morning, which is, I think my mother used to always say to me, You know, go to sleep.

You'll feel better in the morning.

Correct.

You're saying that was real science.

That's extraordinary.

Yeah.

And in fact, there's a wonderful quote by the American entrepreneur, E. Joseph Cossman,

once said the best bridge between despair and hope is a good night of sleep.

Welcome to ZOE Science and Nutrition, where world-leading scientists explain how their

research can improve your health.

Thank you for joining me today.

I really enjoyed your book, you know, Why We Sleep, which I first read quite a few years

ago now when it first came out, and I have to admit, I'm not sure I said this to you

before, but I drove my wife crazy, turning our bedroom into a cave afterward.

So she definitely knows who you are, even though she hasn't yet met you.

Probably for all the wrong reasons, but at least I anoint you as a sleep ambassador for

what you've been doing, Jonathan.

Well, thank you.

I think, as always, it's a bit like with ZOE and Nutrition, you know, I nag at her for

so long about this and eventually get into it, and then she becomes more obsessive than

me.

So, she's on that path with sleep.

But anyway, look, it's great to have you here talking about sleep.

Both your research and I think we're also gonna touch on some of the research that you're

working on together with ZOE.

Now we have a sort of tradition here on the podcast.

We always like to start with a quick-fire round of questions from our listeners, and

the rules are really simple.

You can say yes or no, or a one-sentence answer, but no more.

And we know that scientists always find this challenging.

So are you ready for me to kick off?

I'm ready for the challenge.

All right, so the first question is can bad sleep kill?

Yes.

In multiple different ways through multiple different diseases.

I know we're gonna talk more about that.

Okay.

Is it more important to exercise than to sleep well?

I would say sleep is the foundation on which exercise and nutrition sit.

It's not the third pillar, It's the foundation for those two other things.

And I'm guessing that the people listening to this cold, waking up at five in the morning

to exercise.

We'll talk a little bit about whether that's a good idea.

I think we will.

All right.

Is a short nap in the day okay?

Mostly yes.

If you're suffering from insomnia, no.

Can what we eat affect how we sleep?

Yes.

I have a small child, Matt.

I get woken up in the night.

Is my health doomed?

No.

Simply get sleep whenever you can get it across the day or the night during that time period

of ownership of a young one.

All right, That's great advice, which also sometimes is hard to follow.

So Matt, what's the biggest myth about sleep that most people still believe?

There are so many myths, but I think one of the fun myths that have been busted is that

counting sheep will help you fall asleep.

And there's a great study done here at UC Berkeley, and it wasn't done by me, it was

done by a colleague of mine.

And what they found is that counting sheep not only didn't make you fall asleep any faster,

it actually took you longer to fall asleep when you were counting sheep.

But what they did find was something interesting.

There is an alternative mental strategy.

That strategy is taking yourself on a mental walk, so think about a walk that you know

really well.

Maybe it's a walk in the woods or in the forest, or a hike or a walk on the beach.

and then try to really visualize that to the point of, this is me leaving my front door,

I'm walking down the steps, off I go.

And if you do it in granular detail and move through it, the next thing you remember is

your alarm going off the next morning because you've fallen asleep and it seems to be quite

an effective tool.

So that's one of the many, many myths that we come bust regarding sleep

Brilliant.

Thank you, Matt.

And look, why don't we actually just start right at the beginning there about what is

sleep?

And I know it sounds like a sort of crazy question, right?

Because we all sleep.

I think it remains sort of one of the more mysterious key activities that happen in a

human being.

So could you just sort of kick off with us there?

Yeah, it's bloody bizarre, isn't it,?

I mean, you know, we close our eyes, and then we think that we essentially lose consciousness

and that our body just lies dormant, and then seven to nine hours later we wake up.

Now, that is so understandable and if I didn't know what I know about sleep, I would think

the same.

And as a consequence, I perhaps would say, Well, look, what's the big deal of losing

30 minutes or an hour here or there?

You know, or just going down to six hours because I'm a busy person, or five and a half

hours, because really I'm just missing out on my body, getting some rest, and my mind

is not really doing much.

Nothing further from the truth is the actual fact of it.

Your brain is incredibly active during stages of sleep.

In fact, during some stages, it's up to 30% more active than when you're awake.

More than 30% active than when I'm awake.

That's crazy!

Yeah.

Some parts of your brain, a 30% more active in some stages of sleep than when you're awake.

And then downstairs in your body, there is a radical overhaul.

There is - it's like hitting the reset button on your wifi router, but it just takes seven

to nine hours to do let me just take a step back though, cause I haven't really answered

your question.

What is sleep?

Sleep in human beings, in fact, in all mammalian species is separated into two main types.

On the one hand, we have something called non-rapid eye movement, sleep, and non-REM

sleep.

On the other hand, we have rapid eye movement sleep or REM sleep.

And REM sleep is the principal stage in which we dream.

Now it turns out that non-REM sleep is further subdivided into four separate sub-stages that,

unimaginatively called stages one through four, increase in their depth.

So stages three and four, that a deep sleep that we discussed.

And then stages one and two of non-rem, that's light sleep.

So you may have seen this in some of your sleep trackers where it says, Were you awake,

in light sleep, deep sleep, or REM sleep?

Now those two types of sleep, non-REM and REM will end up playing out in a battle for

brain domination throughout the night, and that cerebral war is going to be won and lost

every 90 minutes.

And then replayed every 90 minutes creating this standard 90-minute cycling architecture

of human sleep on average, in most people.

What's interesting, however, is that the balance, the sort of the cocktail mixer distribution

of non-REM and REM within those 90-minute cycles, changes as you move across the night.

What I mean by that is in the first half of your night, the majority of those 90-minute

cycles are comprised of lots of deep non-REM sleep and very little REM sleep.

But when you push through to the second half of the night, now that shifts and instead

you get much more REM sleep and very little deep sleep.

And Matt, what's all of this for?

So I mean, we definitely get a picture that it's a lot more complex than I guess most

of us imagined, which is, I always sort of felt, Oh, you go to sleep, you wake up.

It's sort of annoying, right?

Like all those hours when you could do something better.

I think you're starting to paint this picture of a lot of complexity.

Why is any of this happening?

Learning memory, emotional brain regulation, brain plasticity downstairs in the body and

overhaul of your cardiovascular system, a replenishing of your immune system, a reregulation

of all of your hormonal systems.

And in fact, 50 years ago, we used to ask the question, Why do we sleep?

And the crass answer at the time was that we sleep to cure sleepiness, which tells you

nothing about, you know, the meaningfulness of sleep.

Now, 50 years later, we've had to upend the question.

We now have to ask, is there any major operation of your brain or is there any major physiological

system in your body that isn't wonderfully enhanced when you get to sleep or demonstrably

impaired when you don't get enough?

And so far the answer seems to be no.

That's amazing.

And so how does that tie in?

You're describing these different stages.

Are they linked to particular elements of the way in which sleep is sort of creating

all of these benefits for us?

Very much so.

So what we've learned is that all of those stages, even some of the light forms of non-REM

sleep, All of those stages of sleep are important.

And so sometimes people will come up to me and say, How do I get more deep sleep?

Or How do I get more REM sleep?

And my question to them usually is, Why do you want to get more REM sleep or deep sleep?

And they'll say, Well, isn't that the good stuff,?

And it turns out, and it's all good stuff, it's just that different stages of sleep will

do different things for your brain and your body.

At different times of night and we can't shortchange the brain on any one of those stages without

suffering some kind of deleterious impairment.

So you need all of these different stages that you're describing because they're each

doing different things for both our mind and sort of the rest of our body.

Is that what you're saying?

Correct.

And when you think about it from an evolutionary perspective, of course, that must be the case

because when we