The Diary Of A CEO with Steven Bartlett - Moment 141: What Coffee Is REALLY Doing To Your Sleep!: Matthew Walker

Episode Date: December 22, 2023

In this moment, sleep expert and author of ‘Why We Sleep’, Matthew Walker discusses the 3 main reasons why caffeine is so terrible for sleep. Firstly, is that the impact of caffeine lasts long after drinking a cup of coffee. Caffeine has a quarter life of between 10 to 12 hours, which means if you have a cup of coffee at midday, a quarter of that caffeine is still in your brain at midnight. Secondly, as a stimulant, caffeine mutes the chemical, adenosine, which is in charge of sleepiness. However, the adenosine is still there and builds, so when caffeine leaves your system you get a caffeine crash, which is all the sleepiness that has been built up hitting at once. Finally, caffeine blocks deep sleep by between 15 to 30%. So even if you are able to fall asleep after drinking coffee, it will be poor quality sleep, and you lose out the amazing benefits of deep sleep, such as: regulating your cardiovascular system, replenishing the immune system, and securing new memories into your brain. However, Matthew doesn’t say that people should completely give up coffee, but instead the main thing to look out for is how much you drink and the timing of when you drink it. Listen to the full episode here - https://g2ul0.app.link/FlNqF0boIFb Watch the Episodes On Youtube - https://www.youtube.com/c/%20TheDiaryOfACEO/videos Matthew: https://www.sleepdiplomat.com https://www.instagram.com/drmattwalker/?hl=en

Quick one, just wanted to say a big thank you to three people very quickly. First people I want to say thank you to is all of you that listen to the show. Never in my wildest dreams is all I can say. Never in my wildest dreams did I think I'd start a podcast in my kitchen and that it would expand all over the world as it has done. And we've now opened our first studio in America, thanks to my very helpful team led by Jack on the production side of things. So thank you to Jack and the team for building out the new American studio.

And thirdly to Amazon Music who, when they heard that we were expanding to the United States and I'd be recording a lot more over in the States, they put a massive billboard in Times Square for the show. So thank you so much, Amazon Music. Thank you to our team. And thank you to all of you that listened to this show. Let's continue. Caffeine will hurt your sleep in probably at least three ways some of which you most people are not aware of the first issue is the duration of its action so caffeine has what we call a half life of about five to six hours in other words after about five to six hours half of that caffeine is still in your system.

What that means is that caffeine has a quarter life of somewhere between 10 to 12 hours. So if you have a cup of coffee at noon, at midday, a quarter of that caffeine is still in your brain at midnight. So having a cup of coffee at noon, and it's hyperbole in truth, probably, or it's a little bit hyperbolic, but it's almost the equivalent of a coffee at noon is the equivalent of, you know, tucking yourself into bed. And just before you turn the light out, you swig a quarter of a cup of coffee and you hope for a good night of sleep. And it's probably not going to happen. So that's the first thing to keep in mind is the timing of caffeine.

The second is that caffeine is a stimulant. Now everyone knows this. Everyone knows that caffeine can make you more alert and more awake. By the way, how does it do that? It comes back to adenosine, which is the chemical that we spoke about, the sleepiness chemical. It's no coincidence that those two things sound the same at the end of the name caffeine and adenosine caffeine will actually race into your brain and it will latch on to the adenosine receptors the welcome sites in your brain and it has very sharp elbows and it will force away the adenosine from those receptors and it will hijack those receptors. Now, at this point, you may be thinking, well, hang on a second, if it's latching onto those sleepiness chemical receptors, shouldn't caffeine make you more sleepy? And the answer is no, because what it does is it just latches onto the receptor and

it inactivates it essentially. So it masks the receptor. What caffeine does then is race into your brain. You've got all of this sleepiness at 9 p.m. or 10 p.m. You have an espresso because you're trying to power through and finish the report or, you know, the presentation for your sort of your pitch deck for your startup company. And that caffeine races in, it latches onto the adenosine receptors and blocks the signal of adenosine. So now your brain was thinking, I'm starting to get tired. It's 10 PM. But now all of a sudden, that signal is blocked. And caffeine is like hitting the mute button on your television remote controller. It just mutes the signal of sleepiness. So now you think, well, no, I don't feel sleepy anymore. And here's the

danger that even though, well, when the caffeine is in your system and it's latched onto the receptors, that adenosine is still there. It's not going away. In fact, if anything, during the course of the caffeine in your system, it continues to build and build. And now when the caffeine finally gets metabolized and excreted out of your system, not only do you go back to the sleepiness that you had many hours before it's that plus all of the adenosine sleepiness that's been building up during that time in between so you get hit with this huge tsunami wave of sleepiness and that's what we call the caffeine crash so the one of the issues, so that's sort of caffeine in terms of how it works and its timing. Another issue is that it creates anxiety, just as you said. And anxiety is probably one of the greatest enemies of sleep. It's one of the principal

reasons that underlies insomnia is a physiological state of anxiety, that your fight or flight branch of the nervous system is ratcheted up. That's caffeine will do it needs to do the opposite for you to fall asleep that's why you can have what we call the tired but wired phenomenon where you say i'm so desperately tired i am so tired but i'm just so wired that i can't fall asleep it's because your nervous system is too amped up caffeine will trigger that amping up. Then at that point, if you're struggling to fall asleep because you've got too much caffeine on board, it is what we call anxiogenic. So now you start to worry.

And the last thing you need to do when your head hits the pillow for good sleep is worry. Because when you start to worry, you start to ruminate. And when you ruminate, you catastrophize. And when you catastrophize, you're dead in the water for the next two hours when it comes to sleep. Because we have this sense that, you know, things at night, in the darkness of night, are so much bigger than they are in the brightness of day. And we start worrying, you know, know in this modern era we're constantly on

reception and very rarely do we do reflection and unfortunately the only time when we typically do reflection is when we turn off the light and our head hits the pillow and that is the last time you want to be doing reflection so that's the the second problem with caffeine it's anxiogenic it only makes you sort of almost like the Woody Allen neurotic of the sleep world. The final part of caffeine is that it's very good at blocking your deep sleep. So we've done a number of these studies where we'll give people a standard dose of caffeine, let's say 150 milligrams, 200 milligrams, which is probably, you know, a cup and a half of good, strong coffee. And then we put you to bed and we look at the amount of deep sleep and it will strip away your deep sleep by about somewhere between 15 to 30%.

Now to put that in context, to drop your deep sleep by 30%, I'd probably have to age you by about 40 years for zero, or you could do it every night with an espresso with dinner. And that's one of the problems that people will say to me, look, I'm one of those people who I can have two espressos with dinner and I fall asleep fine and I stay asleep. So no harm, no foul. Well, not necessarily because even if you fall asleep and you stay asleep, you're not aware of the lack of the deep sleep that you're not getting because of the caffeine. And so now you wake up the next day and you think, well, I don't remember having a hard time falling asleep. I don't remember waking up, but now I'm reaching for two or three

cups of coffee the next morning rather than my standard one cup of coffee because I don't feel refreshed and restored by my sleep because I was lacking the amount of deep sleep. And deep sleep, what does that rob us of? The lack of deep sleep. So lack of deep sleep, deep sleep is critical for regulating your cardiovascular system. It's the time when we do replenish the immune system. It also regulates your metabolic system. So it controls the hormones such as insulin that will regulate your blood sugar and you will become blood sugar dysregulated without sufficient deep sleep. Upstairs in the brain, deep sleep will strengthen and consolidate and secure new memories into your brain. They will prevent those memories from being forgotten. Deep sleep is also the time when we cleanse the brain of metabolic toxins, particularly the toxins that are related to

Alzheimer's disease. So getting a lack of deep sleep is, I would say, a non-trivial thing in that regard. But I don't want to be also puritanical here, and this is where I'm going to change my title tune. I am not here to tell anyone how to live their life. I have no right to tell anyone how to live their life. I'm just a scientist. All I want to try and do is gift you the science and the knowledge of sleep

so that you can make an informed choice. And after all, and the same is true for alcohol too and sleep, you know, life is to be lived to a certain degree. You know, no one wants to be the healthiest guy in the graveyard. I don't want to be that way too. I want to live life just with moderation. The reason I don't drink caffeine is not because I'm so puritanical. I want to be the poster child of good sleep. I love the smell of

freshly ground coffee in the morning. It's a great ritual. It's just that I've run my genetics and I am one of the slow caffeine metabolizers. So you can do these genetic kits online and they will tell you, are you a slow metabolizer or a fast metabolizer? So that's the variability. That's why some people say, look, I'm not. Why do I now favor coffee? I was actually quite anti-caffeine in coffee when I first came out with the book, just looking at the studies. But now the data is immensely compelling.

The health benefits associated with coffee are undeniable. Study after study after study. And we can put them all together in this big, what we call a meta-analysis study. And it is so strikingly clear that coffee, drinking coffee is a good thing for you from a health perspective. Two things to say about that. The first is that it's got nothing to do with the caffeine. And a lot of people have sort of rightly challenged me to say, look, you say how problematic sleep can be when you're drinking too much caffeine,

but yet coffee is associated with many of the same health benefits that sleep is associated with, but coffee is supposed to hurt your sleep. How do you reconcile those two, Matt Walker? And the answer is very simple, antioxidants. Because it turns out that the coffee bean contains a whopping dose of antioxidants. Things such as, it's what's got other things such as cathestol, but it's got a bunch of incredible antioxidants. Probably the most powerful of them in terms of the coffee bean is something called chlorogenic acid. Now don't worry, it's not chlorine, it's not chloride, it's not bleach. Chlorogenic acid is very different. And what's happened in the modern world is that we have and struggle with our diet so much because we don't eat enough whole foods, etc.

So what's happened is that the coffee bean has been now asked to carry the Herculean weight of all of our antioxidant needs on its shoulders. And where most people get the majority of their antioxidants is by way of drinking coffee that's why coffee is associated with so many health benefits and it's not the caffeine case in point if you look at the studies with decaffeinated coffee you get very similar health benefits again it's not the caffeine it's the coffee. So the bottom line here is drink coffee, but I would say the dose and the timing make the poison. So try to limit yourself to about two cups of coffee, three cups of coffee maximum, because if you look at the health benefits, by the way, it's a dose, it's not a dose response where it's linear, where the more and more coffee you drink,

the more and more healthy you become. It peaks at about two to three and then actually starts to go down in the opposite direction for lots of reasons that we can speak about. So dose and the timing make the poison when it comes to coffee. So you drink decaf?

So I do drink decaf. So I will drink coffee just because I love the smell and I do enjoy the taste of it, but I drink decaffeinated coffee I would love to drink caffeinated coffee too because I you know I'm sure it would be interesting because I work out every day and I work out every morning and so many of the health coaches that I speak with and health professionals say you know you should definitely get a shot of caffeine in it boost your workout and actually the data on that is pretty clear too that you're lifting for example in the gym and your metabolic

activity is stronger when you've had pre-caffeine doses but it's also stronger when you sleep so but exactly and that's the problem so and sleep is i would argue much more beneficial to health. And if you're trying to work out or you're trying to be an athlete or perform, sleep will trump caffeine five ways till Tuesday. I mean, sleep is probably the very best legal performance enhancing drug that we know of that not enough athletes are abusing.