous episode

that as that temperature increases,

it will shift your circadian rhythm

and which direction it shifts your circadian rhythm

will depend on whether or not you’re doing it

during the daytime or late in the day.

If you do it after 8 p.m.,

it’s going to make your day longer, right?

Because your body and your central clocks

are used to temperature going up early in the day

and throughout the day and peaking in the afternoon.

If you then increase that further

or you simply increase it over its baseline at 8 p.m.

after temperature was already falling,

even if it’s just by a half a degree or a couple of degrees

or you do that with exercise,

doesn’t have to be with the ice bath,

you are extending, you are shifting forward.

You’re phase delaying your clock.

You’re convincing your clock

and therefore the rest of your body

that the day is still going, right?

You’re giving it the perception,

the cellular and physiological perception

that the day is getting longer

and you will want to naturally stay up later

and wake up later.

Now you might say, wait, I do an ice bath late at night

and I feel great and I fall deeply asleep.

Well, cold can trigger the release of melatonin.

There’s a rebound increase in melatonin.

So that could be the cause of that effect.

You have to see what works for you.

But if you do the ice bath early in the day

and then get out, you will experience a more rapid rise

or cold shower early in the day,

a more rapid rise in your body temperature

that will phase advance your clock

and make it easier to get up early the following day.

So for those of you that are having trouble getting up,

and this is going to almost sound laughable,

but a cold shower first thing in the morning

will wake you up,

but that’s waking you up in the short term

because of a different mechanism,

which I’ll talk about in a moment,

but it also is shifting your clock.

It’s phase advancing your clock

in a way that makes you more likely

to get up earlier the next day, okay?

So in other words, increasing your temperature

by getting in an ice bath or cold shower,

or exercising, which causes a compensatory increase

in body temperature.

Think about the normal pattern of body temperature,

low around 4.35 AM, starts to peak right around waking,

excuse me, starts to increase right around waking,

then steep slope, steep slope to a peak

around four to 6 PM and then drops off.

If you introduce an increase in body temperature

by way of cold exposure early in the day,

let’s say 6 AM or 5 AM,

if you’re masochistic enough to get into a cold shower

at that time, more power to you,

it’s going to make you want to wake up

about half hour to an hour earlier the next day

than you normally would.

Whereas if you do it while your temperature is falling,

it will tend to delay and make your body perceive

as if the day is getting longer.

These are phase advances and phase delays.

We’re going to get into this in far more detail

when we talk about jet lag and shift work in episode four,

as well as other things.

But temperature is, again,

it’s not just one tool to manipulate wake up time

and circadian rhythm and metabolism.

It is the effector.

It is the way that the central circadian clock

impacts all the cells and tissues of your body.

If you want to read further about this,

and you’re really curious about the role of temperature,

work by Joe Takahashi,

who used to be at Northwestern University

and is now at UT Southwestern in Dallas,

incredible scientist,

and has really worked out a lot of the mechanisms

around temperature and circadian rhythms.

You can just Google his name

and you’ll see a whole bunch of studies there.

I want to talk about cold and cold exposure

because there’s a great misconception about this

that actually you can leverage once you understand

how to use cold to either increase thermogenesis

and fat loss metabolism,

or you can use it for stress mitigation and mood.

And it really depends on one simple feature

of how you approach the ice bath or cold shower.

If you get into an ice bath or cold shower

and you are calming yourself,

you’re actively calming the autonomic nervous system,

maybe through some deep breathing,

maybe through visualization,

maybe you sing a song, you know, people do this stuff.

They use various tools.

Some people find paying attention

to an external stimulus is more helpful.

You know, thinking about something

not the experience of the cold.

Other people find that directly experiencing the cold

in its most intense form

and kind of going into the cold, quote unquote,

is the best way to approach it.

It really varies for people.

There’s no right or wrong way to go about this.

But the goal of using cold exposure for stress inoculation

and to raise your stress threshold

to be able to tolerate heightened levels

of real life stress, not the ice bath,

but real life stress like work stress

and relational stress, et cetera,

is by suppressing the activation

of the so-called sympathetic nervous system,

meaning the alertness or stress system.

That involves buffering

or trying to resist the shiver response.

The shiver response is an autonomic response

designed to generate heat, presumably,

and actually that is what it does,

in order to counter the cold.

So when you use cold exposure

and you’re kind of muscling through it

or you’re learning to relax within it

as a form of stress inoculation,

that’s great and works quite well for that purpose.

And there’s a reason why cold exposure is used

in a variety of forms of military stress inoculation,

most famous of which, of course,

is the Navy SEAL BUDS test, really,

which is screening procedure for becoming a SEAL,

involves a lot of exposure to cold water.

However, if you’re interested in using cold exposure

for fat loss and thermogenesis,

you want to do the exact opposite thing.

There was a paper published in Nature two years ago,

which showed that cold-induced shiver,

the actual physical shiver,

activates the release of a chemical in the body

from muscle called succinate, S-U-C-C-I-N-A-T-E.

Succinate travels in the bloodstream

and then goes and activates a particular category of fat,

not the typical kind of pink or white fat

that we think of as like blubber in humans,

the stuff that people seem to generally want less of,

except for those genetic freaks

that seem to have none of it,

depending on what they consume, congratulations.

Brown fat is called brown fat

because it’s actually dark under the microscope.

It’s rich with mitochondria

and it exists mostly between the scapulae

and in the upper neck.

And it generates thermogenesis and heat in the body.

It’s rich with a certain category of adrenergic receptor.

Incidentally, epinephrine binds to adrenergic receptors.

These brown fat cells increase metabolism.

It’s called brown fat thermogenesis and cause fat burning,

burning of other kinds of fat, the pink and white fat.

So what does this all mean?

This means if you want to use the ice bath

in order to increase metabolism, shiver away.

If you want to use the ice bath or cold shower

in order to stress inoculate, resist the shiver

and learn to stay calm or quote unquote muscle through it.

Now, I don’t know that anyone’s ever really talked

about this publicly because I think the data are so new.

And I think that people assume

that the ice bath or cold exposure is just one thing.

Here, I’ve talked about it three ways

to shift your circadian rhythm

depending on whether or not you’re doing it early in the day

while your temperature is still rising or at its peak

or after that peak in order to extend the perception

of your day as continuing and make you want

to go to sleep later and wake up later.

Now, and then the third way of course

is to either activate brown fat thermogenesis

and increase metabolism.

I suppose the fourth way would be

to increase stress tolerance or stress threshold.


But remember, temperature is the effector

of circadian rhythms.

Light is the trigger.

The suprachiasmatic nucleus is the master circadian clock

that mediates all these changes.

Also influenced by non-photic influence

like exercise and feeding and things of that sort.

But temperature is the effector.

Now, you can also shift your circadian rhythm with eating.

When you travel and you land in a new location

and your schedule is inverted 12 hours,

one way that we know you can shift your rhythm more quickly

is to get onto the local meal schedule.

Now, that probably has to do with two effects.

One are changes in temperature,

eating-induced increases in body temperature.

Now you should understand why that would work.

As well as eating has this anticipatory secretion

of beta, of hypocretin orexin

that I talked about it earlier.

So if this is getting a little too down in the weeds,

don’t worry about it.

I will get more into this in episode four

of how to shift one’s rhythm.

But I would love for people to understand

that light and temperature are the real heavy duty levers

when it comes to moving your circadian rhythm

and sleep times and activity schedules.

And exercise and feeding can help,

but really temperature and light

with light being the primary one are the most important

when it comes to sleep and wakefulness.

Many people asked questions about food and neurotransmitters

and how those relate to sleep, wakefulness and mood,

which is essentially 25 hours of content for me to cover.

But I’m going to try and distill out

the most common questions.

We’ve talked a lot about neuromodulators

like dopamine, acetylcholine and norepinephrine.

You may notice in those discussions

that the precursors to say serotonin is tryptophan.

Tryptophan actually comes from the diet.

It comes from the foods that we eat.

Tyrosine is the precursor to dopamine.

It comes from the foods that we eat.

And then once we ingest them,

that those compounds circulate

to a variety of different cells and tissues.

But it is true that our food

and the particular foods we eat can influence

things like neuromodulator levels to some extent.

It’s not the only way

because there are also enzymes and biochemical pathways

that are going to regulate how much tyrosine

gets converted into dopamine.

And there are elements of the dopaminergic neurons,

the dopamine neurons themselves that are electrical

that have influence on this as well.

But there are a couple fair assumptions that we can make.

First of all, nuts and meats in particular red meats

tend to be rich in things like tyrosine, right?

That tells you right there

that because tyrosine is the precursor of dopamine

and dopamine is the precursor of norepinephrine

and epinephrine,

that those foods tend to lend themselves

toward the production of dopamine and epinephrine

and the sorts of things

that are associated with wakefulness.

Now, of course, the volume of food that we eat

also impacts our wakefulness.

If we eat a lot of anything,

whether or not it’s ribeye steaks, rice or cardboard,

please don’t eat cardboard,

your stomach if it’s very distended

will draw a lot of blood into your gut

and you will divert blood from other tissues

and you’ll become sleepy.

So it’s not just about food content,

it’s also about food volume, all right?

Fasting states generally are associated

with more alertness, epinephrine and so forth.

And fed states are generally associated

with more quiescence and relaxation,

serotonin and the kind of things

that lend themselves more towards sleep

and less toward alertness.

Foods that are rich in tryptophan

tend to be things like white meat turkey

but also complex carbohydrates.

So if you like, you can start experimenting

depending on what foods you eat.

You can start experimenting with carbohydrate rich meals

for accessing sleep and more depth of sleep.

This is actually something I personally do.

I tend to eat pretty low carb-ish during the day.

I actually fast for until about noon,

not because I have to work to do that

but because I’d rather just drink caffeine and water

during that time.

And then sometime around noon,

I can’t take it anymore and I’m hungry

and I eat and I try and eat low carb-ish

unless I’ve worked out extremely hard

in the previous two hours, which I rarely do,

although I do sometimes.

And that meal is then designed to prolong

my period of wakefulness into the late afternoon.

And then sometime around dinnertime,

which for me is around 6.30, 7 p.m, 8 p.m,

sometimes as late as 9 p.m,

I tend to eat things like white meat, fish, pastas, rice,

that kind of thing.

My favorite food of all for accessing tryptophan

is actually a starch.

It’s actually a vegetable, it’s the croissant,

which is my favorite vegetable.

I don’t eat those all the time, but I love them.

And they seem to increase dopamine as well.

Never actually done the mass spectrometry on a croissant,

but they definitely increase tryptophan

and relaxation for me.

In all seriousness, low carbohydrate

slash fasted slash ketogenic diets

tend to lend themselves toward wakefulness

by way of increasing epinephrine, norepinephrine,

adrenaline, dopamine, and things of that sort.

Carbohydrate-rich meals,

and I suppose we should talk about meals as opposed to diet,

tend to lend themselves more toward tryptophan, serotonin,

and more lethargic states.

There is very limited evidence that I am aware of

that carbohydrates should be eaten at one time a day

as it relates to metabolism, et cetera.

I’m sure that will open up a certain amount of debate.

If you work out very hard and you deplete glycogen,

then this all changes.

So some people are working out very hard

and depleting glycogen, other people are not.

That gets way outside the context

of this particular podcast.

But yes, indeed, different foods can bias

different neuromodulators and thereby can modulate

our waking or our feelings of lethargy and sleepiness.

There are a couple effects of food that are independent,

or I should say a couple effects of eating,

because the food won’t do it

when it’s sitting across the table,

but of eating that are powerful for modulating

circadian rhythm, wakefulness, et cetera.

And that’s because every time we eat,

we get eating-induced thermogenesis

regardless of what we eat.

Now, the eating-induced thermogenesis

and increase in metabolism,

which is an increase in temperature, really,

is probably greatest for amino acid-rich foods like meats,

but also other types of foods.

It’s a minimal increase in body temperature

compared to, say, cold exposure or exercise.

Now, whether or not it’s a quarter of a degree

or a half a degree or a degree,

it really depends on the individual.

And of course, there are blood sugar effects.

There are things like whether or not

you are type 1 or type 2 diabetic,

whether or not you’re insulin resistant,

whether or not, like, there’s a kid

who interns on the podcast here who’s 17 years old,

and I’m convinced that he can eat anything,

and he just seems to burn it up, and he’s growing.

Every time, actually, the other day,

he walked into the other room, and two days later,

he walked out of the same room.

He came out in between, of course,

but, and I was like, you grew.

He was like, you know, but he’s at that stage

where he’s just growing.

Food is going to affect a teenager very differently

than it’s going to affect a full-grown person.

So in general, starchy carbohydrates,

white meat such as turkey, some fish,

increased tryptophan, therefore serotonin,

therefore more lethargic states, more calm.

Meat, nuts, and there are probably some plant-based foods

that I’m not aware of, and I apologize,

I should read up on this, that also are high in tyrosine

that can increase things like dopamine,

norepinephrine, epinephrine, alertness.

So you can vary these however you like.

Most people, I think, are eating a variety of these things

in given meals, and there are other parameters

of nutrition that are important too.

Volume of food, for the reason I mentioned before,

the volume of food in the gut.

Less food in the gut, whether or not it’s empty

or a small amount of food,

will tend to correlate with wakefulness.

Large volumes of food of any kind

will tend to correlate and drive the calming response,

and that’s by way of this nerve pathway called the vagus.

We actually have sensory fibers in the gut

that communicate to a little protrusion of neurons

that sit right next to the jugular

called the no-dose ganglia, N-O-D-O-S-E.

Unlike Costello, it’s no-dose, right now he’s all-dose.

No-dose actually means having many protrusions,

and it’s like kind of a lumpy collection of neurons.

A ganglia is just a collection of neurons,

and then it goes into the brain stem,

and then forward in the brain to the areas of the brain

that are involved in production of various neuromodulators.

So what we eat and the volume of food

are both signaling to the brain.

It’s not just one or the other.

And then there’s also this eating-induced thermogenesis,

and now you know from the discussion about temperature

that if you’re eating early in the day,

you’re tending to shift your rhythm earlier

so that you’ll want to wake up earlier the next day.

If you’re eating very late in the day,

even if you can fall asleep after that,

there’s a tendency for you

to want to sleep later the next day.

Now, this, of course, is all going to be constrained

by when your kids need to eat,

when your spouse needs to eat,

when your friends need to eat, or if you live alone,

or what other things you’re doing.

If you’re like me and you kind of don’t eat until noon,

then eat sometime around noon,

and then I’m terrible about meals.

I just start eating the ingredients

while I’m supposed to be cooking,

and then eventually they’re all gone,

and I guess that’s a meal.

It varies.

Some people are neurotically attached

to a particular meal schedule.

Some people are not.

I take my light exposure schedule

far more seriously than I take my meal schedule,

although, in general, I try and eat healthy foods

for the most part, croissants included.

I was asked several times whether or not

men and women, or males and females,

differ in terms of these neurotransmitter phenotypes

and the rhythms of sleep and temperature.

You know, we could probably devote a whole month,

and we probably will devote an entire month

to what are called sex differences,

because those tend to be related to things

we absolutely know, like XX or XY chromosomes,

or XYY in some cases, or XX chromosomes,

as opposed to gender, sex, and karyotype, as we call it.

Genetic makeup is crystal clear.

There are things that correlate with one or the other,

but it’s complicated, and it’s not something

that’s been explored in what I think is enough detail.

Actually, recently, I guess it was about five years ago,

the National Institutes of Health made it a mandate

that all studies use sex as a biological variable,

and actually explore both sexes of mice,

both sexes of humans when doing any kind of study,

because there was a bias towards only using male animals

or male subjects prior to that time.

So a lot of data are now coming out

revealing important sex differences

that I think are going to have powerful impact

on health practices, et cetera, response to drugs,

response to different sleep schedules, et cetera.

Perhaps the most salient and obvious one

is that during pregnancy,

females experience a whole range

of endocrine and neuro effects,

and we definitely will devote a month to pregnancy

and childbirth and child rearing.

And for that, I’d really like to bring in some experts.

I’ve got terrific colleagues at Stanford and elsewhere

that work on these things,

so that we can go into those in more depth.

So I’m not blowing off those questions.

I’m just kind of pushing them down on the road a little bit

where I can give you a more thorough answer.

So as we finish up,

I just want to offer you the opportunity to do an experiment.

We’ve talked about a lot of variables

that can impact sleep and wakefulness.

And in keeping with the theme of the podcast,

we are going to continue to talk about sleep and wakefulness

and tools for those and the science behind those tools

as we go forward.

But there are really just four simple parameters

that you have control over

that you can immediately start to record

and take note of

just to see how you’re doing with these things

with no judgment or perhaps no change

to what you’re actually doing.

It might be interesting, just a suggestion,

to write down for each day

when you went outside to get sunlight

and when you did that relative to waking.

So you would write down,

the way I do this on my calendar is I’ll write down that,

I don’t get exact about it.

I might say, I woke up at 6.15

and then I, it’s I’ll put a W, 6.15

and then SL for sunlight.

Now you sometimes get outside right away.

Other times I’m less good at that

and I’ll go out around, I don’t know, let’s say seven.

And for how long?

Maybe like 10, 15 minutes or so.

And then I’ll put a little check

at roughly the times that I eat my so-called meals.

Although as I mentioned,

sometimes my meals are a bunch of small checks

that just kind of extend through the late hours of the day.

Yours might be more confined to certain times.

And then you might just take note of when you exercised,

just put down an E for when you exercise,

weight training or aerobic exercise.

And you might note when you might’ve felt chilled or cold

if you do, or you might’ve felt particularly hot

or if you woke up in the middle of the night

when you felt particularly hot.

And then the last thing you might want to do

is just write down if and when

you did a non-sleep deep rest protocol, NSDR protocol,

that could be meditation, that could be yoga nidra,

that could be hypnosis,

anything that you’re using to deliberately

teach your nervous system how to go from more alertness

to more calmness in the waking state.

Even if it’s waking up in the middle of the night

and doing an NSDR protocol or in the afternoon

or first thing in the morning to recover some sleep

and ability to perform DPOs that you might’ve lost

from a minimal or poor night’s sleep.

So you’re gonna write down when you woke up,

when you viewed sunlight,

that might be in the morning and the evening

or just the morning,

hopefully it’s the morning and the evening,

when you exercised, when you ate your meals

and using a simple record-keeping scheme

like W for waking, SL for sunlight.

Maybe you come up with a system where it’s a check

or an X or something for exercise.

This is not designed to make you neurotically attached

to tracking all your behaviors and everything you do.

I, for instance, don’t track what I eat in particular.

I kind of know what works for me

and I just try and stay within that range.

But by doing this,

you can start to reveal some really interesting patterns.

Patterns that no answer that I could provide you

about any existing tool or protocol could counter.

It’s really about taking the patterns of behaviors

of waking and light viewing and eating and exercise

and superimposing that on what you’re learning

in this podcast and elsewhere, of course,

and what you already know.

And trying to see where certain problems

or pain points might be arising.

Maybe you’re eating really late in the day

and you’re waking up in the middle of the night really warm.

Well, now you would say, well, that could be due

to kind of an increase in temperature

that is extending my day.

Or maybe you start to find that using cold exposure

early in the day is great for you, but using it late,

if it’s too late in the day, that’s not great.

Or if you’re into the sauna or even like some people,

including myself, if I take a hot shower

or sit in a hot tub or a sauna late at night,

well, then I get a compensatory decrease in body temperature

and I sleep great, provided I hydrate well enough

because that can be kind of a dehydrating thing

to sit in hot conditions.

But if I do the sauna early in the day,

unless I exercise immediately afterward,

then I tend to get the temperature drop,

which makes sense because we can get in the sauna,

you get vasodilation, you throw off a lot of heat,

and then you generally get a compensatory drop

in temperature.

If you do that early in the day,

that’s right about the time that that temperature

is trying to entrain the circadian clocks of your body.

That’s what happens to me.

Other people, it might be slightly different.

And some people have more resilient systems than others.

So I just encourage you to start becoming scientists

of your own physiology, of your own brain and body,

and seeing how the various tools that you may

or may not be using are affecting your patterns of sleep,

your patterns of attention and wakefulness.

It’s vitally important that if you do this,

that you know that it’s not about trying to get

onto an extremely rigid schedule.

It’s really about trying to identify variables

that are most powerful for you,

and that push you in the direction that you want to go,

and changing the variables that are pushing your body

and your mind in the directions that you don’t want to go.

Self-experimentation is something that should be done

slowly, carefully.

You don’t want to be reckless about this.

And this is where I would say manipulating

one or two variables at a time is really going to be best,

as opposed to changing a dozen things all at once,

to really identify what it is that’s most powerful for you.

As always, thank you so much for your questions.

We are going to continue to answer questions.

I certainly didn’t get to all of them,

but we tried to get to most all of the ones

that were frequently asked.

Episode four of the podcast,

I’m going to get into shift work, jet lag,

and age-dependent changes in sleeping and wakefulness

and cognition.

So for those of you with kids,

for those of you that are kids,

for those of you with older relatives,

or who might be older, meaning probably when you start

to get into late 60s, 70s, and 80s,

is when there’s some marked biological shifts

in temperature regulation and things that relate to sleep.

And for those of you that travel,

we’re going to talk about jet lag.

The shift work discussion might seem only relevant

to those that work nights, but actually that’s not the case.

Most people, because of the way they’re interacting

with devices, are actually in a form of shift work now,

where the days are certainly not nine to five,

so-called banker’s hours, and then the lights are out

at nine and they’re asleep until 5 a.m.

Some people have that schedule, most people do not.

So episode four, we will go deeply into shift work,

jet lag, age-dependent changes in sleep alertness

and cognition, and I will touch back

on a few of your questions.

But don’t think that if your question wasn’t answered

during these office hours that we won’t get to it.

I absolutely will at some point.

In addition to that, several of you have graciously asked

how you can help support the podcast,

and we very much appreciate that.

You can support the podcast by liking it on YouTube,

by subscribing on YouTube,

by recommending the YouTube videos to others,

as well as subscribing and downloading the podcast on Apple,

where you can also leave a review,

and on Spotify, or all three, if you like.

You can also help us by supporting our sponsors.

So check out some of the sponsor links that were described

at the beginning of the episode.

And in general, recommending the podcast to people

that you know and that you think would benefit

from the information would be terrific.

And as mentioned at the beginning of today’s episode,

we are now partnered with Momentous Supplements

because they make single ingredient formulations

that are of the absolute highest quality,

and they ship international.

If you go to slash Huberman,

you will find many of the supplements

that have been discussed on various episodes

of the Huberman Lab podcast,

and you will find various protocols

related to those supplements.

As always, I will be continuing to post on Instagram.

You can expect another podcast episode out next Monday

about the topics that we’ve been discussing this month.

And above all, thank you for your interest in science.


comments powered by Disqus