Sunscreen: Could It Be Toxic??

Sunscreen is supposed to protect us from dangerous stuff like cancer, but all over social media, people are saying that we’ve been getting it all wrong. We’re being told that our sunscreen is full of toxic chemicals, that wearing it could mess with our vitamin D levels — even that sunscreen itself actually increases our risk of skin cancer. So, what can the science tell us here? Should we toss our SPF-filled creams and sprays in the bin?? And could the answer here be different depending on your skin tone? We talk to researchers Dr. Brandon Adler, Prof. Rachel Neale, and Dr. Adewole Adamson to find out. Find our transcript here: https://tinyurl.com/ScienceVsSunscreen In this episode, we cover: (00:00) The internet freak-out over sunscreen (05:06) Is sunscreen toxic? (20:46) Does sunscreen mess with vitamin D? (29:29) Does sunscreen work to prevent skin cancer? (34:40) Do people with darker skin need sunscreen? (44:38) How to wear sunscreen correctly This episode was produced by Michelle Dang, with help from Meryl Horn, Rose Rimler and Ekedi Fausther-Keeys. We’re edited by Blythe Terrell. Wendy Zukerman is our executive producer. Fact checking by Erica Akiko Howard. Video editing and sound by Bobby Lord. Music written by Bobby Lord, Bumi Hidaka, So Wylie, Emma Munger and Peter Leonard. Thanks to Humdinger Studios in Melbourne and Wolff Island Studios in New York City. Science Vs is a Spotify Studios Original. Listen for free on Spotify or wherever you get your podcasts. You can also find us on YouTube, TikTok and Instagram. Learn more about your ad choices. Visit podcastchoices.com/adchoices

• 0:00Speaker 00

  Wait, so the melanin sites, the cells that make the melanin, then the melanin is like sunscreen for your DNA? Like natural sunscreen for your DNA?

• 0:15Speaker 01

  Yeah, so like this melanin, it's directly responding to the sun. It's moving up there and it's wanting to protect you from those UV rays. And in essence protects you from the DNA damage that could cause skin cancer.

• 0:31Speaker 00

  Wow, that's so cool. Hi, I'm Wendy Zukerman and this is Science Versus. Today on the show, we're pitting facts against frying in the sun.

• 0:48Speaker 00

  We're talking about sunscreen. All over social media, people are telling you to ditch your sunscreen. They say that it's doing us more harm than good. Like, some say that if you really want to be healthy, you shouldn't be blocking out the sun's gorgeous rays at all. You should be going outside and letting the sun help us make that sweet, sweet vitamin D.

• 1:13Speaker 02

  No sunscreen, no fear. Just me and the light, my body was begging for. Vitamin D is free, it's powerful, and it's meant for us.

• 1:23Speaker 00

  Others claim that sunscreen itself is straight up toxic, that it seeps dangerous chemicals into our blood and might even be messing up our hormones. I'm going to show you what they're putting in our sunscreen, and it's going to make you just as mad as it's made me.

• 1:37Speaker 03

  Most people don't realise how toxic our sunscreens are. Two hours after applying it to the skin, these toxic environmental estrogens can actually be detected in the blood.

• 1:47Speaker 04

  And this is exactly why I stopped using toxic sunscreens from the grocery store.

• 1:52Speaker 00

  But of course, a lot of us wear sunscreen to protect our skin from skin cancer. The problem is that now I'm hearing of scientific studies that apparently show sunscreen could be causing cancer? Ah, what is going on here?

• 2:09Speaker 05

  When they compare sunscreen users to non-sunscreen users, the sunscreen users face increased risks of all the major skin cancers.

• 2:16Speaker 06

  We use more of this chemical sunscreen than we ever have before. Skin cancer rates increasing. You've got to just use your head for a minute.

• 2:23Speaker 00

  All of this has led people to say, stop buying sunscreen. Or online, you can even find people giving recipes on how to make your own sunscreen at home. This is your answer? Get that bull**** out of your life and start using a really good quality sunscreen. So what is going on with sunscreen? Should we use it or not? Is it making us vitamin D deficient and leaching toxins in our blood? And if we still want to use it, are some sunscreens safer than others? When it comes to sunscreen, there's a lot of...

• 2:55Speaker 03

  Most people don't realise how toxic our sunscreens are.

• 3:00Speaker 00

  But then, there's science.

• 3:06Speaker 00

  Science Versus Sunscreen is coming up just after the break. If you have a friend who's worried about sunscreen, maybe share them this episode.

• 3:20Speaker 07

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• 5:28Speaker 00

  Welcome back. Today on the show, we are looking into whether sunscreens are dangerous? Should we be slapping them on our bodies? To tell us all about it is producer at Science Versus, Michelle Dang.

• 5:41Speaker 01

  Hey, Wendy.

• 5:42Speaker 00

  Michelle, sunscreen, this question of whether sunscreen is safe has been in the zeitgeist for so long. I feel like you've wanted to do this episode for ages.

• 5:54Speaker 01

  Yeah, I think I pitched it like seven years ago when I was an intern.

• 5:58Speaker 00

  Wow, no, did you really?

• 6:00Speaker 01

  So it's taken us a while, but we're coming back to it.

• 6:02Speaker 00

  I know, and you know, as you've been sort of like, I'm getting whispers of the science that you've been finding, and it's making me wonder, you know, have I just been swallowed by big sunscreen? By the sunscreen propaganda machine? It's making me question everything I think I know about sunscreen.

• 6:20Speaker 01

  I do always hear online Australians talking about Sid the Seagull? The Seagull?

• 6:25Speaker 00

  What, you got a problem with Sid now? The Seagull?

• 6:29Speaker 01

  No, tell me more.

• 6:30Speaker 00

  So, but the uninitiated Sid the Seagull was this seagull that for decades has taught Australians how you've got to put sunscreen on and more broadly protect yourself from the sun. And Sid would tell us, and he says, you've got to slip, slop, slap.

• 6:56Speaker 00

  So you slip on a t-shirt, you slap on a hat, and you slop on some sunscreen?

• 7:02Speaker 01

  I thought it was all like slip, slop, slop, sunscreen, but...

• 7:05Speaker 00

  Yeah, it's a whole, a whole array of things you've got to do. Have I been lied to all my life? I mean, presumably sunscreen is protecting my skin, but now we're sort of hearing that it's also getting into my body, these chemicals from the sunscreen getting into my body, causing damage. So what's going on? Where do we begin?

• 7:27Speaker 01

  Yeah, let's start there about all these claims about sunscreen being toxic for us. And so people will often point to all these active ingredients that we find in sunscreens. And there is this one ingredient in particular that I want to focus on called oxybenzone. This one, people are particularly worked up about.

• 7:48Speaker 00

  Oxybenzone, okay. What is it actually doing in the sunscreen? Why is it there to begin with?

• 7:53Speaker 01

  So it's one of the ingredients that's there to literally help filter out the sun.

• 7:58Speaker 00

  Right, the UV rays.

• 7:59Speaker 01

  Mm-hmm.

• 8:00Speaker 00

  Right, and why are people worried about it?

• 8:02Speaker 01

  Yeah, so some of these worries about oxybenzone go back years, even decades. So for example, I want to tell you about this one study that came out in 2001 that looked at rats and oxybenzone.

• 8:14Speaker 00

  Okay.

• 8:15Speaker 01

  So in this study, scientists took a bunch of young female rats and exposed them to the chemical. And what they found was that it made their uteruses grow bigger, and not in a good way.

• 8:29Speaker 01

  So this, this suggested that chemicals like oxybenzone were acting like estrogen or essentially hormone disruptors.

• 8:39Speaker 00

  Oh.

• 8:40Speaker 01

  This really freaked people out. It's been a very widely cited study.

• 8:44Speaker 00

  Yeah, yeah, I'll bet. But of course, it's just, you know, rat. I mean.

• 8:49Speaker 01

  Yeah, and it's not just that it's just in a rat. There's a couple of other things that were going on that don't mimic how we, we as humans use sunscreen. For example, um, they made the rats eat the sunscreen chemicals. They basically spiked their rat chow with it.

• 9:05Speaker 00

  Uh huh. I was gonna ask, did they put it on their fur? But so they were, they were eating the chemicals. That's not how we do it. And then how, how much of the stuff were they getting in their bodies? Is it at all related to what I might get if I absorb it through my skin?

• 9:22Speaker 01

  That's the next point. They, they gave them a lot of it. So I talked about this with Dr. Brandon Adler from Keck Medicine of the University of Southern California. And he told me that it would take a long time to get this level of exposure that the rats did.

• 9:38Speaker 05

  Looking at humans, it was estimated that would take anywhere between about thirty five and two hundred and seventy seven years of use of oxybenzone-containing sunscreen.

• 9:51Speaker 01

  Oh, my gosh.

• 9:51Speaker 05

  Anywhere between thirty five and two hundred and seventy seven years. And the shortest scenario would require applying sunscreen to absolutely every part of our bodies.

• 10:03Speaker 00

  Right, so this is a classic case of the dose makes the poison. And Brandon's basically saying these were unrealistic levels of these chemicals. Even for me, avid sunscreen user, I wouldn't be getting this much sunscreen into my system in such a short space of time, right?

• 10:22Speaker 01

  Exactly, yeah, yeah.

• 10:24Speaker 00

  Okay, and it's a study in rats. So do we have anything in people that there's more realistic? That can help us understand if these chemicals are dangerous?

• 10:33Speaker 01

  Right, yeah, so to get to the bottom of this, I want to tell you about these couple of FDA studies that came out right before the pandemic. And they did what are called maximum usage trials, where they bring people into the lab. And over multiple days, they slather sunscreen like all over their bodies.

• 10:51Speaker 00

  Sounds fun, it's like my dream.

• 10:52Speaker 01

  Here's Brandon.

• 10:54Speaker 05

  So sunscreen was applied to seventy five percent of the body's surface area. If you, if you look at a chart of what that means, that, that is a lot of your body. Um, that's essentially everywhere besides maybe your bikini zone.

• 11:08Speaker 00

  How many weeks were they getting that sunscreen on for?

• 11:11Speaker 01

  Four or five days total in the lab.

• 11:13Speaker 00

  And then what did the researchers do next?

• 11:15Speaker 01

  Um, so then they, they measured their blood throughout that study, but also twenty one days afterward. And they looked to see like how much of this chemical was showing up in the blood. And we did see oxybenzone there. And it was in a high enough level that it passed this FDA threshold. And this is something that people online really love to point out.

• 11:39Speaker 05

  Now, it's very easy for this to lead to headlines, right? Sunscreens are absorbed into the body. And then you very, very quickly get words like toxic and dangerous to get thrown out.

• 11:53Speaker 00

  I mean, yeah, it doesn't, it doesn't sound great. That's the, yeah, that our body is absorbing these. And twenty one days later, they're found in our blood at all. I don't love.

• 12:08Speaker 01

  I know.

• 12:09Speaker 00

  And then at some increased threshold level, obviously, our scientist friend doesn't sound concerned.

• 12:19Speaker 01

  Oh, so like those FDA studies, that threshold was very like misleading. People kind of took that and ran with it and said like, hey, look, sunscreen is toxic.

• 12:28Speaker 00

  Yeah, yeah.

• 12:29Speaker 01

  But the, the threshold in those studies didn't actually suggest danger at all. In fact, the FDA concluded that study, quote, "These findings do not indicate that individuals should refrain from the use of sunscreen," end quote.

• 12:43Speaker 00

  So if they were at very high levels, toxic, dangerous levels, what would you start to see?

• 12:51Speaker 01

  Yeah, so I found the systematic review of around thirty studies. And they looked at like, um, studies are kind of trying to find out like, does oxybenzone actually affect our hormone levels?

• 13:03Speaker 00

  Okay.

• 13:03Speaker 01

  And what they concluded was that there's no clear evidence in the literature that oxybenzone actually harms us.

• 13:11Speaker 00

  Uh huh, so it, it looks like at the doses that most people are getting their sunscreen at, um, we don't need to worry here.

• 13:19Speaker 01

  Exactly, yeah.

• 13:20Speaker 00

  And what about the coral reef? People are very worried about the coral reef. Your sunscreen is killing the coral reefs. Oxybenzone, which has been known to bleach our coral reefs. It can damage coral reefs and wildlife, so you don't want to do that. So do I need to worry about that?

• 13:37Speaker 01

  Yeah, so oxybenzone is one of those chemicals that has been banned in places like Hawaii.

• 13:42Speaker 00

  Uh huh, because they're worried about their coral reefs?

• 13:45Speaker 01

  Yeah, they're worried about their coral and the bleaching.

• 13:47Speaker 00

  Uh huh.

• 13:48Speaker 01

  When you take a closer look at these studies, the science is also a bit more nuanced. Like scientists would bring young coral into the lab and then expose them to these sunscreen chemicals and find that it was toxic to their DNA, it caused coral bleaching. But when you look in a real world setting and actually measure the amount of this stuff that's floating around in the ocean, we don't see it in as, nearly as high scary levels.

• 14:16Speaker 00

  Mm hmm, it's all about the dose, uh huh.

• 14:20Speaker 01

  Yes.

• 14:20Speaker 00

  It's all about the dose, whether you're talking about the coral, whether you're talking about the people.

• 14:23Speaker 01

  Mm hmm.

• 14:24Speaker 05

  We know beyond a shadow of a doubt that the primary cause of coral bleaching is climate change, right? That's been shown now. It has been suggested by more realistic and moderate studies that sunscreen exposure, especially oxybenzone, may add what they call insult to injury. But it's certainly not the primary cause of the decimation of coral reefs that we've been seeing.

• 14:49Speaker 00

  Guys, it's climate change.

• 14:51Speaker 01

  But despite that, uh, all of these studies did lead to some changes. A bunch of manufacturers have taken out this chemical oxybenzone from their sunscreens anyway, because people just weren't buying them from the shelf anymore.

• 15:05Speaker 00

  Oh, okay, because consumers didn't want it. And so what are they putting in the sunscreen these days? Should we be worried about that?

• 15:11Speaker 01

  Well, here's the thing, like, people are worried about all the other ingredients that come in, in sunscreens. There's a bunch of other chemicals that also showed up in these same studies. Uh, but the story is, is pretty much the same. Like, they do get into our blood, but we have no evidence that they hurt us. And, um, as someone who has dug into the research, Brandon isn't worried about them.

• 15:37Speaker 05

  I have chemical sunscreens on my face right now. I was outside this morning in the, you know, early morning sun, and I applied chemical sunscreens. So I personally do not believe that there is a significant risk with routine use of these ingredients.

• 15:53Speaker 00

  Hmm, and he said chemical sunscreen. Aren't all sunscreens chemical sunscreens?

• 16:00Speaker 01

  So they can break down into like two major pools. There's chemical sunscreens and then there's mineral sunscreens.

• 16:08Speaker 00

  Oh, yes, I have heard this. Sounds like marketing fluff.

• 16:15Speaker 01

  No.

• 16:16Speaker 00

  This isn't at all chemicals.

• 16:17Speaker 01

  No, mineral sunscreens are legit.

• 16:19Speaker 00

  Are they really? What is the difference? It sounds, it's like it's all a chemical. But mineral sounds, you know, like a nicer chemical you'd get at a spa.

• 16:27Speaker 01

  Yeah, I mean, it's a little, to get a bit nerdier, um, the chemical sunscreens have organic molecules in them. And the mineral sunscreens have inorganic ones. These are things like zinc oxide.

• 16:40Speaker 00

  So by organic chemical, just because I don't want the audience thinking that means it doesn't have pesticides in it, you mean it's carbon-based?

• 16:47Speaker 01

  Yeah, mm hmm.

• 16:49Speaker 00

  Okay, and then inorganic, like zinc oxide, no carbon in it. And are they, are they better?

• 16:56Speaker 01

  So the people who are maybe still freaked out about the fact that chemical sunscreens get into your blood at all, um, mineral sunscreens are the other option, because they more so like sit on the surface of your skin and they don't go down into your blood in the same way as those chemical sunscreen ingredients.

• 17:14Speaker 00

  Uh huh.

• 17:15Speaker 01

  However, they are more likely to give you a white cast.

• 17:18Speaker 00

  They leave a white cast on your skin, uh huh. And then these DIY sunscreens that people are making, I mean, do they work?

• 17:31Speaker 01

  Yeah, I was curious about that, too. So I asked Brandon.

• 17:34Speaker 05

  And what I'm seeing more and more is that whenever an ingredient or a product gets called toxic, the next sentence is, let me sell you a non-toxic alternative. And this is when we get into homemade recipes for sunscreens that we're finding on the internet. People are turning to making their own sunscreens with zinc oxide and beef tallow.

• 17:59Speaker 00

  How are they getting the zinc oxide from sunscreen? Is this like The Simpsons? You made a spoon out of a bigger spoon?

• 18:05Speaker 01

  I gotta process that for a second. You made a spoon out of a bigger spoon?

• 18:10Speaker 01

  I guess they're buying the mineral. But it's true.

• 18:13Speaker 00

  Right, like you took sunscreen and then made a different sunscreen out of it? Like you just added beef tallow to the sunscreen you bought at the store?

• 18:20Speaker 01

  I actually found one study that looked into these kind of online recipes. What they did was find 15 recipes from online and they whipped them up in the lab and then tested them out.

• 18:33Speaker 00

  Ooh, and what did they find?

• 18:34Speaker 01

  It turns out a few of them didn't even have anything in them that could act as a sunscreen. And then the rest were less than an SPF of six.

• 18:44Speaker 00

  Uh huh, which is unlikely to help you.

• 18:47Speaker 01

  It's not gonna help you, yeah.

• 18:49Speaker 05

  When people have looked at how effective these homemade sunscreens are, they really aren't at all.

• 18:56Speaker 00

  So don't DIY your sunscreen. No shockers there.

• 19:00Speaker 01

  For those of us in the US, there is some sunscreen news. There was this chemical sunscreen ingredient that was recently approved. It's called bemotrizonal. And it's the first sunscreen ingredient that we've gotten approved in like 20 years.

• 19:15Speaker 00

  Wow, good job. Good, good work, guys. Been in Australia for a while, this ingredient, and Europe. But why, why are people getting excited about it?

• 19:25Speaker 01

  Yeah, so I talked to Brandon about it and he says it has a lot going for it.

• 19:29Speaker 05

  I would say the US is just barely catching up. So bemotrizonal does a great job being a true broad spectrum sunscreen ingredient. It is very stable and mixable with other sunscreen ingredients, which is a real plus here. And in addition, bemotrizonal is a large molecule that is not easily absorbed into the skin or into the body.

• 19:54Speaker 00

  Mm hmm. So, okay, so it doesn't get absorbed too much? So it's kind of like the mineral sunscreens? What are some other benefits?

• 20:02Speaker 01

  So it's, it's very stable. So the sun, like, you know how you have to reapply sunscreen every couple of hours? But this means that it's a little bit more stable. It's probably gonna protect you for a little longer. So kind of guarantee your safety a bit more. And then it also, if you've heard about like European and Asian sunscreens being like really nice and easy to sort of like rub into your skin, just like applies really nicely and finely. This kind of, why are you laughing?

• 20:34Speaker 00

  It just feels like this classic, like the garage is greener. Over there, they have the best sunscreens in the world.

• 20:40Speaker 01

  It's true, though. Have you tried Korean sunscreen?

• 20:44Speaker 00

  I guess I've traveled. I just shove it on my face. I didn't think too deeply.

• 20:48Speaker 01

  Yeah, I mean, maybe you've had the good one all along, though.

• 20:51Speaker 00

  It's true, it's true.

• 20:52Speaker 01

  It's been 20 years and we've been without it.

• 20:55Speaker 00

  Okay, it's true. So it rubs it, it rubs it nicer?

• 20:58Speaker 01

  Yeah.

• 20:59Speaker 00

  And then when you have studies look to see if it gets into your blood?

• 21:04Speaker 01

  Yeah, there's been studies and it does not get into the blood in the same way. It sits on top more like the mineral sunscreens.

• 21:12Speaker 00

  Oh, awesome. So will you be buying that one now?

• 21:14Speaker 01

  Yeah, for sure. I'm gonna keep an eye out for it.

• 21:17Speaker 00

  Mm hmm. Okay, so here's where we're at so far. Your sunscreen is not toxic, although it does have chemicals in it that, depending on the kind of sunscreen you get, may turn up in your blood. And in super high doses, that can cause trouble, particularly in rats or in rat studies. But most of us, all of us, are probably not getting those high scary doses.

• 21:49Speaker 00

  So, so far, I'm sticking with my sunscreen regime, Michelle.

• 21:55Speaker 01

  Okay, sounds good.

• 21:56Speaker 00

  But what's coming up after the break?

• 21:58Speaker 01

  After the break, we're gonna be looking at vitamin D.

• 22:01Speaker 00

  Ooh, yes, because that could change things for me. And I have always wondered, am I blocking out too much of the sun's rays? Am I lowering my vitamin D levels too much?

• 22:17Speaker 01

  Yeah, with your sunscreen, right? Yeah.

• 22:19Speaker 00

  Yeah. And while we're heading into the break, if you have a friend who's afraid of sunscreen, maybe send them this episode.

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• 24:35Speaker 00

  Welcome back. Today on the show, we're talking all about sunscreen. Should you stop wearing it? Next up, vitamin D. We know it's important. Is sunscreen the reason that your vitamin D levels are too low? Michelle Dang, producer at Science Versus, tell us the science.

• 24:53Speaker 01

  Yeah, so let's start with why vitamin D is so important. It's like this middle manager that helps calcium get absorbed into our gut. And we need calcium to keep our bones strong, right? So a really bad vitamin D deficiency actually can make your bones start to become soft and even break more often. And this can manifest as a disease called rickets in kids or osteomalacia in adults. So I talked about this with Professor Rachel Neal from QIMR Bergheffer Medical Research Institute in Australia. And she was like, yeah, you really don't wanna go through this.

• 25:32Speaker 06

  So certainly being really badly vitamin D deficient, that's worrying and that needs to be corrected rapidly.

• 25:40Speaker 00

  Yeah, I mean, vitamin D deficiency has also been linked to a bunch of chronic diseases, right?

• 25:45Speaker 01

  Yeah, we think it might play a role in the immune system. And there's a bunch of studies linking it with things like having worse COVID, worse cancer outcomes, multiple sclerosis.

• 25:56Speaker 00

  Yeah, so super important. So is wearing sunscreen a risk factor here?

• 26:00Speaker 01

  Yeah, so, you know, we get some vitamin D from our food, but most of it we get from the sun.

• 26:07Speaker 00

  And so how, how exactly does that happen? Does the sun stimulate vitamin D in us?

• 26:14Speaker 01

  Yeah, so it's, it's super cool. And it's one of the only vitamins that our body can actually make. And it happens from the sun, which is just crazy. So what happens is that the, the rays from the sun hit our skin cells. And inside our skin cells, there are, there's this chemical that's a cholesterol. And when the UV rays hit that chemical, it changes shape a couple of times from the energy. And then that molecule goes on to become vitamin D. It leaves the skin, goes into our blood. And then here's Rachel to tell you about the rest.

• 26:52Speaker 06

  It gets carried in our bloodstream to the liver and then that molecule gets carried to the kidneys and to other cells to become the active form of vitamin D so it can do what it needs to do.

• 27:03Speaker 00

  Okay, so how much sunlight do we need to get enough vitamin D in our lives?

• 27:11Speaker 01

  Yeah, so it can, it can depend on several different things, like where you live, the time of the day, the time of the season. But just for example, it can be really fast. Rachel told me if you went out in the middle of a summer day in Brisbane, on the east coast of Australia.

• 27:29Speaker 06

  It takes about five minutes wearing shorts and a t-shirt.

• 27:33Speaker 01

  Wow, that's really quick.

• 27:34Speaker 06

  It's not long, yeah?

• 27:36Speaker 01

  Now, that's if you have pale skin, like Rachel. And another important part here is if you have darker skin, it's going to take longer, about like 20 minutes under the same conditions.

• 27:47Speaker 00

  Uh huh, to get enough vitamin D for your daily needs.

• 27:50Speaker 01

  Mm hmm. And, you know, that's in Australia. There are probably across different places in the world, if you're looking at summer and you're looking at midday, you see a similar thing.

• 27:59Speaker 00

  Okay.

• 28:00Speaker 01

  Winter, it's gonna take longer. 6:00 AM, it's gonna take longer.

• 28:04Speaker 00

  But it's not huge amounts of time, so.

• 28:09Speaker 00

  Does sunscreen affect this? Or do you kind of just get enough sun, even if you put sunscreen on, to get your vitamin D needs?

• 28:19Speaker 01

  It's a valid question because the same exact UV ray that we need to create vitamin D, it's called UVB rays, is the same exact one that sunscreen is designed to block. So let me tell you about a study that we have, which was done by Rachel and her team, where they wanted to test this all out. Does sunscreen affect your vitamin D levels? And so they did this study in Australia and they gathered 600 people for it who said that they don't wear sunscreen that often, about two or less times a week. And then they split them into two different groups. One of them, they told, like, just carry on as usual, do what you're doing.

• 29:05Speaker 01

  The other group was told to put on sunscreen in the morning. Every time, it was forecasted that the sun was going to be strong enough to harm their skin. And for the sunscreen nerds out there, that's when the UV index is at-

• 29:20Speaker 00

  UV three.

• 29:21Speaker 01

  Or higher. Yes, you got it.

• 29:24Speaker 00

  Okay.

• 29:25Speaker 01

  And that's pretty much every day in Australia, except for the winter. So on these days, the sunscreen group were told to wear SPF 50 sunscreen and they had to wear it everywhere that they had skin exposed. And to make sure that they actually used it when they were supposed to, Rachel and her team bugged them a lot about it.

• 29:46Speaker 06

  We sent them text message reminders every week saying the UV index is going to get to three this week. Make sure you use your sunscreen. And we phoned them and we, you know, made sure that they were doing it as much as they possibly could.

• 29:58Speaker 00

  And how long did this go on for?

• 30:00Speaker 01

  A whole year.

• 30:01Speaker 00

  A year?

• 30:02Speaker 01

  Yeah.

• 30:03Speaker 00

  Wow, what an amazing study. Okay, so what did they find?

• 30:07Speaker 01

  So they measured the vitamin D levels at the beginning of the study, after the summer and after the winter. And what they found was that throughout the summer, it looked like, on average, vitamin D levels were fine. Levels were going up in both groups. And they didn't see vitamin D deficiencies across the board in the sunscreen group.

• 30:30Speaker 00

  Oh, so in summer, the groups had the same amount of vitamin D? It wasn't just that the sunscreen group wasn't deficient? They actually were all making an equal number, on average, of vitamin D?

• 30:45Speaker 01

  Well, actually, to clarify, the people wearing sunscreen nearly every day actually made a little bit less vitamin D than the control group.

• 30:55Speaker 00

  Got it.

• 30:56Speaker 01

  And so, you know, like, people wearing sunscreen were still making, they were still making vitamin D because we know that sunscreen's not like a perfect blocker. It still lets in some of those UV rays.

• 31:07Speaker 00

  What happened in winter then?

• 31:10Speaker 01

  Yeah, so they kept following these people and by the end of winter, they did notice something very interesting.

• 31:17Speaker 06

  And there was about a 35% increased risk of being vitamin D deficient at the end of winter in the sunscreen group than in the control group.

• 31:26Speaker 00

  Ooh, I mean, they were really wearing a lot of sunscreen there. But what does Rachel make of this?

• 31:36Speaker 06

  I was really surprised by the results.

• 31:42Speaker 00

  Okay.

• 31:43Speaker 01

  Now, everyone in the study made less vitamin D in the winter, which is what you'd expect.

• 31:48Speaker 00

  Yeah.

• 31:50Speaker 01

  But the fact that the sunscreen group made less vitamin D throughout the summer is what made the difference here. Because another interesting thing is that our bodies can actually hold on to vitamin D in our fat tissues and release it slowly over several months. I asked Rachel, was it that the daily sunscreen wearers built up less of a storage, like a store of vitamin D that would last them through the winter?

• 32:18Speaker 06

  Through the winter, correct, yeah. So the store ended up lower at the end of summer, which meant that as they went down in winter, they ended up lower at the end of winter. And if you imagine that that happened year after year after year, so you've used sunscreen for a year, you're lower in winter, you go up less in summer because you're using sunscreen every day. So now your store's even lower than it was. You end up even lower at the end of the following winter. So with these repeated yearly cycles, you can imagine that if you did this all the time, you could end up quite deficient.

• 32:50Speaker 00

  So I guess now we play the game of risks and benefits, Michelle. So, okay, wearing a lot of sunscreen does put you at a risk of vitamin D deficiency.

• 33:07Speaker 00

  But we're not doing this for fun. We're doing this to protect our skin from cancer,

• 33:16Speaker 00

  effects of aging. So is that still real? Because some people online say even that's a lie.

• 33:23Speaker 01

  So yeah, here's the concern with skin cancer. Those UV rays from the sun are coming down, hitting our skin, getting through those cells to the DNA and causing a mutation in that DNA.

• 33:35Speaker 00

  Yes.

• 33:36Speaker 01

  And then again, we're talking about doses. Repeated exposure to the sun can help those mutations accumulate over time.

• 33:44Speaker 00

  Yes, yes. This is what we've known for a long time. So why is... And then the obvious next step would be if you can wear sunscreen, block those UV rays, reduce the chance of DNA damage, you can protect your skin. That's the line from the health authorities, Michelle. But is it true when we look at the new science?

• 34:09Speaker 01

  So when we get into the real world studies, it gets a little bit messy. The kind where they gather a bunch of people, ask them about their lifestyle and what they do, whether they wear sunscreen, and then later look to see, you know, do they have skin cancer?

• 34:25Speaker 00

  Yeah.

• 34:26Speaker 01

  And some of these studies find that some people who wear more sunscreen get less skin cancer.

• 34:32Speaker 00

  Yeah, what you'd expect.

• 34:34Speaker 01

  But, you know, not every study finds that. People really like to point to this one study that was done in 2023 out of the UK.

• 34:43Speaker 00

  Okay.

• 34:43Speaker 01

  Where it looked at the health data of over 400,000 people. And it found that people who wear more sunscreen more often are more likely to get skin cancer.

• 34:55Speaker 00

  Wait, so that people who wore more sunscreen were more likely to get skin cancer?

• 35:03Speaker 01

  Mm-hmm, yes.

• 35:05Speaker 00

  That sounds, this big study, 400,000 people, it sounds damning for the sunscreen propagandists out there like me. But it is making me wonder, could it be that the people who were wearing more sunscreen were actually out in the sun more often? And they were badly applying sunscreen? And that's why they had more skin cancer?

• 35:33Speaker 01

  Yeah, you are right on track. The authors of this study, like, came out to say that people online are misinterpreting this study. And even though they found a link, what's likely really happening here is that people who wear more sunscreen are more likely to go outside and be outside in the sun, but maybe under this, like, false security. Because maybe they're not wearing it enough, they're not wearing enough of it or, you know, not reapplying and that kind of thing.

• 36:01Speaker 00

  So do we have any better studies here that can help us?

• 36:04Speaker 01

  Yeah, so Wendy, we actually have one RCT, randomized controlled trial. And this one happened in Australia. It looked at 1,600 people. And similar to Rachel's study, it split these people into two different groups. One was given sunscreen and told to wear it every day. And the other was told to carry on as usual, do whatever they want.

• 36:26Speaker 00

  Okay.

• 36:27Speaker 01

  And Wendy, they followed these people for over a decade.

• 36:30Speaker 00

  Wow. This is an amazing study. This is exactly what we need. 1,600 people followed for a decade? Because skin cancers can take a while to develop. So what did they find? Did the sunscreen group get less cancer?

• 36:46Speaker 01

  Yeah, so they looked to see who in the study got skin cancer. And there are three main types of skin cancer. There's squamous cell carcinoma, basal cell carcinoma, and then there's the scary one, melanoma, which is more likely to spread and kill you. And what the RCT found was that the sunscreen worked pretty well for that one type of skin cancer, squamous cell carcinoma.

• 37:12Speaker 00

  Mm hmm.

• 37:13Speaker 01

  It basically dropped cases forty percent between the two groups.

• 37:17Speaker 00

  Aha, aha, but what about melanoma?

• 37:20Speaker 01

  Yeah, so when it came to melanoma, the evidence was actually less clear.

• 37:25Speaker 00

  Interesting.

• 37:26Speaker 01

  There was eleven people who got melanoma in the sunscreen group versus twenty-two in the control group.

• 37:33Speaker 00

  That's a fifty percent lower risk, Michelle.

• 37:36Speaker 01

  Yeah, but it actually didn't come out too statistically significant, probably because the cases were just too low.

• 37:42Speaker 00

  Hmm, okay. Interesting. It does seem like then sunscreen's still protecting you from skin cancer. That story is still true. Even if it's not your silver bullet, right?

• 37:54Speaker 01

  And yeah, like the dermatologists I spoke to, they're like, hey, if we were to redo this study, um, looking at melanoma, which is the scarier one.

• 38:02Speaker 00

  Hmm.

• 38:03Speaker 01

  Maybe the, the data would be even stronger today because back then they were using SPF sixteen and now we're using SPF thirty, SPF fifty.

• 38:12Speaker 00

  And in that study, did it matter about your skin tone? If you have darker skin or lighter skin, does that affect your risk here?

• 38:19Speaker 01

  Yeah, so here's the thing with that study, most of the people in it were white.

• 38:24Speaker 00

  Mm hmm.

• 38:25Speaker 01

  Uh, which brings us to this other idea where some people say that people with darker skin don't get the same benefits from sunscreen.

• 38:33Speaker 00

  Okay, well, we already know if you've got darker skin, you're at an increased risk of vitamin D.

• 38:37Speaker 01

  Right.

• 38:38Speaker 00

  Deficiency, so if we're playing this risk benefit game, gotta be some strong benefits here. Is it true that if you have darker skin, you're at a lower risk of skin cancer?

• 38:48Speaker 01

  So I talked about this with Dr. Ade Adanson, who's a dermatologist from Dell Medical School at University of Texas, Austin. And, um, based on Ade's own experiences in the clinic, like with melanoma, he told me.

• 39:01Speaker 13

  Well, one, as a dermatologist, if I just think about the people that I see, right? Um, and like, I can maybe, I can only maybe think of one or two black people that in, you know, doing this for fifteen years, having actually seen or diagnosed one, right? You don't see it.

• 39:21Speaker 00

  A melanoma? He's talking about melanoma specifically?

• 39:23Speaker 01

  Yes, exactly. If you look at the data, um, people of color do get melanoma a lot less than white people. For example, a black person's risk of getting melanoma is thirty to forty times less than a white person. And that's specifically the kind that spreads. And, and not only that, when it does show up in, in people with darker skin, it's often showing up in a very particular way.

• 39:48Speaker 13

  You know, people of color, they mostly get, um, uh, melanoma on the palms of their hands, soles of the feet, places that are not related to sun exposure.

• 39:59Speaker 01

  So, so all of this was very like curious to Ade and he wanted to take a step back and understand whether sun exposure is linked to melanoma in people of color in the first place. Like, is there a connection here at all? And so he said.

• 40:14Speaker 13

  You know what? Let me do a systematic review, which is the top of the evidence pyramid, right? You, you know, you get all the studies looking at this.

• 40:22Speaker 01

  Mm hmm.

• 40:23Speaker 13

  And see what, what comes out of it. Is there actually data to support UV is an important risk factor for melanoma?

• 40:30Speaker 01

  So they got together this big review on it and he and his team wrangled up the data, crunched the numbers.

• 40:36Speaker 00

  Yep.

• 40:36Speaker 01

  And the answer to whether or not sun exposure is linked to melanoma in people of color.

• 40:42Speaker 13

  And to sum it up, no, it is not. It is not in anyone that identifies as non-white, not Asian, not Hispanic, not black, right? There is, there is like the almost zero data to support that.

• 41:02Speaker 00

  Whoa. And why is that? Is melanin is super protective for melanoma? What's going on?

• 41:11Speaker 01

  Yeah, so that's also really cool, what's happening there. No matter your skin color, we all have these cells i- in our skin called melanocytes that make the pigment melanin.

• 41:24Speaker 00

  Mm hmm.

• 41:25Speaker 01

  And when we step outside, our melanocytes start pumping out melanin in response to the sun.

• 41:31Speaker 00

  And that's why you tan.

• 41:33Speaker 01

  Yeah, over time you would, you would eventually tan. But before that, like Ade told me that melanin actually like gets packaged up and is like sent, like it, it makes its way toward the surface of your skin.

• 41:45Speaker 13

  I, I don't know if you've ever, uh, noticed a phenomenon in the first, you know, ten, fifteen minutes of some people getting some sun, they make it slightly, you know, darker. That's your melanin, if you have enough at least, that's it moving up around the cell in order to protect the DNA from the incoming, uh, UV exposure. That's like one immediate response.

• 42:06Speaker 00

  Wait, so the melanin sites, the cells that make the melanin, then the melanin is like sunscreen for your DNA, like natural sunscreen for your DNA?

• 42:21Speaker 01

  Yeah, so like this melanin, it's, it's directly responding to the sun, it's moving up there and it's, it's wanting to protect you from those UV rays and in essence protects you from the DNA damage that could cause skin cancer.

• 42:37Speaker 00

  Wow, that's so cool.

• 42:40Speaker 01

  Mm hmm. And yeah, the more, the more melanin that you have in your skin, um, the more likely it's doing a similar job to sunscreen. Here's Ade again.

• 42:50Speaker 13

  So it is helping, you know, ab- absorb some of the harmful effects that the UV will have on the DNA. And, you know, depending on how, um, dark you are, you know, S, you can have, you know, SPF of fifteen plus, um, uh, uh, equivalent at, at least if you're of a darker skin tone.

• 43:11Speaker 00

  That's so cool. So then does.

• 43:13Speaker 01

  Yeah.

• 43:14Speaker 00

  So does this mean if you have a darker skin tone, then wearing sunscreen is not a good idea because then you're at an increased risk of vitamin D deficiency and you don't get this skin cancer benefit? I guess specifically for melanoma, there are other skin cancers to worry about.

• 43:32Speaker 01

  Yeah, so you're right on track. Like after studies like Ade's came out, countries like Australia actually changed their guidance on sunscreen recommendation. So people that are of the darkest skin types don't routinely need to wear sunscreen to prevent skin cancer. They classify it by what's called the Fitzpatrick scale. So there's, uh, six different skin tone types and the two darkest skin tones, um, are not recommended to wear sunscreen for skin cancer in Australia. So I'll, uh, we'll throw that up on screen.

• 44:06Speaker 00

  Aha.

• 44:07Speaker 01

  Um, on the flip side though, places like the US, the American Academy of Dermatology haven't changed their guidelines and this is something that annoys Ade a lot.

• 44:16Speaker 13

  We're not science-based. The recommendation's not. And it's also wild because we're in this era of personalized medicine, right? There should be personalized, uh, risk stratification related to the sun. Anyone saying sunscreen saves lives for a person of color is lying. There's a bald-faced, bald-faced lie.

• 44:42Speaker 00

  Should people of color wear sunscreen then? Does this change the equation?

• 44:46Speaker 01

  Yeah, so I asked Ade and he said that, you know, sunscreen isn't useless, like it still prevents sunburn and could have cosmetic benefits because, uh, we think that melanin better protects against UV B rays versus UVA.

• 45:02Speaker 00

  Mm hmm.

• 45:03Speaker 01

  And UVA rays are the ones that penetrate a little bit deeper into our skin and messes with things like elastin and collagen and can contribute to like an effect of aging.

• 45:14Speaker 00

  Mm hmm, okay, and wrinkles and things like that, aha.

• 45:18Speaker 01

  I asked Ade, like, does he still recommend his patients, who are people of color, to wear sunscreen?

• 45:24Speaker 13

  Sure, I do. Sunscreen has a lot of important, uh, uses. No matter your skin type, you can sunburn, right? That is possible. People like to use it for anti-aging, but you know, for listeners that might not see my image, I'm a black male dermatologist. And so, uh, yeah, I wear sunscreen. I went to the beach like, uh, a few weeks ago, had sunscreen on, you know? I didn't want to get burned, but, uh, do I wear it daily? No, I don't. But that, that's me, that's my, I'm a different risk, say, than somebody that, uh, you know, looks like Pippi Longstocking.

• 46:06Speaker 00

  And I guess if for anyone worried about a vitamin D deficiency, no matter your skin tone, can you just take a supplement if you still wanna wear sunscreen? Is vitamin D supplementation okay?

• 46:24Speaker 01

  Yeah, going back to Rachel Neal, who we heard about with the vitamin D study.

• 46:28Speaker 00

  Mm hmm.

• 46:29Speaker 01

  I asked her, like, can you just take a supplement? And she's like, yes, that's, that's the easy fix to this if you're worried about it.

• 46:36Speaker 00

  Great, okay.

• 46:37Speaker 01

  Now, Rachel herself, she doesn't look like they'd be long socking, but she does have pretty pale skin. And skin cancer is something she's very concerned about. She's also had it before.

• 46:47Speaker 06

  When I brush my teeth, I put my sunscreen on every day. Um, so for me, I think that's really important. We know that that reduces risk of skin cancer, and I've had three. So I had my first skin cancer when I was 29, um, which, you know, shows how problematic the Australian sun can be. And it's the same in other parts of the world as well, where there's a really high UV, which means that just popping outdoors is enough to cause damage.

• 47:13Speaker 00

  All right, is it time for our sunscreen summary?

• 47:17Speaker 01

  Sounds good.

• 47:18Speaker 00

  Okay, so sunscreen does have chemicals in it, obviously. Um, some of them can get into our blood, but as far as we can tell, they're not causing harm while they're there at the doses that they're there. Uh, if you are worried about it, though, you can try mineral sunscreen, which is more likely to stay on the top of your skin and not go into your blood. Sunscreen does increase your risk of having vitamin D deficiency, which is particularly concerning if you have darker skin, you're at a higher risk of that. On the other hand, if you have darker skin, you also don't need to worry so much about

• 47:58Speaker 00

  melanoma, uh, and not great evidence that sunscreen can protect you from that. But if you have lighter skin, then sunscreen is gonna protect you from skin cancer.

• 48:08Speaker 01

  Yeah, you got it.

• 48:09Speaker 00

  I think based on all of this, I'm gonna keep wearing my sunscreen, but I'm gonna start taking a vitamin D supplement.

• 48:20Speaker 01

  Okay, yeah, that's good.

• 48:21Speaker 00

  All right, we got a lightning round, ready to go?

• 48:24Speaker 01

  Yes.

• 48:25Speaker 00

  Lightning round, lightning round, it's where we say some quick facts that can help you in your day.

• 48:32Speaker 00

  We've had a lot of questions about this, just the, the practicalities of sunscreen. If you're still on Team Sunscreen after listening to this episode, here's some tips and tricks about putting it on properly. Okay, when should you wear it?

• 48:48Speaker 01

  Okay, so if you open up your weather app, you will see a section that says UV index, basically telling you, um, how strong the UV rays are that are coming through the atmosphere.

• 49:00Speaker 00

  Okay, weather app, here we go, yeah. All right, so here's what I got, Melbourne, middle of winter, low all day, it's gonna be one.

• 49:11Speaker 01

  So you actually, so like, you need to wear sunscreen if the UV hits three or above. So today, you actually don't need to wear sunscreen.

• 49:19Speaker 00

  Mm hmm. Next question, which SPF should you wear?

• 49:22Speaker 01

  So in Australia, they recommend SPF 50 plus, other places recommend 30 plus. Um, however, the dermatologist I spoke to said you might as well wear 50 because we know from studies that most of us are bad at putting on sunscreen and that we don't put enough of it on.

• 49:38Speaker 00

  Okay, speaking of badly putting on sunscreen, even though I'm mad for it, I shove it on as soon as I leave the house. But I hear you need to put it on 20 minutes before, is that real?

• 49:53Speaker 01

  You do, uh, yeah, it's, it's fascinating because like you actually need time for it to dry and set on your skin. It will adhere a little bit better and then you're kind of like guaranteeing protection.

• 50:04Speaker 00

  Oh, mm hmm. Um, all right, do I need to wear it if I'm behind a window?

• 50:12Speaker 01

  It, it's surprising, like the windows block some of the rays, but let's do a bit of UVA rays.

• 50:20Speaker 00

  Mm, do you know there's a fascinating case report of a guy who was a, a truck driver and for decades would drive, half of his face would be exposed to sun and the other half would be in the shade. And you can, it was published in a scientific journal because you could actually see more wrinkles on the side of his face.

• 50:43Speaker 01

  Yeah, exactly. Yeah, yeah. So those UVA rays are getting through and we know that they're connected with, um, signs of aging and also play like a little bit of role in skin cancer.

• 50:53Speaker 00

  Okay, last question, how much do you actually need to put on?

• 50:56Speaker 01

  So for the whole body, an easy guideline is one full shot glass of sunscreen.

• 51:02Speaker 00

  What about just the face?

• 51:03Speaker 01

  Yeah, so like, let me get out my measuring tool. I'm showing you a teaspoon, a five milliliter teaspoon, which is the same in US and Australia. And, um, the recommendation is one whole teaspoon for your, your face, ears and neck. But for your whole body, you actually want seven of these.

• 51:23Speaker 00

  Thanks, Michelle.

• 51:24Speaker 01

  Thanks, Wendy.

• 51:25Speaker 00

  That's Science Versus. How many citations are in this week's episode?

• 51:29Speaker 01

  There are 92 citations.

• 51:30Speaker 00

  Ooh, and if people wanna see them in all their glory, learn more about the science of sunscreen, where should they go?

• 51:35Speaker 01

  Head over to our transcript that you can find in the show notes.

• 51:39Speaker 00

  This episode was produced by Michelle Dang with help from Merrill Horn, Rose Rimler and Aketi Foster Keys. We're edited by Blythe Terrell, Wendy Zukerman, that's me, I'm the executive producer. Fact checking by Erica Akiko Howard, mix and sound design by Bobby Lord, music written by Bobby Lord, Bumi Hidaka, So Wiley, Emma Munga and Peter Leonard. Science Versus is a Spotify Studios original, you can find us on Spotify, we are also on YouTube, you can like and subscribe. If you liked this episode, please share it with your friends, helps other people know about the science in the world. I'm Wendy Zukerman and I'll back you next time.

• 52:18Speaker 11

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