The Diary Of A CEO with Steven Bartlett
No.1 Sleep Expet: Magnesium Isn’t Helping You Sleep! This Sleep Habit Increases Heart Disease 57%
17 Nov 2025
Chapter 1: What issues arise with magnesium supplementation for sleep?
Here's the problem with magnesium supplementation when it comes to sleep. The first thing to note is that most forms of magnesium don't cross the brain barrier and sleep is produced by your brain. So how can something that doesn't get into your brain affect brain process? All you're doing is creating probably expensive urine.
However, there is one form of magnesium that seems to have some evidence in favor of it, which we can speak about, but it doesn't stop there.
There's so much new evidence that we have, including this myth of eight hours, my fear about giving melatonin to kids while you keep them waking up in the middle of the night, and the invention of the first new class of sleeping medication that I actually favor, and most people are not aware of it.
Okay, let me write this down. Matthew Walker is back. And the world-renowned sleep expert and neuroscience professor is sharing brand new research to combat the sleep loss epidemic and help you get the perfect night's sleep.
As a society, we have struggles with sleep at night due to many reasons, but no one teaches us this stuff.
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Chapter 2: How does sleep timing affect health risks?
And it's things like So you go to bed at 11 one night, 1 a.m. the next night, then 10.30 p.m. the next night.
Chapter 3: What is sleep banking and how can it help during low-sleep periods?
And it's remarkable how many people do this. Studies have shown that you are statistically 49% more likely to prematurely die versus those people who are most regular in terms of going to bed and waking up at the same time. And worse, they had a 57%. 10% cardiometabolic disease risk increase. What the?
Chapter 4: What are the three impactful strategies to improve sleep quality?
Science really teaches us that there are four pillars of good sleep. And then there's this incredible new study looking at sleep banking. And this is remarkable for people who are facing a sprint at work or a medical doctor about to go on call for the next 40 hours, a new parent, and we can go through all of that.
But if you were to push me to say the three most impactful things that you can start doing tonight to start sleeping better, it would be...
Just give me 30 seconds of your time. Two things I wanted to say. The first thing is a huge thank you for listening and tuning into the show week after week. It means the world to all of us and this really is a dream that we absolutely never had and couldn't have imagined getting to this place. But secondly, it's a dream where we feel like we're only just getting started.
And if you enjoy what we do here, please join the 24% of people that listen to this podcast regularly and follow us on this app. Here's a promise I'm going to make to you. I'm going to do everything in my power to make this show as good as I can now and into the future.
We're going to deliver the guests that you want me to speak to and we're going to continue to keep doing all of the things you love about this show. Thank you. Dr. Matthew Walker. Here in front of me, I have these cards, which I'm going to reveal a bit later, but these kind of hold what you consider to be the four pillars of great sleep.
But you also spend much of your professional career just studying the brain generally to understand human performance and how we can... change our lifestyles, and also introduce some of these new sort of treatments to improve how our brain performs. And I want to talk about all of that as well.
But to start, for anyone that is unfamiliar with you and has been hiding under a rock, how do you summarize who you are professionally? the sort of academic references you're drawing on and the experiences and research you've done so that the viewer listening at home understands the full world that you operate in, study and have experienced.
I am a neuroscientist by trade, but my speciality is sleep, the effects of sleep on the brain and the body. And I've probably spent about the past two decades trying to understand exactly why do we sleep? Because 50 years ago, the crass answer to the question, why do you sleep, was the following. You sleep to cure sleepiness.
Which is the factious equivalent of saying, well, you eat to cure hunger. No, you don't eat to cure hunger. You eat to support all sorts of physiological and biological benefits. But now, and this is not due to my research, this is all of the incredible colleagues whose sort of shoulders that I stand on. We've now had to upend the question.
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Chapter 5: What is the tired but wired phenomenon and how does it affect sleep?
I see a lot of people coming to the sleep center where I'm at, and they have what I call the tired but wired phenomenon, where they come to me and they say, I am so tired. I am so, so tired, but I'm just so wired emotionally and from a nervous perspective that I can't fall asleep. And let's say that you've done, let's say, you know, an onstage event. And it's incredible.
You've got that onstage buzz. You come offstage at 11 p.m. And normally you'd be fast asleep. But you know you are so wired, it doesn't matter. You are tired, as tired as can be. But you're so wired, you can't fall asleep. That's the fight or flight branch being switched on. And you just can't fall asleep. You need to push it back off.
Phosphatidylserine and ashwagandha will both push you back over into the more quiescent, what we call parasympathetic nervous system branch. That's good.
Chapter 6: How do cortisol levels impact sleep and waking processes?
However, they also will reduce cortisol, and cortisol is a wake-promoting hormone. Cortisol is fine. It gets a bad rap. You need to have your cortisol start to spike a few hours before bed, and it helps with the waking-up process. It's wonderful. Every day we have a cortisol spike that starts happening before we wake up. It's one of the things that helps us wake up.
And then it builds us to this beautiful crescendo mid-morning where you should be awake and not needing caffeine. And it drops before bed. And then it starts to peak in the sort of middle, early afternoon. And in fact, usually peaks at the late morning hours, I should say. And then it will start its awesome sort of downswing.
And what you see is that right before you go to bed, cortisol should hit its lowest point, what we call its nadir, its lowest trough. What's interesting, by the way, just as an aside, is that insomnia, we can classify usually as at least one of two different types.
Chapter 7: What are the two types of insomnia and how do they differ?
There's actually multiple, but let's just say of those multiple, there are two types. One is called sleep onset insomnia. I can't fall asleep. The other is sleep maintenance insomnia. I can't stay asleep. When they've looked at people's cortisol on a 30-minute by 30-minute basis on the 24-hour clock face, we go through just what we described. Just before we wake up, we get this rising cortisol.
It peaks late morning, and then it drops down. And right before bed, our cortisol is almost at its lowest point. With insomnia patients, they show exactly the same thing. A beautiful rise, in the late morning hours, it starts to come down, but then you see two anomalies. Right before bed, it goes back up.
And then in the middle of the night, even when it's starting to rise, it will have this abnormal spike right in the middle of the night too. And what we believe is that that may in part explain sleep onset insomnia. Cortisol should be coming down and it should stay low right before we go to bed, but then it jumps back up in insomnia patients. I can't fall asleep.
And then it continues to stay low throughout the first half of the night, but then it also spikes in insomnia patients. I can't stay asleep.
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We were talking about regularity, timing and all these things and quality and quantity. But one of the things I learned from your work is that that last hour is potentially the most important hour of me being in bed. And I say this in part because my girlfriend, she would wake, she would have about six hours, six and a half hours sleep. She sleeps very, very well. Perfect sleeper.
But she'd always get up really, really, really early. And... In part, that was because of the guilt that I talked about. But I had a conversation with her about the guilt. And I said, just stay in bed as long as you need to stay in bed. Like, just have that extra eighth hour. And in part, that's because I learned that the further we go in sleep, the more REM we're getting.
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Chapter 8: What are the implications of genetic short sleepers on society?
Physical recovery.
Physical recovery, but mental too. It's during deep sleep that you take newly minted memories that you've learned and you hit the save button on those memories so that you don't forget. Deep sleep essentially is going to future-proof the information that you just learned today. It transfers information from a short-term storage vulnerable reservoir to a more permanent long-term storage site.
It's during deep non-realm sleep when we have this communication. So think of those deep, powerful, slow brainwaves like long wave radio station when you used to tune into a radio station in the car. You get huge ability for information transfer across long distances, across huge paths in the brain. It's amazing. So we've gone from light non-REM. Then we go down into deep non-REM.
We'll stay there for about 15 or 20 minutes. Then we'll start to rise back up again. We'll go back into stage two non-REM sleep.
Wait, we've gone from one, two, three to two?
Yes. So we've gone, think about it more almost like a roller coaster ride. So we go from light non-REM. And then we go down into stage two non-REM. Then we go down into deep sleep. And then we're going to rise back up into light stage two non-REM sleep. We're going to stay there. And after about 70, 80 minutes, you're going to pop up and you'll have a short REM sleep period.
Oh, okay. Like this.
And this is beautiful. So this is what we call a hypnogram.
I'll put this on the screen for anyone.
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