Caffine will hurt your sleep in probably at least three ways, some of which most people are not aware of. The first issue is the duration of its action. Caffine has what we call a half-life of about 5-6 hours. In other words, after about 5-6 hours, half of that caffeine is still in your system. What that means is that caffeine has a quarter-life of somewhere between 10-12 hours. If you have a cup of coffee at noon, at midday, a quarter of that caffeine is still in your brain at midnight. 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 tucking yourself into bed. 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. 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. Caffine will actually race into your brain and it will latch onto 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 laches onto the receptor and it inactivates it, essentially. It masks the receptor. What caffeine does then is race into your brain. You've got all of this sleepiness at 9:00 PM or 10:00 PM. You have an Espresso because you're trying to power through and finish the report or the presentation for your pitch deck for your startup company. And that caffeine races in, it laches onto the adenosine receptors and blocks the signal of adenosine. So now your brain was thinking, I'm starting to get tired, it's 10:00 PM.

But now all of a sudden that signal is blocked and a caffeine is like hitting the Mute button on your television remote controller. It just mutes the signal of sleepiness. Now you think, Well, now I don't feel sleepy anymore. Here's the danger that even though 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. 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. You get hit with this huge tsunami wave of sleepiness, and that's what we call the caffeine crash. That's the caffeine in terms of how it works and its timing. Another issue is that it creates anxiety, just as you said. An anxiety is probably one of the gracious 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 ratched it up.

That's what 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. Caffine 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 angiogenic. Now you start to worry. 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. When you ruminate, you catastrophize. 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 things at night in the darkness of night are so much bigger than they are in the brightness of day. We start worrying. In this modern era, we're constantly on reception, and very rarely do we do reflection. 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.

That's the second problem with caffeine. It's angiogenic, and it only makes you almost like the woody, l and neurotic of the sleep world. The final part of caffeine is that it's very good at blocking your deep sleep. 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 a cup and a half of good, strong coffee. 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 15-30 %. 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. That's one of the problems that people will say to me, Look, I'm one of those people who I can have two Espresso's 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.

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. 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. After all, and the same is true for alcohol too, and sleep, life is to be lived to a certain degree. 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 metabolites. You can do these genetic kits online and they will tell you, are you a slow metabolizer or a fast metabolizer? That's the variability. That's why some people say, Look, I'm pretty immune to caffeine. Others will say, No, I'm not. Why do I now favor coffee?

I was actually quite anti-cafein and 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. We can put them all together in this big, what we call a meta-analysis study. 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. A lot of people have 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. It's got other things such as catheter, 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, et cetera. 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 many health benefits, and it's not the caffeine. Case in point, if you look at the studies with decaffinated coffee, you get very similar health benefits. Again, it's not the caffeine, it's the coffee itself. The bottom line here is drink coffee, but I would say the dose and the timing make the poison. 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 not a dose-response where it's linear, where the more and more coffee you drink, the more and more healthy you become. It piques at about 2-3 and then actually starts to go down in the opposite direction for lots of reasons that we could speak about.

So dose and the timing make the poison when it comes to coffee. So you drink decaf? I do drink decaf. I will drink coffee just because I love the smell and I do enjoy the taste of it. But I drink decafinated coffee. I would love to drink a caffeine coffee too, because 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 should definitely get a shot of caffeine in it and boost your workout. 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-cafein doses. But it's also stronger when you sleep. Exactly, and that's the problem. Sleep isI 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.