Skeptic Check: Sunny Daze

The anti-sunscreen social media trend

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1:13That is the theme, I think, that we come back to over and over again with these claims, is that these products are toxic, that the chemicals in them may potentially do more harm than good. An online anti-sunscreen movement is making real-world impact on how people protect themselves from the sun. Meanwhile, surprising new research about the health benefits of sunshine has come to light. People who are exposed to less overall light tend to have higher rates of most of the main cardiovascular diseases

1:48and also higher rates of many cancers. But as we know, UV rays can lead to skin cancer. So how much sun should we get? Welcome to Big Picture Science. I'm Molly Bentley. In this episode of our regular look at critical thinking, we shed light on the claims that sunscreen is toxic and sunlight can be good for you. This episode is so bright, you'll have to wear shades. It's Skeptic Check Sunny Days.

Men's Health investigation into influencers

2:13It was a reporter who drew our attention to the online trend of rejecting sunscreen. My name is Brian Underwood. I'm the Beauty and Grooming Director at Men's Health and Women's Health. As someone who regularly covers beauty and skin care topics, Brian has been aware of anti-sunscreen advocates for years, but he had waved them away like flies on a beach.

2:45You know, some of these sort of anti-sunscreen, sunscreen skeptic posts did pop up in my feed and I thought, hmm, that's interesting. But I honestly, you know, I didn't take it very seriously. I just thought it was, you know, some content creators trying to say the most outrageous thing they can for engagement. I'm not a big sunscreen guy because most of them are just chemicals you spray on your skin that actually causes skin cancer and messes up your hormones. And then, you know, I was having lunch with some friends from the Skin Cancer Foundation,

3:16a pretty prominent nonprofit here in New York City, who told me that they were actually considering petitioning the NIH to act, to stop the spread of misinformation about sunscreen and tanning on social media. They were going to have about 100, I believe, prominent dermatologists sign this letter. And it really got me to thinking if an organization like this is taking this topic seriously, it's obviously having an effect and it is obviously penetrating the consumer mindset.

3:51And I thought, you know, maybe there's a story there for us to do. And as I looked into it more, there certainly was. And the reason it ended up in men's health is because what I discovered when I was looking through these posts was that a lot of them are created by men. And I think it's the sort of health maxer, optimizer kind of male culture on social media that sort of feeds into this a bit. And so that's how the piece wound up in men's health.

4:23The anti-sunscreen movement is coming for you, is his article that describes the growing online movement, the science it ignores, and the role that the FDA may have played in confusing members of the public about the safety of sunscreen. Brian says that the lack of clarity turned up the heat on the anti-sunscreen movement. You know, one of the first and most arresting images I came across was of a creator who had taken a bottle of Banana Boat sunscreen, I believe it was,

4:53you know, sprayed it and lit the spray on fire with a lighter. And obviously that's all to say, in his view, look at this toxic, look at these toxic chemicals that you're spraying onto your skin. They're flammable, for goodness sake. According to the National Cancer Institute, since the introduction of sunscreen in 1940, melanoma has increased by over 200 percent. Brian Underwood says that while some influencer antics are outrageous, anti-sunscreen proponents are united in their claim that sunscreen is harmful to your health.

5:30And that is the theme, I think, that we come back to over and over again with these claims, is that these products are toxic, that the chemicals in them may potentially do more harm than good. And then some of them even go as far to say that sunscreen could be behind the rising rates of skin cancer in the United States, which we do know are going up, especially in young people, and that we've been using sunscreen and skin cancer rates are continuing to climb.

6:04So perhaps it's sunscreen's fault. Those are the two biggest themes, I would say. Right. The classic confusion, perhaps, between correlation and causation. Well, Brian, let's look at the evidence that people are being swayed by these influencers. So there are a number of people out there on social media that are saying that sunscreen is toxic, that you shouldn't use it. Their claims are one thing. You know, whether or not that is swaying the public is another. And you include the results of a survey in 2024 that the Orlando Health Center Institute put out that one in seven adults under the age of 35 now believes that daily sunscreen use is more harmful to the skin than direct sun exposure.

6:50Can we link those two facts, the influencers and those under 35 that are saying, nope, sunscreen's not for me? Well, it's an interesting point. So in 2024, when that survey came out, I'm not sure that we could link them. It made sense, of course, because that's where a majority of people, especially young people, are getting their information these days is on social media. However, I think the more interesting, not more interesting, but equally as interesting data is the American Academy of Dermatology.

7:24They do an annual sun safety survey. And this year, the 2026 survey found that a fairly significant percentage of people have reported stopping, discontinuing their use of sunscreens due to safety concerns they saw on social media. So I think there is the direct link between people's sun protection habits and what they're seeing on social media in terms of how they protect themselves or don't protect themselves from UV damage.

Chemical and mineral sunscreen filters

7:54When we get into the claims of the toxicity of these ingredients, it's not just that they're flammable. I don't think that's the number one fear that people have, although that would be a scary one if you're swayed by that argument. But it has to do with some of the chemicals, these filters. There's organic and inorganic filters. Brian, could you walk us through that? What are filters? What are the role that they play in sunscreens and what are some of the concerns that some members of the public are believing about them? Yeah, so sunscreens are very unique in terms of skincare products that you can buy at your local drugstore or on Amazon in that they are regulated by the Food and Drug Administration as over-the-counter medications.

8:35So as a result, the active ingredients in those products are subjected to certain testing protocols and the percentages are also regulated by the FDA. They have to be listed on the label under active ingredients in certain percentages. And those ingredients are broken down into two categories, as you mentioned, organic or chemical filters and inorganic or mineral filters. So currently, the FDA has approved the use of 15 organic or chemical filters and two inorganic or mineral filters, which are zinc oxide and titanium dioxide.

9:13So some of the concern comes from the fact that in 2019, the FDA did a study that found that the organic or chemical filters were absorbed into the bloodstream at levels higher than what the FDA would like to have seen. And as a result, they categorized the sunscreen filters into two categories. One is category one, which is considered generally regarded as safe and effective or grays.

9:43And the second is category three, which is needs more safety data. And most of the chemical sunscreens fell into that category. The confusing part for people, of course, is that they're still available to be purchased here in the United States. So people were left saying, OK, the FDA needs more safety data on these ingredients, but I can still buy them at Walgreens. So why would I want to buy them if the FDA says we need more safety data? And I think that's where a lot of this confusion came from.

10:16And in fact, that 2019 absorption study and the resulting FDA categorization of those ingredients is really what a lot of these creators cite as evidence as to how and why these chemicals are toxic. Let's break down some of those terms and some of the specifics there. One is just the role of these filters themselves. You said that there can be up to 15 different ingredients. But Brian, are they all in one bottle of sunscreen or do different manufacturers use different chemicals?

10:46And what actually are they doing when it comes to those sun rays? Yeah, so it's usually a cocktail of ingredients. So what you'll normally find is a mix of the organic or chemical filters, different ones, maybe four to six of them. Sometimes they even do mix in some of the inorganic filters, the zinc and titanium, to create what's called a hybrid sunscreen. So it's a mix of organic and inorganic. And essentially what these ingredients do, and both categories of ingredients work in the same way, they absorb ultraviolet radiation, UVA and UVB light, and they convert it into harmless and negligible heat so that it doesn't harm your skin.

11:29Now, the inorganic or mineral filters, they do some refraction of light, but I think that's actually a misconception. I think a lot of people assume that when they put on a mineral like a zinc sunscreen, it's just reflecting all of the sun's rays. But that's not really how modern zinc formulas work. They also work primarily through absorption as well. And that's how they protect your skin from ultraviolet A and ultraviolet B radiation.

11:59And one of the clarification of terms, you gave two categories and you said one was grays and non-grays. And we should say that's G-R-A-S-E, not G-R-A-Y or G-R-E-Y-S. Just briefly, what does grays stand for? Yeah, so grays is the categorization that the FDA has used to classify the two forms of sunscreen ingredients. And you're correct, it's spelled G-R-A-S-E, and it stands for generally regarded as safe and effective.

12:30Brian, let's look at the role of the FDA in this, because you say that while it's tempting to dismiss these influencers as conspiracy theorists, in some cases, who are saying that sunscreens are actually being created so that incidence of skin cancer goes up, or at the very least of people who are cherry-picking the data, something that we understand in covering science is something that does not provide the full picture. But you also say that the FDA has a role to play in sending the public mixed messages, or at least not clarifying confusing messages about the safety of some of these ingredients.

13:03As you said, some of them maybe were not tested as much as they should be. That's a scary message for the public to absorb, or at least a confusing one. Certainly. And certainly when you have an agency like the FDA say, as I mentioned earlier, we need more safety data on these ingredients, but still buy them. You should still buy them. You should still use sunscreen. It's still available to you. You know, I think that that was, and a lot of the dermatologists that I spoke to for this story agree, that was a sort of unfortunate miscommunication on the part of the agency in this respect,

13:38because it really did leave people with an information vacuum that unfortunately was filled with some of the content that we are talking about now. The truth is, many, many, many of these organic or chemical filters that the FDA listed as Category 3 grays, meaning they need more data, have been used for decades overseas, have tons of safety data on them. And the FDA is just a little sluggish to accept that data in its own evaluation process.

14:10And now, look, we want federal agencies that take these things seriously, that are looking out for the best interests of, you know, the American citizen. So it's not a bad thing that they are asking for more and want more. But it certainly did leave people with a lot of questions. And, you know, what I would say to that is most of the studies, the absorption studies, use amounts that the average person would never be exposed to in real-life conditions.

14:41And so that's one really important thing that you need to keep in mind. The other thing is there has never been a well-designed human trial that has shown that any sunscreen ingredient causes harm to human health. That's another really important thing. Never. Just to bring up one other point that you cite as maybe not an inflection point, but something that happened that maybe added to this confusion was, or at least to this panic, is in 2021, certain sunscreen manufacturers actually recalled products that contained benzene.

15:15Yes. What was the story with that? And why did they do that? And then what was the fallout? Yeah. So this was mostly in regard to aerosol sunscreens. And obviously, benzene is a carcinogen. No one wants benzene in their products. And I don't think anyone believes that benzene was added to these products purposefully. No one believes that. What happened was there was a chemical reaction with the propellants in these aerosol products that created benzene as a byproduct. And once that was discovered,

15:46the manufacturers immediately recalled those products. And the issue has been as one of the dermatologists that I spoke to for the story said, the issue has been solved. She feels no qualms about recommending aerosol sunscreens to her patients. So, but again, it sort of is another piece of this puzzle that makes you think, can I trust these products? Oh my gosh, a cancer causing chemical in these products. And it's when you take it out of context like that, you can certainly see why people would be alarmed

16:20and why people would be primed for some of the messages that these anti-sunscreen creators have online saying, these products are toxic. And you can then get in the mind of the average person who maybe read a news article about these products being recalled and say, oh yeah, they are. I just saw that on the news. So it's sort of a vicious cycle. But again, I think it's important to keep in mind that this was not shown to have caused any harm to anyone and the issue was immediately addressed. You know what this is reminding me of as you outline this anti-sunscreen movement and how

16:56one study or one announcement suggesting that there's some concern with the sunscreen reminds me of the vaccine, the anti-vax movement. And then once the idea is out there, it is nearly impossible to bring that false idea back. And in the case of vaccines causing autism, a paper that was, you know, retracted a couple of decades ago. It's really interesting that you bring that point up because we do talk about that in the story, sort of the political climate that we're in now and how it may have contributed to just an overall

17:26skepticism of public health agencies and public health recommendations. And one of the creators that I spoke to for the story, who's kind of combating some of this bad information, she's Australian. She's done some incredible work. Her name's Dr. Michelle Wong. And she said that, you know, as an Australian, she looks at the United States and thinks that health information has become so politicized here in our country. And I do think you are right to point that out because it is something that I do believe has played a part, you know, a skepticism

18:00overall of public health. And I think that really started to foment during COVID, as you just mentioned, and vaccines. And now I think you're starting to see it in this conversation as well. Well, Brian Underwood, thank you so much for this discussion. Thank you so much for having me. Brian Underwood is beauty and grooming director of the magazine's Men's Health and Women's Health.

18:37Coming up, the anti-sunscreen movement may be ignoring decades of scientific evidence about skin protection. But are they basking in a ray of truth about sunlight itself? Some research suggests we shouldn't always dive for the shade.

Health benefits of ultraviolet rays

18:52It was like 20 minutes of average, typical summer sunshine on their arm was enough to lower their blood pressure like four to six points. Next, the health benefits of UV rays. This episode of our regular look at critical thinking on big picture science is skeptic check sunny days.

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19:59Here's a twist to the sunscreen debate. If we obsessively slap on sunscreen or confine ourselves to dark interiors, we might run into another problem, depriving ourselves of the health benefits of ultraviolet rays. An eye-opening study published a few years ago in the International Journal of Environmental Research and Public Health titled, Insufficient sun exposure has become a real health problem. Summarize the findings of researchers who posited that more than 820,000 deaths each year could be linked to a lack of sun exposure.

20:35That was a paper that was published by a group of scientists in a diverse range of fields, each calculating up in their own field, the potential lives that were being shortened by lack of exposure to sunlight. And what they're basing that on is evidence that people who are exposed to less overall light tend to have higher rates of most of the main cardiovascular diseases and also higher rates of many cancers and also respiratory diseases and autoimmune diseases,

21:06although those aren't as big causes of death. My name is Rowan Jacobson and I am a science writer and the author of In Defense of Sunlight. Our fireball in the sky, well, not literally fiery, as the sun's nuclear fusion of hydrogen into helium doesn't produce actual flames, is shooting radiation at us all the time. Now, humans have evolved to use those powerful rays to our advantage. And it's much more than the aha mood uplift we get when we step

21:37into sunlight. In his book, In Defense of Sunlight, Mr. Jacobson outlines how sunscreens have fallen short over the decades. Now, to absorb these facts, we need to refer to the sunscreen alphabet, specifically the letters A, B, and D. For many years, we were told, go ahead and enjoy a sunny day as long as you wear sunscreen that blocks UVB. Those are the rays that can give us a visible burn. Well, it sounded like good advice until we discovered that UVA rays are the ones linked to the deadliest form of skin cancer,

UVA rays and melanoma risk

22:13melanoma.

UVA rays and melanoma risk

22:14Yeah, it looks like we got that one wrong. And I was kind of a casualty of that era. Like, I grew up in Florida in the 80s and 90s. And it was only at some point in the 90s, they realized, like, oh, we got to block UVA, too. So then broad spectrum sunscreens started coming in that did a better job of blocking UVA, but not perfect. By blocking only UVB and not UVA, the SPF, that is sun protection factor in older sunscreens, provided a false sense of security.

22:43And, you know, the SPF 20 meant you could stay out 20 times as long without getting a sunburn. But that meant you were actually absorbing 20 times the amount of UVA if you were spending a full day on the beach. And another drawback. By shielding ourselves from the rays that turned us into lobsters, we were also inhibiting the production of an essential nutrient. Those old sunscreens back in the day, by blocking UVB, that blocked vitamin D production in the skin. Before these confusing messages about sunscreen lead to a mental block about how to have a healthy

23:17relationship with the sun, Mr. Jacobson presents the latest science about the health benefits of sunlight. And he told producer Brian Edwards that the intersection of physics and biology helps us understand exactly what happens when the sun hits our skin. UVB is the highest energy part of even the ultraviolet spectrum. So that's the one that everyone used to worry about, because when it hits a DNA molecule, it's got enough energy that it can actually mess up that molecule, cause some kinks in the molecule that shouldn't be there so that then you don't make proper proteins from that molecule or it doesn't

23:51replicate, can lead to mutations. So UVB is super high energy and that's why you worry about it, but also that energy is used to produce vitamin D in the skin as well. And probably those things go together. Vitamin D seems to be an anti-cancer molecule and biology figured out hundreds of millions of years ago that it could use that, that that energy was a problem and had to deal with, but it could use that energy to produce the solution to the problem. So the UVB is, you know, it's kind of high risk, high reward. And so that used to be the one that we worried about. And we thought, oh, that's the one that

24:24causes skin cancer. And the kind you create is a type of cancer called a squamous cell carcinoma. When you like, when you hear about how common skin cancer is, and it is very common, it's by far the most common type of cancer. What you're generally hearing about are the squamous cell carcinomas and basal cell carcinomas. Squamous cells and basal cells are responsible for about 98% of skin cancers, give or take. And very rarely do those lead to serious health concerns. Those are the ones that get cut out in dermatologist's office every day. And it's great that they do because they'll just

24:59keep getting bigger over time. So they can cause problems over long enough time, but they don't go invasive very often. Melanoma is the third and much rarer type of skin cancer. It's only maybe 2% of cases, but it's the one that is much more likely to go invasive. And it's the one that is responsible for the vast majority of skin cancer deaths. Still not a ton of deaths in the greater scheme of things, but that's definitely the one you want to worry about more. But Rowan, in the past 10 to 20 years, researchers have actually seen that it seems like it's UVA, not UVB, so closely tied

25:35to melanoma because those UVA waves, they're longer and they penetrate our skin more deeply. Why is that? And there's a bunch of reasons why we think that's true. One, the melanocytes that produce melanin that give our skins some darkness, but also turn cancerous and melanoma are located deeper in the skin. So UVB doesn't tend to penetrate deep enough to hit a melanocyte very often. Mostly what they're getting hit by is UVA, not with UVB. And it does it indirectly because it creates

26:06free radicals in the body, what are called reactive oxygen species. Basically, it energizes these molecules that then go around causing problems like grabbing electrons from other molecules. So it looks like UVA penetrates deeper into the skin, creates a bunch of free radicals that then end up harming melanocytes and trigger melanoma. The more sunlight you get, the higher your risk of getting a squamous cell carcinoma, it's definitely associated with UVB and cumulative effects. And it shows up on the parts of the body that get the most sunlight. So it makes total sense.

26:41Melanoma doesn't do any of those things. It shows up on parts of the body that get less sun exposure, usually like the trunk. It's not associated with cumulative or chronic sun exposure, not the everyday kind. It's higher in office workers than it is in outdoor workers. And it's most closely associated with a history of sunburns or with a pattern of intermittent sun exposure. So you say work in an office, you have skin that really has never seen the sun, and then you go on vacation somewhere

27:11super sunny, and you get burnt really badly. Or even if you use sunscreen, you're still you get a ton of solar radiation. That seems to be the pattern for melanoma. Like skin that has, you know, gotten some training, it's pretty good at dealing with small daily doses of this stuff. But skin that is really unprepared, and then just gets startled by a blast of radiation that it doesn't have the defenses for, that can lead to melanoma. Yeah, it's what you're saying, and from what I've understood from the book is, yeah, is that

27:43it turns out that some of our fear about sun, you know, may have inadvertently caused, you know, at least some people to avoid it, and then have these sun shocks, and and that could have worse effects for them, rather than, you know, them kind of getting that sun exposure to get some of the more positive effects that come from it. You'd mentioned vitamin D, which I think is the one that everybody, you know, I think has heard about. But there were still several parts that I think I didn't fully understand. Let's start with the fact that vitamin D should not be called a vitamin in the first place. Correct?

Vitamin D as a body hormone

28:13That's right. Because vitamins, in theory, are things that you can't make, that the body can't make, that you need in very small amounts from your your food supply. Vitamin D is actually a hormone that's produced in the body and the skin for free with sunlight. So it's, it's almost the opposite of the vitamin in that everybody can make all they need, getting the most easily acquired input in the world. But people by the by the Industrial Revolution, people were actually not making enough vitamin D, because suddenly human beings after hundreds of 1000s of years of

28:46being exposed to a lot of sunlight on a daily basis. They were living in, you know, tenement houses, they were working in factories. They were living in coal choked cities in the late 1800s. They were not getting any sunlight whatsoever, especially kids. So kids were coming down with rickets. And figuring out what was causing rickets led people to discover that there was this thing called vitamin D that you needed that would prevent rickets, and that the sun actually created it when it hit cholesterol molecules in the skin of animals. But then, you know, later on, in like the 1980s, some of these, you know,

29:22epidemiological studies observed that people who had naturally higher levels of vitamin D, which would have come from sun exposure, had lower rates of all those diseases we mentioned in the beginning, the cardiovascular diseases, diabetes, dementia, cancer. So, you know, maybe it made sense to assume, oh, vitamin D is responsible for all these things. This is a mistake we often make, though, in science, at least in the early days. So then we entered this era of supplementation, where it was like, okay, if most people have 20 nanograms per milliliter of vitamin D, but the

29:54people who have 40 nanograms per milliliter have really low rates of cancer and heart disease, let's get everyone up to 40 with pills. So a doctor started prescribing vitamin D supplements liberally. I think they're the most prescribed supplement in the world to this day. And then they did all these clinical trials just to confirm that raising everyone's D level artificially would result in lower levels of all these diseases, and they didn't. Like if you're deficient, like truly deficient, it definitely makes sense to take a supplement, just an insurance policy. But raising levels artificially beyond a normal level of like 20 nanograms per milliliter doesn't

30:30seem to affect health. But the people who naturally had high levels of D did have way better health. So was that because of the D they're making in their skin with sunlight was somehow different? Or was it just because D was a marker for sun exposure, and it was something else about sun exposure that was making those people healthy? And this is, I think, one of many processes that you lay out in your book that we have continued to learn is that there are different markers that I think that we've seen through time that have kind

31:02of led us to understand different aspects of how the sun is affecting our body. And another one is, I believe it's nitric oxide, which our bodies are kind of constantly excreting and have an interaction with the sun. I think nitric oxide is going to turn out to be a super important one, as important as D,

Sunlight and nitric oxide production

31:19probably. We just discovered it much later. Yeah, so nitric oxide, known for a long time that it's a very effective vasodilator in the body. It's a signaling molecule that's used for a bunch of different purposes, and it's naturally produced in the body in a couple of different ways. And when in blood vessels, it will cause the muscle to relax so that the blood vessel can dilate, and it'll reduce blood pressure. And it's actually used for a bunch of heart medicines, and by Agra, because of that. But we only discovered maybe 15 years ago, and almost

31:52accidentally, that it's also produced in the skin when sunlight hits skin. And it starts with nitrates, which are these compounds that we eat in our food. They're found in leafy green vegetables and root vegetables and things like that. And the body will actually stock the skin with these nitrates. And then when sunlight hits those compounds, it breaks them apart into nitric oxide, among other things. And then that nitric oxide diffuses through the body, and it seems to lower blood

32:23pressure. So there's been a couple of tests that have shown both in mice and grad students that if you shine light on them, their blood pressure goes down. And then there's also been observational studies that look at, you know, the whole population of the United States, or select groups of the United States, and compares how much environmental light exposure they're getting to their blood pressure. And there's a clear correlation where the more light you get where you live, the lower your blood pressure on average. And this is, you know, you've mentioned cardiovascular health, you know, several times throughout this,

32:54and this is the connection, correct? That, you know, essentially, by going out and spending time in the sun. And I think people can probably anecdotally, you know, kind of have experienced this at times that going out and kind of basking in the sun can have this kind of relaxing effect on you. And whether that's exactly the, you know, the lowering of the blood pressure itself, but you know, that is that is the effect that appears to be happening there. Yeah, it looks it looks quite solid. And I think there's probably multiple things happening. But yeah, I think the blood pressure is gonna be a big part of it. Because if you like in that study with the

33:26grad students, it was like 20 minutes of average, typical summer sunshine on their arm was enough to lower their blood pressure, like four to six points and keep it down for like an hour. So four to six point change in blood pressure globally would save millions of lives, which is I think, you know, you mentioned that paper at the beginning where the scientists were estimating that it was possible you could save as many as 820,000 lives a year. I think that's what they're getting at, like a part of that is just because you could reduce blood pressure globally just by telling

34:01people to go outside more. And so I think that kind of the last, you know, health benefit that you marked in the book that I want to visit is that I think about it, at least of kind of Victorian times of people who are sick and being told to go go out in the sun, like go get some fresh air, kind of the revitalizing power of the sun. But it turns out that there there is some strong evidence that sunlight also helps strengthen your immune system as well. Yeah, it has it has powerful effects on the immune system. And this is the part of the story that shocks a lot of people because they're like, why would sunlight affect the immune system? But this

34:35is actually the best known part of the story. It's just it was only known to a very small group of people who were doing this research. This field is called photoimmunology. And it goes back to the 70s. And started with skin cancer, they they found that like UV light, the wrong combination of UV light hitting skin could dampen the immune system and actually cause it to let a cancer slide, let it let a baby cancer slide by when it shouldn't have. So they realized that light could actually suppress the immune system. And that was like a shocker to everyone, because it didn't seem like something as

35:06ephemeral as light could do that. But the body was clearly responding in a purposeful way and in a way that had been set up by evolution to this light. Since then, we've learned that the entire immune system systemically through the whole body adjusts its behavior partly based on light. And it seems like there's a lot of things going on at once. But the way I kind of think of it in summary is that that light hitting the skin, it's a it's a mild stressor. It's a stressor in the same way that exercise is. And it triggers a response by the immune system to deal with the damage.

35:42But also part of what the immune system does is it sort of springs to life, deals with damage, but then it sort of assesses the damage and says, all right, we're good. We did it. No big deal. Don't freak out. You know, no, no, no over responses to this sort of daily garden variety insult. And it overall, it keeps the response mechanism at a comfortable, competent state. And this is we know

Sun exposure as an immune stressor

36:11this is exactly what happens with exercise. Exercise actually causes free radicals of DNA damage in the muscle cells and in the lung cells and triggers an immune response, an inflammatory response from the body. And then the inflammation fixes that damage. And then the other side of the immune system comes in and gets rid of the inflammation and actually ends up, you know, the reason exercise is good for us is because we end up with less inflammation overall, because the immune system has gone around and really like dampened inflammation everywhere.

36:43So probably sunlight sort of acts like exercise for the skin. And as with exercise, a little is probably better than overdoing it. But you're going to, yeah, you get, you keep your immune system trained and competent and less likely to overreact. So as our understanding is changing, and as you know, science is catching up on some of these things, and recommendations are shifting, maybe slowly, but they are shifting, I think people are always looking for for new ways to approach and how to think about things. I think you had a really

37:14nice, succinct way for people to think about how they should deal with sun exposure, both at the front and the back of the book. Do you want to lay that out for people? You're kind of, I think it was your seven word advice that you had for people? Totally. I shamelessly ripped it off from Michael Pollan, because I wanted to nod toward his book, In Defense of Food, because I sort of feel like we've been through this story with nutrition, and now it's happening again with sunlight. But yeah, so what we know is that it's very clear that spending too much time indoors is deleterious for your health. So boiling down to seven words,

37:49like he did, my seven are, get sun, not too much, go outside. So it's really that simple. If you're increasing your amount of time outside, it's almost certainly going to work out well for you overall. It's been a pleasure to talk with you, Rowan, and I've appreciated it. So thank you so much for taking the time to join us today. Thanks, Brian. This was a great conversation. Rowan Jacobson is a science writer and the author of In Defense of Sunlight, The Surprising Science of Sun Exposure.

38:28Next, a dermatologist provides practical advice about how to enjoy a sunny day. So if we're thinking about things like how do we stimulate some natural vitamin D? Now, between five to 30 minutes a day is sufficient. Of course, you don't want to expose yourself when the UV index is super high. This episode of our regular look at critical thinking on big picture science is skeptic check sunny days. When you need to build up your team to handle the growing chaos at work, use Indeed Sponsored Jobs.

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Dermatologist advice on safe exposure

39:40It's understandable to be in a daze after hearing the conflicting messages about sun exposure. We learn that many claims circulating online about the dangers of sunscreen are not supported by scientific evidence. But also, according to the latest science, some sunlight is beneficial to good health. Journalist Rowan Jacobson told us that when it comes to sunlight, we should follow the pithy rule of thumb. Get sun, not too much, go outside. But what exactly does that look like? Well, here with practical advice is a doctor who is used to helping people navigate skincare and their health.

40:15My name is Dr. Michelle Henry. I'm a board-certified dermatologist based in Manhattan, New York. I'm the founder of Skin and Aesthetic Surgery of Manhattan and a clinical instructor of dermatology at Weill Cornell Medical College. Dr. Henry provides a clinical perspective on how people can best protect themselves from sun overexposure while still soaking in all the good that sunshine provides. What is right for you, as it turns out, depends on a few different factors. So if we're thinking about things like how do we stimulate some natural vitamin D? Now, for those

40:49who've had skin cancer, my answer is always the safest vitamin D is to have vitamin D supplementation. But for those who are lower risk, who are pretty stringent with using their sunscreen use throughout the year, I say that between 5 to 30 minutes a day is sufficient. Of course, you don't want to expose yourself when the UV index is super high, but when it's a little bit lower. Five for those with fairer skin and potentially higher risk. You know, 30 minutes possibly for those with darker skin.

41:21So just to follow up on that, when you say somewhere between 5 minutes and 30 minutes sun exposure, do you mean without sunscreen on? Like you go out, maybe you go put the garbage out or something under a bright sun for about 5 minutes? Or should you always have the sunscreen on? Whenever you're outside for a prolonged period of time, we want you to always have your sunscreen on. But if you have fairer skin, you know, about 5 minutes a day without sunscreen is okay and sufficient to stimulate some lower levels of vitamin D. Now, if you are a higher risk person, you've had skin cancer, you have a high family history of skin cancer, again,

41:55all of these decisions are, you know, assessing risk. If you are higher risk, every time you're outdoors, I want you wearing at least SPF 30, SPF 50 if you're outside for more than an hour. If you're not someone who's very high risk, then I say, if you're on the fairer end of the Fitzpatrick scale, which is kind of the color scale that we use, you can stay outside for about 5 minutes without protection. If you're someone with darker skin, roughly about 30 minutes. What's interesting about the 5 minutes to 30 minutes is that's not a long time, but that's sufficient to generate some vitamin D and maybe like sun overexposure, vitamin D protection

42:31is accumulative. So if you do that every day, then maybe you get sufficient vitamin D. You're absolutely right. And so vitamin D stimulation is kind of, we call it logarithmic. So you stimulate more, you know, with your earlier exposures and then you kind of plateau. So you're not going to produce excess. So there's no need to sit out longer thinking you're getting hyper concentrated vitamin D. That's not how it works. And we really do just need very little exposure daily to make sufficient vitamin D for our overall health.

43:01And you said that if you were exposing your skin to the sun over time, you are at risk for skin cancer. If you are not protecting your, your skin. Exactly. UV light is, is radiation and it's a class one proven human carcinogen and it creates long lasting damage to our cellular DNA. And that DNA, when it then replicates, it passes along that damage and ultimately it can become a skin cancer. And so really our skin never forgets. So it is about balancing how much cumulative sun exposure you get.

43:37We've heard that skin cancer rates have gone up. Can you confirm that? And what is the rate of increase and over what period? So yes, if we look at melanoma specifically, I'm also, I'm on the board of the Melanoma Research Foundation. We had an increase this year of about 1%. So we expect about 235,000 roughly new melanoma cases in 2026. And that's about a 1% increase. And so, you know, it's, it's hard to figure out exactly why we're having this. Are we having more sun exposure? Is the UV light that

44:11we're getting now more potent? Or is it, which I'm inclined to believe that, you know, our public education has increased and more people are finding it. Physicians are finding it. Patients are coming in. So I think it may be that our surveillance has gotten better, more so than our risk has gotten worse. Well, skin cancer is the fear in all of this. And proponents of the anti-sunscreen movement, some of them believe that the sunscreen itself is leading to skin cancer. That's one extreme

44:43fear. Other fears have to do with the toxicity of sunscreen. How do you address those fears? It's kind of a range of fears having to do with sunscreen? Yeah, you know, those fears are not really based on the data. So the data we have, we do not have any data linking sunscreen or any of the filters to cancer. So that's just inaccurate. And when we talk about toxicity, you know, that word toxicity is so often used. But what if we double click on that, what changes do they believe are happening to create cancers? We don't have any evidence of

45:18cellular changes that are creating cancers. We just don't have that data. After years and years and years of using these sunscreens, we know that with the chemical filters, we do absorb a little bit and we do get a blood level. But in all the years of studying this, we've not seen any signs that we are causing any cancers, any lymphomas, any solid tumors of any sort with these filters. And for those individuals that are concerned about toxicity, a conversation that's not had enough is that we can use mineral sunscreens. So mineral sunscreens like zinc and titanium dioxide, we know zinc is in

45:53our food, titanium dioxide as well. And so, you know, these are mineral sunscreens that we do not absorb, right? And so there's not toxicity there. And so the fact that that conversation is never had kind of leads me to the fact that this conversation has become so popular because it's provocative, you know, it's a provocative conversation. A lot of what we see online is edutainment, not really education, right? But if someone is concerned about UV filters, even in the face of evidence that shows that they are not toxic in that way, they can use mineral sunscreens. And we have

46:26good data that mineral sunscreens are also very preventative. And so in many ways that should end the conversation, but unfortunately it has not. I wonder if you could reiterate for us the difference

Chemical versus mineral sunscreen differences

46:36between a chemical sunscreen, a mineral sunscreen, and is that the same as the difference between an organic sunscreen and a non-organic sunscreen? So we categorize sunscreens, we're categorizing them as mineral or physical, and we call those inorganic, right? And that's just a, that's based on their chemical structure, not based on where they're grown or what pesticides were used. That is just completely chemistry speak. So it doesn't, it doesn't correlate with how we commonly use inorganic and organic, but those mineral sunscreens are going to be actual minerals that reflect light.

47:12And so they're not absorbed by the skin. They're reflecting and scattering that UV light so it doesn't absorb. And so that's very different from a chemical. The chemical sunscreens are the ones that we actually call organic. And again, that's based on chemical structure. So those are things like abobenzone, oxybenzone, octanoctate. Those absorb UV light and they convert it to heat. And so those are kind of the two categories of sunscreens that we have. They function very differently. The chemical sunscreens are the ones that we do absorb a little bit. The mineral ones just

47:42sit on top of the skin and reflect and scatter and absorb UV light. One of the misconceptions about skin cancer, and you hinted at this, or actually you addressed it directly in the beginning of this interview, is that it only affects lighter skin people. And that is not true. Yeah, that's absolutely incorrect. So, you know, and when we talk about like individuals of quote color, there are people who identify as, let's say, black that could have the deepest, darkest mahogany skin ever. And then those who have, can have relatively fair skin, right?

48:15And so when we're looking at communities that are not a monolith, yes, if your skin is much much darker, your risk is a bit lower, but there are many, many variations. And I've even seen my own uncle who is a skin type 5, 6, like me, had a basal cell carcinoma on his eyelid. And those sorts of cancers, sun does play a role in that. So while it does play less of a role, it is still important to use sunscreen. And also for communities of color, there are so many reasons one should protect themselves from the sun. So skin cancer is one reason,

48:48but also, you know, obviously hyperpigmentation, accelerated aging, but also these are populations that may have higher rates of certain conditions like lupus and autoimmune conditions where they are, can be photosensitized. There are many, many reasons why sun protection is a good decision, skin cancer being one of them. But I think that's the reason we really should encourage safe sun exposure for everyone independent of their skin color. Well, Dr. Henry, is there any other misconception about using sunscreen or sun exposure that we

49:21haven't discussed here that you would like to bring up? Oh, absolutely. So I think one big one is that a lot of my patients still believe that a base tan is safe, that it's giving them some sort of protection, and it's not. So that's a big one. A lot of people say, well, our ancestors didn't use it. Well, our ancestors probably also died around 50 or 60, you know, like these are totally different lives. And maybe we did not find them, right? I'm sure there are many, many cancers that if we look back, I love looking at art. And there's a, gosh, I forget his name. He's a famous lecturer who really lectures a lot about

49:55diseases that we find in historical art. And there are cases of, you know, what we believe to be skin cancers that were found that we didn't know how to identify them at that time. And so I think that when you know better, you know, you make better decisions. And today we know. And so moving forward with the evidence, I think, is what's most important. Well, Dr. Michelle Henry, thank you so much for joining us and helping to clear up and synthesize some of the ideas that we heard earlier in the show. Thank you so much. Thanks for having me. Michelle Henry is a dermatologist and clinical

50:29instructor at Weill Cornell Medical College. The big picture perspective in this episode, Despite the compelling claims and pyrotechnics of online anti-sunscreen proponents, the claims about the harmful effects of sunscreen are not supported by scientific evidence. But also the latest science suggests that some sunlight is beneficial to our health. How much you should get depends, as Dr. Henry outlined.

New FDA approved sunscreen filter

50:54But as the sun sets on this episode of Big Picture Science, we leave you with a bit of bright news. After more than 30 years, the FDA has finally approved a new sunscreen filter that has been used for decades in Asia and Europe. BMORTRIZENOL, or BEMT for short, is a chemical filter that provides broad-spectrum coverage without being absorbed into the skin, like other chemical filters, and without leaving a white cast, like most mineral sunscreens do. With BEMT sunblock options expected to be available in the U.S. soon, it seems there's a bright future ahead

51:29for sun protection.

51:45This show would not be possible without the sunny dispositions of senior producers Seth Shostak and Gary Niederhoff, producers Shannon Rose Geary and Brian Edwards, and contributors Sikon Akbon and Roland Pease. I am the executive producer of Big Picture Science, Molly Bentley. Also a big thanks to our listeners and to our Patreon supporters. The original music in the show is by Dewey DeLay and June Miyake. In this episode of Big Picture Science, which looks at how misinformation about sun protection has spread and new research about how sunlight affects our bodies is Skeptic

52:18Check, Sunny Days.

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