ZOE Science & Nutrition - Most replayed moment: How to Balance Sunlight and Suncream | Professor John McGrath

Episode Date: June 9, 2026

Today we’re talking about skin and sunlight. Skin and sunlight have a complicated relationship. Sunlight helps our bodies produce vitamin D, which is essential for overall health. However, too much exposure can accelerate skin ageing and increase the risk of skin cancer. So how much sun is enough? Are most of us getting too little, or too much? And where does sunscreen fit into a healthy daily routine? I’m joined by Professor John McGrath to explore how sunlight affects our skin, and how to strike the perfect balance 🌱 Try our science-backed and tasty wholefood supplement Daily 30+ Get our brand-new app and Gut Health Test designed by world-leading gut health and nutrition scientists to build healthy eating habits 👉 Join ZOE Follow ZOE on Instagram.📚Books by our ZOE Scientists The Food For Life Cookbook Every Body Should Know This by Dr Federica Amati Food For Life by Prof. Tim Spector Ferment by Prof. Tim Spector Free resources from ZOE Eating for Better Brain Health: Your brain-gut blueprint How to eat in 2026 - Discover ZOE’s 8 nutrition principles for long-term health Live Healthier: Top 10 Tips From ZOE Science & Nutrition Gut Guide - For a Healthier Microbiome in Weeks  Better Breakfast Guide 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 Zoe 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 skin and sunlight. Skin and sunlight have a complicated relationship. Sunlight helps our bodies produce vitamin D, which is essential for overall health. However, too much exposure can accelerate skin aging and increase the risk of skin cancer. So how much sun is enough? Are most of us getting too little or too much? And where does sunscreen fit into a healthy daily routine?

I'm joined by Professor John McGrath to explore how sunlight affects our skin and how to strike the perfect balance. What's actually happening on the surface of my skin every day? Well, this amazing organ that you have, the skin, you know, as an adult, you've got 1.8 square metres of amazing carpet, which we recognise as this barrier that keeps the outside out and the inside in and also has its own appearances, too. It's a very dynamic structure. You know, the outer layer of your skin is replacing itself every four weeks in reaction to the external environment. You really have to build up this barrier to protect yourself. And it's rather amazing what skin can do in terms of its function. You know, it's there, not only to look nice, but it also protects you. It protects you against inflammation,

against infection. It makes hormones. It makes vitamins. It has its own immune system. It's a fabulous organ and so it's worth thinking about and worth preserving. And of course over the course of our lifetime, it does change a little bit and sometimes it doesn't always work as well as it did in earlier life. But that's part of a natural process for this amazing organ, our skin. What happens when sunlight hits our skin? So sunlight, as we know, is composed of lots of different wavelengths and these will penetrate the skin. Many of your listeners will have heard of UVA, UVB, UVC, visible light, and all of these will have different penetration capabilities through your skin. But ultimately what they're doing is either causing damage to your genetic material,

the DNA, or directly some of the structures and fibers in your skin. So it is an enemy on one level, but actually in moderation, sunlight is good for you. There have been many epidemiological studies that shows sunlight is really good for your heart. So cardiovascular health can be improved by sunlight exposure. So that probably means next time you're not in the gym and you're lying on the beach and somebody phones you up and you say, just doing a bit of cardio. It actually may be telling the truth.

So dermatologists are always worried about DNA damage, about cancer, about molds turning malignant, what we call melanoma and some other skin cancers. but there are other clinical and human health issues that are beneficial. We all feel good, of course, because of the endorphins that sunlight releases into our skin. I was actually going to ask, John, could you explain for a minute, how can sunlight be good for my heart? And in fact, then I'd love you to explain how sunlight can make me feel good, because it definitely does. What's going on?

So let's take the skin part first of all. So when you shine sunlight on your skin, it is damaging the DNA in your skin. So tanning, I prefer the word DNA damaging. So you're actually damaging the DNA. But when you have damaged DNA, it will produce a chemical, which we call POMC, pro-opiomelanacortin. And pro-opiomelanacortin, POMC, is then broken down into various other subchemicals, some of which will stimulate the suntan, something called alpha melanocyte stimulating hormone. but one of the other breakdown products of POMC, believe it or not, is beta endorphins. So everybody knows about endorphins being a sort of stimulus to making us feel good, to feel better.

Exercise can stimulate endorphins. Other things can stimulate your endorphins. Sunlight can stimulate beta endorphin in the skin. And maybe this is one reason why people like lying in the sun or going to tanning salons because you're becoming almost a natural junkie with your endorphin release in the skin. And so that's why we feel good, to some extent. In terms of your cardiovascular health, it's the chemistry and the science is much more deep than that. You're controlling inflammatory chemicals called nitric oxide and other destructive anti-oxidant quenching as well can be useful.

We don't know it for sure, but from population studies, we know it's good for your heart. can save a lot of lives from cardiac ill health by having sun exposure. Do we understand how the sunlight is contributing to my heart health? Is it as simple as just I definitely feel much happier on the days when the sun is shining and somehow I'm just overall, you know, it's reducing my stress or is there something else going on? There's going to be some science there. I think this simple way to think about sunlight is you have this double-edged sword.

You have, when sunlight gets shined on your skin, it quenches various toxic chemicals that could be destructive to your general health, including your heart. So you have the benefits of quenching those damaging chemicals. Offset against that is the DNA damage in your skin, which could promote the acceleration and development of skin cancer. So that's kind of the double-edged sword of sunlight, I think. It's really interesting. So there's a sort of balancing act here, potentially some of the messaging we've all been getting for the last 30 years of like all sun is dangerous because you're going to get skin cancer.

There's also you're losing out on some benefits, which you're talking about for heart health, for our mood, all the rest of it. And so is it possible to have a middle ground? Is it possible to have a situation where you shouldn't be avoiding sun all the time? That would be my recommendation. It's a question of just where you set that line and it will vary from person to person. But I think an important message is that some sunlight is good for most people. And when you look around what most people might be doing in the Western world, whether that's the States or the UK or France or whatever, are most people protecting their skin enough from your

perspective too much or not enough? If I put my dermatologist hat on, I would say probably not enough because it's really just the start of education for people, I think, in terms of how to look after your skin. People have been aware of this, you know, since the rising incidence of skin cancer in the 1960s and 70s, people really started to understand that the sun wasn't always our friend, particularly when it was taken in excess. And gradually, different parts of the population around the world are getting the message. It seems that older men are still slow. to get the message about protecting your skin health,

but in some countries around the world, New Zealand, Australia, the message has been there for 40 years plus, and people are sensible, take action, know what to do in terms of good behavior and bad behavior. And I think it's important to keep the message going, that there are things we can do to look after our skin, to protect our skin, to reduce the incidence of aging and skin cancer.

But at the same time, all of us need to enjoy a bit of sun every now and again. Should there be a daily skincare routine? And if so, what really should be in it? There is such thing as a good skincare regime. And it's typically divided up into three bits. And most dermatologists will give similar advice. The first one is about cleansing and what sort of thing you do to cleanse. And there are a whole range of cleansers out there. For those of us who are quite naive on this, what do I need the cleanser for? Well, just to get rid of any dirt and grit and dead skin on the surface that you may have accumulated over the previous few hours, it just, removes some of the products there. I think most people will just probably use something in the shower

or quick wash in the basin, but that still constitutes cleansing to some extent. But there are a number of products which are out there as cleanses. But you're not sitting here saying, oh, that's all a bad idea. I'm stripping my skin of what you shouldn't do. Actually, cleansing gets the thumbs up. Cleansing of some sort is probably a good idea for most people. And then the second stage after that is around moisturising. And this is, again, a little bit contentious because some people just don't need a moisturiser, but probably about two-thirds of the population would benefit from putting a moisturiser onto their skin. Choose one that's more creamy, perhaps, than greasy, particularly if you have a spot or acety-prone skin. Grease can make things worse, and nobody wants to look

ultra-shiny after putting that on. But some moisturiser may be helpful after that cleansing, particularly as the cleanser may dry the skin to some extent. And John, what does a moisturiser do? So it's just providing some hydration to the superficial part of the skin. Again, it's not penetrating. It is just providing you with some lipids or some other related moisture retaining compounds on the surface to improve your appearances of your skin, to maybe reduce the amount of water loss that naturally occurs through your skin, and to deal with any dryness that might be there. So it can be a good idea, and it's a very personal choice about what moisturiser you use. And sometimes some of the cheaper products are just as good

as some of the more expensive ones. So moisturized would be phase two. And then the next phase, I think that dermatologists will lobby hard about is the sunscreen. And it is a good idea to put sunscreen on. How to do it? What to choose?

These can be personal choices. But most dermatologists would recommend you don't use a sunscreen with a low sun protection factor. 30 plus is the minimum that most dermatologists would recommend, sometimes 50 plus. When you look at the label on it, look for something that gives ultraviolet A, UVA protection as well. And on most sunscreen products, there's a little logo.

It says UVA in a circle, and that's so something to look at. So you're looking for something, Factor 30 plus, with a UVA logo on. And then it's important to think, how much do I actually put on? Well, if you're putting on your entire body, obviously most people won't be doing that because they'll be dressed and ready to go. But if you were to cover your entire 1.8 square meters of adult skin... So that's like 10, 12 square feet? Yes, it would be quite a lot, wouldn't it really?

Then you would need at least six teaspoons worth of sunscreen. Another analogy people sometimes think is a shot glass full of sunscreen. That would be enough for one application of sunscreen. Which is quite a lot of sunscreen, isn't it? Yes, because I think one of the big problems we have, have, you look at something it says SPF 30, SPF 50, or something like that. But actually, how those numbers were calculated is quite different from what we do in practice. So those SPF numbers were calculated in laboratory by putting a certain amount of sunscreen onto a square centimeter or quarter inch of

skin and shining light on it and then generating numbers and showing what an SPF can mean in the lab. But actually, none of us, myself included, ever put sunscreen on as thickly as it was done in those laboratory calculations. Is that right? It's like put on really thick to show you that it works really well. And then in reality, we just put it like a little dab on. It's a standardized laboratory approach. But we actually just dab and smear, don't we really? And that comes on to the next point of sunscreen application is that you should really try and think about putting it on repeatedly throughout the day. Every two to three hours is a good idea. So once before you dash out of the house is not enough.

Every two to three hours you should be thinking about putting your sunscreen on. And that is a good regimen. Cleanse, moisturise, sunscreen, and you're done. Can I ask about the sunscreen a little bit more? Because you just talked also about the balancing factors between the risk of cancer on one side and some of these other benefits. So maybe my first question is, is the only... benefit of sunscreen to avoid the risk of cancer, or does it also help against the sort of

some of the skin aging that you've been talking about previously? Both. So sunscreens will protect you against both aspects of that type of problem. So the aging aspects and also the malignancy, the cancer risk that everybody can experience with sun exposure. So a double hit. I'll end this episode with something I think you'll like, a free Zoe gut health guide. If you're a regular listener, you know just how important it is to take care of your gut.

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To get your free Zoe gut health guide, head on over to zoey.com slash gut guide. Thanks for tuning in and see you next time.