Most replayed moment: How to Balance Sunlight and Suncream | Professor John McGrath

Summary

Podcast Summary: "How to Balance Sunlight and Suncream"

Podcast: ZOE Science & Nutrition
Episode: Most replayed moment: How to Balance Sunlight and Suncream | Professor John McGrath
Host: Jonathan Wolf (ZOE)
Guest: Professor John McGrath
Release Date: June 9, 2026

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Episode Overview

This episode of ZOE Science & Nutrition, hosted by Jonathan Wolf, dives into the nuanced relationship between sunlight and skin health. Professor John McGrath—expert dermatologist—explains the science behind sunlight's dual effects: its necessity for vitamin D and cardiovascular and mental health, as well as its role as a major risk factor for skin aging and cancer. The conversation covers how sunlight interacts with the skin, debates around sun avoidance, and practical advice for balancing sun exposure while protecting against harm with sunscreen and daily skincare routines.

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Key Discussion Points & Insights

1. The Skin: An Overview

• [00:49] Professor McGrath describes the skin as a remarkable, dynamic organ approximately 1.8 square meters in adults, serving as a barrier and active participant in immunity, hormone, and vitamin production.
  • Quote: “You’ve got 1.8 square meters of amazing carpet, which we recognize as this barrier that keeps the outside out and the inside in... It has its own immune system. It’s a fabulous organ.” — Prof. John McGrath [00:49]

2. How Sunlight Affects the Skin

• [01:52] Sunlight contains multiple wavelengths—UVA, UVB, UVC—that penetrate the skin to different degrees.
• Main Effects:
  • Can cause DNA damage, potentially resulting in skin cancers (melanoma and others).
  • In moderation, sunlight offers broad health benefits, including improved cardiovascular health and mood elevation due to endorphin release.
  • Quote: “It is an enemy on one level, but actually, in moderation, sunlight is good for you.” — Prof. John McGrath [01:57]
  • Memorable moment: Cardiovascular health can be boosted by sunlight: “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.” — Prof. John McGrath [02:19]

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3. Sunlight and Heart Health

• [03:22] Sunlight triggers release of pro-opiomelanocortin (POMC) in skin, resulting in:
  • Alpha-melanocyte stimulating hormone (for suntan)
  • Beta-endorphins (“feel good” chemicals, releasing the same as exercise)
• Cardiovascular Mechanisms:
  • Sunlight may lower toxic inflammatory chemicals like nitric oxide.
  • Epidemiological evidence suggests lower cardiac mortality with sensible sun exposure.
  • Quote: “When sunlight gets shined on your skin, it quenches various toxic chemicals that could be destructive to your general health, including your heart... You can save a lot of lives from cardiac ill health by having sun exposure.” — Prof. John McGrath [05:17]

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4. The Double-edged Sword of Sunlight

• [05:52] Sunlight is beneficial and risky:
  • Benefits: Improved cardiovascular health and mood.
  • Risks: DNA damage, skin aging, and potential for cancers.
  • The public health message should not be “all sun is bad”; moderation and balancing individual needs is key.
  • Quote: “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.” — Prof. John McGrath [06:15]

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5. Public Attitudes and Sun Protection

• [06:26] Many people in Western countries still aren’t protecting their skin adequately, especially older men. However, regions like Australia and New Zealand have longstanding sun safety cultures.
  • Continuous public education remains vital.
  • Quote: “People have been aware of this, you know, since the rising incidence of skin cancer in the 1960s and ’70s... In some countries around the world, New Zealand, Australia, the message’s been there for 40 years plus.”— Prof. John McGrath [06:42]

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6. The Ideal Daily Skincare Routine

• [07:53] The dermatologist-recommended three-step routine:
  1. Cleansing: Removes dirt, dead skin, sweat (can be as simple as a quick shower wash) [08:11–08:37].
     • Quote: “Cleansing of some sort is probably a good idea for most people.” — Prof. John McGrath [08:37]
  2. Moisturizing: Hydrates and protects the skin surface, reduces water loss. Especially useful for about two-thirds of people; personal product choice matters [08:37–09:16].
     • Quote: “Some moisturiser may be helpful after that cleansing... particularly as the cleanser may dry the skin to some extent.” — Prof. John McGrath [08:37]
  3. Sunscreen: Critical for protecting against aging and cancer [09:16–12:29].
     • Dermatologists recommend SPF 30 or higher with UVA protection (look for the UVA-in-circle logo).
     • Amount: Six teaspoons or a shot-glass for full body (most use less).
     • Frequent reapplication—every 2–3 hours—is ideal.
     • Quote: “Most dermatologists would recommend you don’t use a sunscreen with a low sun protection factor. 30 plus is the minimum.” — Prof. John McGrath [09:39]
     • Quote: “Every two to three hours, you should be thinking about putting your sunscreen on.” — Prof. John McGrath [11:57]

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7. Sunscreen: Dual Benefits

• [12:50] Sunscreen not only prevents cancer risk, but also shields against premature skin aging.
  • Quote: “Sunscreens will protect you against both aspects of that type of problem. So the aging aspects and also the malignancy, the cancer risk...” — Prof. John McGrath [12:50]

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Notable Quotes & Memorable Moments

• On why sun feels good:

  • “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.” — Prof. John McGrath [03:22]

• On the skin’s self-renewal:

  • “The outer layer of your skin is replacing itself every four weeks in reaction to the external environment.” — Prof. John McGrath [00:49]

• On sunscreen use in reality:

  • “None of us, myself included, ever put sunscreen on as thickly as it was done in those laboratory calculations.” — Prof. John McGrath [11:53]

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Timestamps for Key Segments

• 00:49 — Functions and adaptability of skin
• 01:52 — Sunlight’s multiple effects: risks, benefits, endorphins
• 03:12 — Sun and heart health explained
• 05:17 — The balance between benefit (heart) and risk (cancer)
• 06:15 — How much sun is enough? Personalizing sun exposure
• 06:26 — Are people protecting their skin enough?
• 07:53 — Three-step skincare routine
• 09:39 — Choosing the right sunscreen
• 11:57 — Reapplying sunscreen: why and how often
• 12:50 — Sunscreen prevents both cancer and visible aging

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Summary Takeaways

• Some sunlight is essential for vitamin D production, cardiovascular wellbeing, and mood, but UV exposure must be balanced against the very real risk of skin damage and cancers.
• Personalizing sun exposure based on skin type, lifestyle, and geographic region is vital.
• Daily skincare matters: Cleanse, moisturize (if needed), and always use SPF 30+ sunscreen with UVA protection, reapplying every 2–3 hours while exposed.
• Routine and awareness are key in enjoying the sun’s benefits while minimizing harm for lifelong skin and overall health.

Transcript

[A]

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. 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.

[B]

What's actually happening on the surface of my skin every day?

[C]

Well, this amazing organ that you have, the skin, you know, as an adult, you've got 1.8 square meters of amazing carpet, which we recognize 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.

[B]

What happens when sunlight hits our skin?

[C]

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 show 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 moles 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.

[B]

I was actually gonna 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. It definitely does. What's going on?

[C]

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. When you have damaged DNA, it will produce a chemical which we call POMC, pro opiomelanocortin and pro opiomelanocortIn. POMC is then broken down into various other sub chemicals, 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. You can save a lot of lives from cardiac ill health by having sun exposure.

[B]

Do we understand how the sunlight is contributing to my heart health? I mean, 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?

[C]

There's going to be some science there. I think the 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.

[B]

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 we're talking about for heart health, for our mood or the rest of it. And so is it possible to have a middle ground? Is possible to have a situation where you shouldn't be avoiding sun all the time?

[C]

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.

[B]

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?

[C]

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 you know, 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.

[B]

Should there be a daily skincare routine and if so, what really should be in it?

[C]

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, what sort of thing you do to cleanse. And there are a whole range of cleansers out there for Those of us

[B]

who are quite naive on this. What do I need a cleanser for?

[C]

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 cleansing.

[B]

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.

[C]

Cleansing of some sort is probably a good idea for most people. And then the second stage after that is around moisturizing. And this is again a little bit contentious because some people just don't need a moisturizer. But probably about 2/3 of the population would benefit from putting a moisturizer onto their skin. Choose one that's more creamy perhaps than greasy, particularly if you have spot or acne 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.

[B]

And John, what does a moisturiser do?

[C]

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 moisturizer 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 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 1.88 square meters of adult skin,

[B]

well, so that's like 10, 12 square feet.

[C]

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

[B]

of sunscreen, isn't it?

[C]

Yes, because I think one of the big problems we 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 the 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?

[B]

It's like put on really thick to show you that it works really well. And then in reality, we just put

[C]

like a little standardized laboratory approach, but we actually just dab and smear, don't we, really? And that comes onto. 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, moisturize sunscreen, and you're done.

[B]

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?

[C]

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.

[A]

As you can imagine hosting this podcast, running Zoe, juggling family life it all keeps me pretty busy, so I try as best I can to stay energized and show up well in all those parts of my life by fueling my body with the right food, by exercising, and by adding a scoop of daily 30 to my meals every day. If you haven't heard of Daily 30 yet, it's the gut supplement designed by our gut health scientists here at Zoe. It's made of over 30 high quality hand picked plants including seaweed, fungi and different types of fiber. Better yet, it contains ingredients that support gut health, digestion and energy, which is ideal for packed calendars and busy lives. Simply add one scoop a day to any meal for an extra boost of fiber and plant diversity. And because it tastes delicious on just about anything and adds a satisfying crunch, it quite quickly slots into your life, becoming a daily healthy habit you'll always have time for. By the way, whenever we talk about

[B]

Daily 30 as a good source of

[A]

fiber, we're required to say that it contains 4 grams of total fat per serving. Obviously that's all amazing healthy fats from plants, so order yours [e-mail] daily30. Thanks for listening and see you next time.