ZOE Science & Nutrition - Recap: Banish bad sleep with these top tips | Prof. Matt Walker

Episode Date: June 17, 2025

Today we’re talking about sleep. Are you a good sleeper? It’s something we all aim for, yet many of us fall short. And the consequences of a poor night’s sleep go far beyond just feeling groggy the next day. In fact, sleep plays a pivotal role in our long term health - influencing everything from our mood to our immune system, and even how long we live. So how do you get better sleep in a world that never seems to rest? I’m joined by sleep scientist Prof. Matt Walker to unpack the latest sleep science and share his top tips to getting a good nights rests. 🥑 Make smarter food choices. Become a member a zoe.com - 10% off with code PODCAST 🌱 Try our new plant based wholefood supplement - Daily30+ *Naturally high in copper which contributes to normal energy yielding metabolism and the normal function of the immune system 📚 Books from our ZOE Scientists:The Food For Life Cookbook by Prof. Tim Spector Food For Life by Prof. Tim Spector Every Body Should Know This by Dr Federica Amati Free resources from ZOE: Live Healthier: Top 10 Tips From ZOE Science & Nutrition  Gut Guide - for a healthier microbiome in weeks Have feedback or a topic you'd like us to cover? Let us know here Listen to the full episode here

Hello and welcome to Zoey Recap, where each week we find the best bits from one of our podcast episodes to help you improve your health. Today we're talking about sleep. Are you a good sleeper? It's something we all aim for, yet many of us fall short. And the consequences of a poor night's sleep go far beyond just feeling groggy the next day. In fact, sleep plays a pivotal role in our long-term health, influencing everything from our mood to our immune system, even how long we live. So how do you get better sleep in a world that never seems to rest? I'm joined by sleep scientist Dr. Matt Walker to

unpack the latest sleep science and share his top tips to getting a good night's rest. Personally, I have really noticed I'm in my late 40s now that I do not sleep as well as I used to. I used to be someone I would consider myself a really good sleeper and there's no doubt that I'm more easily disturbed, that when I'm disturbed I find it harder to go back to sleep. And I know you have some really great advice for people listening to this who are now saying, you know what, maybe I didn't take sleep as seriously

as I should have done now, I wanna take it really seriously. How can I go and get better sleep? What would your advice be, Matt? Now, I think there's a couple of general tips and you can find most of these on the internet too, but it's good to go over them. The first thing is regularity. I would say if you could just focus on one thing, go to bed at the same time, wake up at the same

time, no matter whether it's the weekday or the weekend. And I'm pretty religious like this, and not because I want to be a poster child for good sleep. It's selfish. If you knew everything I knew about sleep and how important it is, you wouldn't do anything different than prioritizing your sleep, and I do. I would say make sure you're getting somewhere between a seven to nine hour opportunity. Find out what is innately correct for you, which is called your chronotype. Are you a morning type, evening type, or somewhere in between? You need to sleep in harmony with your chronotype

to get the best sleep. So I'm somewhere in the middle, just like the rest of my personality. I'm quite vanilla in terms of my chronotype. So you either a morning type, evening type, or a neutral. And I'm mostly a neutral. I'm kind of somewhere between an 11 to 1130, kind of, you know, 730, 745 wake up time, which puts me in the neutral category. If I were to go to bed at 9 p.m. and then wake up eight hours later, or I were to go to bed at 4 a.m. and wake up eight hours later versus my natural eight hour sleep window. Well, it's eight hours. So what's the difference that there's surely there's no difference.

Well, there's a big difference because in one of those three scenarios, I will have been sleeping in sync with what my biological rhythms want me to do. And the other times I will be out of sync and I won't sleep as well. But the first message is regularity. And Matt, just a question because I know that we'll get a flurry of these questions afterwards. How do you find out your chronotype so that you know that you can be sleeping in line with that?

If you want to do the detailed assessment, you can go onto Google and you can search for something called the MEQ, which stands for Morningness, Eveningness, Questionnaire. It takes you about three or four minutes to fill out and then you'll get a score and that score will tell you, in fact we really use in sleep science five categories, extreme morning type, morning type, neutral, evening type, extreme evening type and it will kind of bucket you into one of these flavors The other way you could really do it though, which is kind of like my quick rule of thumb It's just a rule of thumb. Sorry a rule Let me ask you the following question if you're on a desert island

Nothing to wake up for no pressures. No one to wake up for no work What time do you think you would like to go to bed and what time do you think you would like to wake up? The answer to that question is usually very different than currently when you have to go to bed and when you have to wake up. That mismatch is the misalignment between how you are forced to sleep versus how you are biologically designed to sleep. So that's another way that you can sort of answer the question.

And it's relevant, by the way, some people come to me and say, I've got vicious insomnia, I get into bed and I cannot fall asleep for the first hour or hour and a half. And then we go through this exercise of figuring out their chronotype. And what you realize is that they're going to bed at 10 PM because they have to wake up at six to go to work. And in fact, they're much more of an evening type. They would normally like to go to bed at maybe 12, 12, 30.

And so they don't necessarily have insomnia. They have this mismatch between their chronotype. And when they start sleeping a little bit closer to their natural sweet spot, they sleep better. So it is relevant to know your grown type. Yeah, and then other than that, I would just probably quickly go through a few others. Keeping your bedroom cool. Aim for around about 65 to 67 degrees Fahrenheit or around about, what is that, 18, 18.4 ish degrees Celsius. I know it sounds cold, but cold it must be.

You can keep your feet warm, hot water bottle, socks, that's fine, but the ambient must be cold. And that's colder than many people keep their rooms today, right? It is, yeah. Most people will come home, they'll set, have this ambient temperature of 70, 72 degrees in their house, and then they leave

that same thermostat setting for the night, and we need to cool down at night. Keep temperature in mind. Light is another thing. We are a dark deprived society in our modern era, and we need darkness at night to trigger the release of a sleep hormone called melatonin. As a tip, I don't like the word hack, but as a tip, try doing the following experiment. In the last hour before your bed, set an alarm on your phone or on your home device, say, set alarm for whatever time it is now before bed.

In that last hour, dim down half of the lights, even more of the lights if you can, dim down half of the lights in all of your house. And you will be surprised at how sleepy that increased darkness will make you feel. And what that tells you is that normally you are suppressing the release of this sleepiness hormone melatonin,

or it's a sleep timing hormone really, when you are bathed in electric light at night. So light is another one. The final two things I would mention, alcohol and caffeine, I know, I know, I'm sorry, this is bad news. Yeah, you're a bit depressing on this one, Matt, I have to say, but I think you should tell everybody so that they get all the facts.

Well, I'm much more bullish now. You know, some people sometimes on different podcasts when I'm interviewed will say, you know, what have you changed your mind on in the last five years? I've changed my tune on coffee. I would say drink coffee because the health benefits that have been associated with coffee are profound and very reliable. But here when it comes to sleep, the dose and the timing make the poison.

By the way, the reason that coffee is associated with health benefits has nothing to do with the caffeine. The reason is because the coffee bean contains a whopping dose of antioxidants. And because most people, and you know this better than most of us, Jonathan, most people in the Western world are deficient in their dietary intake. And the way that most people get their daily dose of antioxidants is through their cups of coffee. And that's why coffee is associated with health benefits.

Case in point, you get very similar health benefits for decaffe of coffee. And that's why coffee is associated with health benefits. Case in point, you get very similar health benefits for decaffeinated coffee. So it's not the caffeine, it's the coffee bean itself. But I would say the dose and the timing make the poison. Try to limit yourself to two cups on average, maybe three, but the critical thing is cut yourself off at least 12 hours before you expect to go to bed.

That's a good rule of thumb. And I would say just on that one, I'm actually more of a tea addict than coffee, but I have definitely discovered that this timing with the caffeine is important and I now cut myself off. I think this is something you can sort of figure out for yourself, Matt, a bit, right? Because there's a lot of personal variation in caffeine response, isn't there? Yeah, there is. And we know the genes that change the clearance, the speed of clearance caffeine. But in my case, that means I need to stop by about two or three o'clock in the afternoon. And if I go later, then sure enough, you know, it affects my sleep.

And sometimes also it can even mean you wake up again, right in the night, and then you can't go back to sleep. So it's a bit more complicated than I had imagined. Yeah, both make it harder to fall asleep, then it fragments your sleep. But the other thing that's pernicious about caffeine, some people will say, look, I'm one of those individuals, and they could be because they clear caffeine very quickly, but not quick enough, as we'll see.

They'll say, I can have an espresso with dinner, and I fall asleep, and I stay stay asleep and I'm just fine. Even if that's true, caffeine can actually decrease the amount of deep sleep that you have by somewhere between 12-15 percent. It depends on the dose of caffeine. We've done this in our laboratory. Now, to reduce your deep sleep by 15 percent,

I would have to age you by about 10 to 12 years, or you can just do it every night with an espresso. So it is a little bit, be thoughtful. And what about alcohol? Yeah, many people when they're struggling with sleep will turn to alcohol as a quote unquote sleep aid. Unfortunately, it is anything but a sleep aid. Alcohol is in a class of drugs that we call the sedatives

and sedation is not sleep. So when you have a couple of night caps, people say like, I always fall asleep faster if I've had a few drinks in the evening. You're not really falling asleep faster, you're just losing consciousness more quickly. That's the first problem, alcohol is a sedative. The second is that alcohol will fragment your sleep, like caffeine but through a different

chemical mechanism. You wake up many more times throughout the night, but the problem is you typically don't remember those awakenings. The next morning you wake up, you feel unrestored and unrefresheded but you don't remember waking up and so you don't put two and two together. The final reason that alcohol is not great for your sleep is that it is quite potent at suppressing your REM sleep or your dream sleep and we know that dream sleep as we've spoken about it has lots of benefits of the brain. It's critical for the body too. REM sleep is the peak time during the 24-hour period when

men and women release their peak levels of testosterone, for example. So we need REM sleep. So I'm very nervous as a scientist to tell anyone how to live their life. I don't think I have any business doing that. What I'm here to do as a scientist is simply impart the knowledge so that you can then make an informed choice as to how you want to live your life. And of course, my goodness, when it comes to cups of coffee and having a drink now and again, life is to be lived for goodness sake. So don't get puritanical about it. But just

know the evidence and know that there can be consequences. By the way, I would say that with alcohol, the politically incorrect advice that I would never offer you would be go to the pub in the morning and that way the alcohol is out your system by the evening and then you'll be just fine. But I would never say such a thing on a health podcast. We did a whole podcast on alcohol and I think it's a very interesting topic, but I think the impact on sleep is clearly one of the big downsides. And Matt, one thing that you haven't mentioned, but it was so influential on me, was about making your room like a cave so you don't get woken up in the morning.

Is that something that still you believe is really important? Yeah, very much. So this is temperature. So it's not just about temperature, but it also combines the third tip I mentioned, which is darkness. So keeping your bedroom cool and dark. And then if you need to,

you can use earplugs or a sound machine. We don't know too much about sound machines, whether they're helpful or hurtful to sleep right now, I think for the most part, that they seem to be mostly benign. Just before we wrap it up, I think one thing I realize you haven't mentioned is screens and that comes up quite a lot. Yeah, yeah, it's a good question. You know, this comes to the light issue again, particularly light exposure at night, and unfortunately our screens are enriched in the blue LED light spectrum, which is the

worst for our melatonin levels. It suppresses it most powerfully. I would say that in probably over 50 to 60% of the studies looking at blue light screens, they have an impact on sleep, but some of them have not found a robust effect. What we do now know is that those devices, perhaps the greater detrimental impact on sleep is not necessarily the light, but they're activating engagement.

Because when you are on these devices, particularly your phone, it is designed to capture your attention, make you alert, and keep you awake and sustained and engaged. Many people will be what we call sleep procrastinating, where they are perfectly tired, but they're so engaged with their device that they can't put it down. That seems to be, if anything, it's this alertness that actually masks otherwise very strong sleepiness.

So my rule of thumb, again, not to get puritanical, that genie of technology is out of the bottle and it's not going back in anytime soon, no matter what I say. So use your phones and your screens. Just keep in mind that they can have an impact on your sleep. The rule of thumb, I much prefer people to keep their phones out of their bedroom. If you absolutely have to take it into the bedroom, here's the rule. You can only use it in the bedroom standing up. I hadn't heard that one before.

It's really interesting. You kind of think, okay, after about five or six minutes, I'm just going to sit down on the bed. No, at that point, that's the rule. You're done. Put the phone away. I'm just going to sit down on the bed. No, at that point, that's the rule. You're done.

Put the phone away. I hope you found the information in this week's episode useful. If you're interested in improving your gut health, you might want to download our free gut guide. It's packed with recipes and science-backed information to help you on your journey towards better health. Go to zoe.com slash gut guide to download it for free.

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