The Case for Sunshine (with Rowan Jacobsen)

Skin cancer comes from the sun. But so do many good things, according to author Rowan Jacobsen. Jacobsen talks with EconTalk's Russ Roberts about the health benefits of sunshine and makes the case for prudent sun exposure. Topics discussed include the "heliotherapy" movement that peaked in the early 1900s in response to rickets and tuberculosis, why diagnosing skin cancer is on the rise, and why yesterday's sunscreens may have done more harm than good.

• 0:02Speaker 00

  Welcome to Econ Talk, Conversations for the Curious, part of the Library of Economics and Liberty. I'm your host, Russ Roberts of Shalem College in Jerusalem and Stanford University's Hoover Institution. Go to EconTalk.org where you can subscribe, comment on this episode, and find links to other information related to today's conversation. You'll also find our archives with every episode we've done going back to 2006. Our email address is [email protected]. We'd love to hear from you. Today is May 18, 2026, and my guest is author Rowan Jacobsen. He was last here in October

• 0:43Speaker 00

  of 2021, talking about his book Truffle Hound. That episode tied for first place in our annual poll of favorite episodes of the year. His latest book is In Defense of Sunlight: The Surprising Science of Sun Exposure. Rowan, welcome back to Econ Talk.

• 1:00Speaker 01

  Thanks, Russ. Great to be back. I hope I get another first place this year.

• 1:04Speaker 00

  Well, we'll see. You might have to rig the voting like you did the last

• 1:07Speaker 01

  It worked last time.

• 1:08Speaker 00

  Multiple times, yeah. We're going to be talking about a number of issues related to health. I want to remind listeners, we do not dispense medical advice on this show, even though I am a doctor. I'm not the kind that helps people, as we all know. I'm a doctor of philosophy and economics. You should take everything you hear with a grain or more of salt, but this is a very interesting, provocative, and contrarian take on what, for a long time, was received wisdom. So let's get started. What's the central idea of this book, Rowan?

• 1:43Speaker 01

  The basic idea is that we are now at a point where enough science is filled in that we need to reconsider what has been, as you say, the perceived wisdom on sun exposure, that the recommendations we've received for the past few decades no longer accurately reflect what we know about the science.

• 2:10Speaker 00

  And I think most people are taught, you know, depending on what age you are, obviously, but particularly young people are taught that, you know, sun is a killer. It leads to skin cancer, which I think is scientifically undeniable. We'll talk about what kind of nuance we want to bring to that statement when we talk about it more thoughtfully. But the sun's a killer, so stay out of the sun. And if you have to go into the sun, you should cover your body with clothing or sunscreen and protect yourself. That's the received wisdom, I think, for many people, despite the research you're talking about. Is that a... Do you think that's correct?

• 2:50Speaker 01

  Yeah, for sure. And it's actually become more strident that those recommendations over the years. The sun is a killer. We all agree that sun exposure will raise your risk of skin cancer. And so, based on that fact, the authorities have recommended that people first reduce their level of sun exposure and, more recently, pretty much eliminate any sun exposure where your skin is unprotected by either clothing or sunscreen. And that was part of the reason I decided it was time to write the book. What I started to see in the past few years, that the typical advice you'd see in the

• 3:31Speaker 01

  media was, you know, stay out of the sun, summer, winter, no matter who you are, no matter what your situation is, use sunscreen, even if you are going to be indoors all day and it's winter. And that didn't reflect what the researchers had been discovering for a few decades.

• 3:52Speaker 00

  And I think I would sum up the lesson of this book, and for, you know, like your previous book, this is a very readable book. There is a lot of science, but it's written very, very clearly. I would sum up, one summary sentence would be, "The sun is not bad for you. In fact, it's good for you. It does have costs, potentially, and thoughtful people should be aware of those trade-offs." Is that a fair summary?

• 4:20Speaker 01

  Yeah. You know, when you said the sun is a killer, I, you know, I almost had to, wanted to, like, jump in and say, "Well, it is, but it's also, you know, a giver of health and vitality." And that part has been left out of the equation for a while.

• 4:39Speaker 01

  The sun, we'll get into this, but the sun improves. We now have pretty solid evidence that, you know, moderate sun exposure improves health in lots of, both direct and indirect ways. And that was what was left out of the equation when we were told the sun is a killer. It raises your risk of skin cancer. That's true, but that's obviously a very small portion of overall health and longevity. And so I, there's a metaphor that some of the researchers use, which is that it's kind of like if orthopedists started telling people, stop exercising because when you exercise, your risk of knee injuries goes way up, right?

• 5:21Speaker 01

  We're seeing a lot of knee injuries from exercise, therefore never run. In fact, don't even walk around if you can help it, just sit down because that way that's going to take the pressure off your knees. And they weren't taking into consideration these other pieces of the picture. That's kind of what's happened with sunlight.

• 5:38Speaker 00

  And before I read your book, I would have said, you know, maybe I could imagine that there's some evidence that sunlight's good for your disposition, your mood.

• 5:48Speaker 01

  Right.

• 5:48Speaker 00

  People say, you know, get out early in the morning, get some sunlight, it'll make you feel better, you know, and we all know, and you write about it at the very beginning of your book, that if you live in a climate where the sun doesn't shine very often, it can be, winter can be very dark, literally, but also emotionally. Yet what I'd say the most powerful parts, you talk about that, that's very interesting. But the most powerful parts of this book is the possible role that scientists are discovering for sunlight with the health of our skin, possibly the health of our heart, our autoimmune system. And I have to confess, being a skeptical person, when I hear it stated that way, it

• 6:30Speaker 00

  sounds a little bit rah rah as a contrarian take on this issue, which has gone so far in one direction, you're going so far in the other. And yet the science is quite, quite serious. This is not, this is not quackery or a study found a small sample. It's really quite, there's a huge amount of research on this, it sounds like.

• 6:56Speaker 01

  And that's partly what drew me into it and made me want to really devote myself to a book-length work on it. Yeah, there's actually decades of science in multiple different fields that have been discovering these benefits of sunlight. And they really haven't come into the public discussion. And it's just how science works. There's a lot of specialization in science. These researchers would publish their study and they'd say, "Well, it looks kind of like sun exposure might be good for you in this case." But it wasn't their job to take it any farther than that. So the papers get

• 7:35Speaker 01

  published and they kind of just disappear. So, once I started seeing so many of them out there and realized there was kind of nobody whose job it was to bring it all together and try to synthesize that into some sort of overall understanding of what was going on, it seems like that was a pretty good way to focus my time and energy. And it is, like, you're right to be skeptical. I was skeptical at first, too. Anytime you hear something that really diverges from the recommendations of the experts in the

• 8:19Speaker 01

  field, you immediately wonder about quacks and where the information is coming from. And so it's great to be skeptical. And one of the things I'm hoping this book does is just bring that conversation into the general discussion, rather than try to make a slam dunk case for it.

• 8:38Speaker 00

  And I would just add, of course, we should be skeptical sometimes of the advice of the so-called experts. Because as you point out, the sunscreen industry is a very large one. There's a lot of money to be made. Dermatologists make a lot of money removing things on the skin that may or may not be harmful to us. So you have to be balanced. You have to be thoughtful. And of course, the world's complicated, as we know, as listeners on this program know. But I want to start, one of the things that's fun about this book is the narrative arc.

• 9:10Speaker 00

  Of how people think about and have thought about sunlight. So there was this period, which is really fascinating. In the early 20th century, I think, is the time period, but it goes back, I think, into the 19th as well. When people had this incredible romance about the healing powers of the sun. And the phrase that was used is heliotherapy. Helio is related to the sun. So being on the sun is good for you. And this was part of a movement. So talk about how that movement started in fighting, say, tuberculosis and other really serious things where sunlight did help.

• 9:52Speaker 00

  And but then the sort of obsession with it, especially in California and elsewhere.

• 9:58Speaker 01

  Yeah, it's a fascinating history that I wasn't really familiar with until I dived into the book. And I think we've mostly forgotten about it. But yeah, we had this amazing era of heliotherapy in both Europe and the United States and really peaking in the early 1900s. And as you mentioned, it really all came out of tuberculosis, yeah, to a large degree. Now tuberculosis is still a big, like, if you look at mortality figures worldwide, tuberculosis is still a big player. But back in the 1900s, it was a massive, sorry, the 19th century, it was a huge problem.

• 10:38Speaker 01

  I think one out of every four deaths in Europe was due to tuberculosis in the later 1800s. And a scientist from the Faroe Islands, of all places, was the first to realize that cutaneous tuberculosis, tuberculosis can kind of like go in two different directions. It can either infect the lungs, which is sort of the classic consumption of like, you know, romantic poetry. Or it can be cutaneous, it can affect the skin and just like eat flesh. And they're both really bad, or they were before antibiotics. Anyway, this.

• 11:21Speaker 01

  Faroe Islands doctor named Finson discovered that concentrated sunlight could kill the cutaneous tuberculosis and could cure cutaneous tuberculosis. And that became a big deal. At the same time, doctors were discovering that another disease that had sort of popped up in the Industrial Revolution, rickets, was caused by lack of sunlight. All the kids in tenements in the UK and elsewhere, who were never exposed to the amount of sunlight they would have back in the farming days, were coming down with rickets, which is a terrible disease. Your bones never get hard as a kid, so you get bowed legs and deformed skulls.

• 12:05Speaker 01

  It was also a big problem in this era. That also turned out to be cured by vitamin D, and they discovered that it was sunlight hitting skin that produced vitamin D. So suddenly, two of the major diseases of that 1800s period, rickets and tuberculosis, were being fixed by sunlight. And there were clinics popping up everywhere to do so. And it became, it came to be known as heliotherapy. And, you know, people would go up to the Swiss Alps, where the light was really good, to the sanitariums up there, to take the light. Like, we, you know, we know that era of like the Magic Mountain, where people would go

• 12:49Speaker 01

  up to the Alps, to the sanitariums for the fresh air. But fresh air was only part of it. The light, the quality of the light was the other part of it. And so, once people started thinking about light as a thing that could cure these diseases, they did go a little too far, and they began asking like, well, you know, what else might light cure? And doctors kind of started noticing that people who got a lot of light and fresh air tended to be healthier than, than people who didn't. So then, you can see through the 20s, 30s, the top medical experts of the time, all really like getting on board the light train and saying like,

• 13:31Speaker 01

  One of the keys to public health is that everybody gets light and schools were redesigned to make sure that kids got more light. The kids would be sent out to play in their underwear. It was really this crazy, crazy era. There's spectacular photos from this time, like in Switzerland, of kids just in their boxer shorts, sitting in the snow at their desks, taking their lessons, and instructors also in their boxer shorts, instructing the kids. It was pretty incredible. And everybody was on board with it until, you know, until the 30s and 40s, the first inklings that all that light might also be causing skin cancer began to

• 14:13Speaker 01

  like appear, at which point, things started to flip in the other direction.

• 14:18Speaker 00

  Let's talk about the prevalence of skin cancer and then we'll come back to vitamin D in a little bit because it fascinates me. But let's talk about skin cancer. So, skin cancer surges probably worldwide, but certainly in the United States. And you'll have a better, give us a better idea of exactly the timing of that. But it's, it's a little complicated by some, the kind of usual factors people often ignore when they worry about an increase in, in a disease. So, or in terms of diagnoses of a disease. So, talk about the actual, what we know about the history and why it's a little more complicated maybe than it first appears. And the two different kinds of skin cancer, two different kinds of cancers that,

• 15:03Speaker 00

  that are, that are relevant here.

• 15:05Speaker 01

  Yeah, it's, skin cancer, you can kind of, there's three major types of skin cancer. One is squamous cell carcinoma, and one is basal cell carcinoma, and those often get referred to as SCCs and BCCs. And those are responsible for about 98% of all skin cancer cases. Then, the third important type of skin cancer is melanoma, and that's more like 2% of, of skin cancer cases.

• 15:34Speaker 01

  And I'm sure we'll dive into this later. Melanoma is the one you really want to worry about that has, you know, there's significant mortality associated with it. The SECs and the BCCs are the ones, you know, everybody you know tends to get after they hit age 70 or 80. And they, you know, you have to cut them off because they'll keep getting bigger, but they very rarely become invasive. So they're not associated with significant mortality in any way. Weirdly, none of those diseases were very prevalent before about World War II. Like, back in the day, in the, you know, the early 1900s, skin cancer was something that sailors got.

• 16:19Speaker 01

  Sailors get a ton of sun exposure. They also get terrible diets, and your diet does affect your risk for skin cancer. So sailors, maybe, you know, the occasional farmer would get a skin cancer, but it was not on doctors' radar at all. And then somewhere around World War II, numbers go way up. And partly, as you're referring to, it was partly just a demographics issue. As public health gets better and people don't die of cardiovascular disease or infectious disease at earlier ages, they live long enough to get skin cancer. And not just skin cancer.

• 17:00Speaker 01

  You see this funny, confounding trend in, like, lots of different areas where, as public health improves, rates of cancer go up per 100,000 people because people are living long enough to get cancer. That's, you gotta die of something, right? So cancer rates tend to go up when other things improve. But then you look at the age-adjusted numbers, and maybe they're not going up as much as you thought they were. But so, yeah, what happened in the second half of the 20th century in the US and Western Europe is that people were living longer.

• 17:42Speaker 01

  But skin cancer cases were exploding, like even more so than could be accounted for by longer life. So that was when this sort of panic started to set in that we were, some sort of epidemic was underway and it had to be sunlight because we, you know, shown in lab tests that if you zap a mouse with enough UV, you can create skin cancers on it. So basically, doctors assumed that the entire rise of skin cancer was because people were being irresponsible and were exposing themselves to a ton more solar radiation

• 18:23Speaker 01

  than they used to back in the day. And so that's when the messaging started and then eventually got more strident that you need to stay out of the sun.

• 18:32Speaker 00

  That's not a very plausible explanation because over the course of the 20th century, people spent more time inside than they had before. You know, we have the rise of offices, the farming goes from 40% of the workforce in 1900 to 3% by the end of the century. So people aren't in the sun. There aren't many sailors left in the world as a profession. It's not a common profession. It's there are other forms of transportation. So they had to have, there has to be another explanation. And of course, the other usual challenge in these kind of trends, and I won't name particular diseases, but a lot of times people

• 19:15Speaker 00

  worry about some epidemic in a disease and they assume that epidemic is real, when sometimes it's merely an increase in diagnosis. So I don't know when dermatologists were invented. Seriously, as a subspecial, as a specialty, but that had, I would guess, something to do with this. So talk about the diagnosis issue. I mean, just to give an example, I had an issue, I forget, I don't need to share with listeners, but I had a skin issue. It would have to be on my face and I went into, my doctor was concerned about it. I went to a dermatologist. Dermatologist did a full body check, make sure my entire skin was free of things. Of course, it's not. It's got spots, skin tags, other, you know, exciting

• 20:03Speaker 00

  Irregularities, most of us do, I suspect, I don't think it's just me. But once you have that process in place, you are going to discover more things. Now, the question is whether human health has deteriorated. And in theory, discovering more things early could be good because then you could treat them. So you'd want to see if the treatment of it was leading to longer, to longevity and lower rates of mortality. So talk about what we know about that.

• 20:31Speaker 01

  Okay, I'm gonna, I'm gonna lead in with a fun, a fun fact. What's the number one best predictor of whether you will be diagnosed with skin cancer in the US? It's not sun exposure, I'll, I'll, I'll give you that one for free. It's

• 20:50Speaker 00

  Go ahead.

• 20:51Speaker 01

  How many dermatologists there are in your county and, and the overall age bracket for people in your county. And that, that is to your point about diagnosis. The, the more you look for something, the more you're going to find it. And a huge amount of the rise in skin cancer cases is because we're looking a lot more carefully. Now, that's not a bad thing, right? If you're, you're finding skin cancers that might maybe got missed before and never diagnosed, never even made it into the records. That's a good thing, and that's definitely been one thing that's happened.

• 21:27Speaker 00

  You're finding them earlier, ideally it can be treated more effectively when it's early.

• 21:32Speaker 01

  Right, that's all, all to the good. As, as long as you don't start to panic because you're, now that you're looking, you're finding a lot more and, and think that some, something has changed that needs to be dealt with. And, yeah, as you said earlier, you, you look back at some of the, like, some of these early papers about the rise in skin cancer. And it is almost laughable how bad some of the reasoning was. Like, the earliest, in the US, the earliest, like, solid data on, on skin cancer was like this Connecticut registry in the 40s. For whatever reason, Connecticut started doing it a little bit before any other state.

• 22:11Speaker 01

  So to, to compare rates of skin cancer today and commit to Connecticut in the 40s. The researchers literally assumed that back then, in the 30s and 40s. Nobody ever exposed their skin to the sun. Like, you can actually read these lines in the papers and go, what are they talking about? Have they looked at photos of people on the beach in the 30s and 40s? But the idea was that, back then, people were much more conservative. They never spent any time in the sun.

• 22:43Speaker 01

  So the entire rise in skin cancers is because now we are spending so much more time in the sun.

• 22:48Speaker 00

  And we should add, there is a cultural interest in tanning and bronzing and having a tan. You could argue was, when we were talking about what changed, it's true. I overstated the case. I said, people don't work as much outside in the last half of the 20th century as they did in the first half. On the other hand, they didn't have much leisure in the earliest parts of the 20th century. They didn't have time to go to the beach and lay in the sun and bake for X hours. And it could be that that's the cause.

• 23:22Speaker 01

  Right, and I've actually looked for good numbers on time spent outdoors. And it doesn't, unfortunately, it doesn't really exist. The best numbers you see are for kids. Like, there's some studies that have tracked kids' outdoor time over the decades. And you see, unsurprisingly, a gradual decline per decade from, you know, a few hours per day back in the 40s or 50s. You know, when I was a kid in the 70s and 80s, after school, we would be outdoors playing all the time. Now, there's a lot more indoor time and kids get like less than an hour per day.

• 24:02Speaker 01

  So we know with kids that there's been a gradual, significant decline in amount of time spent outdoors. I think we generally assume that it's true for adults as well. Like, people spend a lot more time indoors on screens than they used to. But there isn't any real solid data about how much time we're getting outside.

• 24:21Speaker 00

  But is it fair to say that this explosion in skin cancer rates, which are often not distinguished between carcinoma and melanoma, one not as dangerous, one very not good, melanoma? Is it fair to say that that rise is mostly due to increased attention from dermatologists who categorize blemishes unnecessarily perhaps?

• 24:50Speaker 00

  What do we know about, and was it good? Was, as you said, it could have been good to find more of these. What do we know about the all, you know, the mortality rate from, deaths from skin cancer, which is what we really care about?

• 25:04Speaker 01

  Right, and this has been looked at most closely with melanoma. And there's been a lot of discussion in the research community about overdiagnosis with melanoma.

• 25:15Speaker 01

  Everyone agrees that overdiagnosis is going on, but again, maybe it's not that much of a problem because you want to make sure you catch them all, right? You want to err on the side of taking off anything that might be problematic down the line. Actually, one thing that we should mention is that until a melanoma becomes invasive, we don't actually have any solid way of predicting whether it's going to be a problem or not. Like, so all the ones that are caught very early on the skin and are called melanomas, they might be fine, but obviously, you know, if a doctor says to a patient, like, "It might be fine, or it might not.

• 26:01Speaker 01

  Do you want me to leave it?" Like, no, you're going to get it cut off. So, all these things that get called melanomas and get cut off, and everyone agrees that some of them would not have been called melanomas back in the day. And there was actually a really interesting study a few years ago where they took slides of, you know, lesions that had been called melanomas 20 years ago, or lesions that might or might not be called melanomas. And they took the exact same slides that had been done 20 years ago and showed them to a group of dermatologists 20 years later, including actually some of the same dermatologists who saw the slides 20 years earlier, and asked them to make the call, melanoma or not melanoma.

• 26:47Speaker 01

  And 20 years ago, 11 were called, were judged to be melanomas. And today, the exact same slides, 18 of them were judged to be melanomas. So we're getting more lenient on what we call melanomas. And like we said, that's not necessarily a bad thing. But that is definitely a big factor in the rise of melanoma incidence. Because when you look at mortality in melanoma, there's been no change. Decade after decade after decade, mortality is totally flat, while incidence is rising steeply. And as some scientists have pointed out, that's kind of like, like the classic sign of overdiagnosis.

• 27:26Speaker 00

  But it could just be that we're better at treating it, and it's good that we're catching it early. It would have been worse otherwise. And I think the real, the puzzle here, and you go into it in some complexity in the book, and in a thoughtful way, is that somewhere along the line, and you will tell me when, sunscreen gets invented. And sunscreen, it's a pretty modern creation. You know, in ancient times, sunscreen was called going inside, or sitting under a tree, or putting your shirt on, right? There are many ways to screen out the sun that don't require a pasty, coconut-flavored chemical.

• 28:08Speaker 00

  But at some point, that industry was born as a way to allow people to expose them parts of their body and be outside, and even possibly get darker and more, in theory, more attractive by getting a tan. And that's really complicated, and we're going to talk a little bit about it, because I think it's really interesting. But this rise in skin cancer is coincident with the enormous expansion of the sunscreen industry, which is surprising, right? All of a sudden, we have this special way to keep the harmful rays of the sun from hurting us. And yet, at the same time, when people are using a whole lot more of it than they did, either because it hadn't been invented yet, or it just wasn't that available, or people

• 28:53Speaker 00

  didn't know much about it, all of a sudden, everybody knows about it. It's everywhere, in all kinds of different levels, and we'll talk about SPF in a little bit. But, I hope, but...

• 29:04Speaker 00

  Why wouldn't that have ended this epidemic? Why didn't the creation of sunscreen, which I think used to be called in my days suntan lotion, but sunscreen, which sounds more scientific, why didn't that end this problem?

• 29:20Speaker 01

  So this is an inconvenient truth that has been sort of lurking in the background and dogging the industry for a long time. Yeah, rates of skin cancer and rates of sunscreen use track each other spectacularly well. Like decade after decade, sunscreen sales through the roof compared to what they used to be, and yet rates of skin cancer also go up. And all the epidemiological studies tend to show that more sunscreen use is correlated with more skin cancer, which was also an inconvenient truth, except you look at it and you're like, well, that's fine, because who's using sunscreen?

• 30:03Speaker 01

  People who have paler skin, who might need it more.

• 30:06Speaker 00

  Go out more, yeah.

• 30:07Speaker 01

  People who are out in the sun. So that's, you know, that's also, it can be a little awkward.

• 30:11Speaker 00

  Classic reverse causation, right?

• 30:13Speaker 01

  Classic reverse causation, exactly. But it sure as heck hasn't been helping as much as we might have been led to believe that it would. That's clear. That, you know, SPF rates have gone up, adoption has gone up, people are using more, people are avoiding the sun more. It's not turning skin cancer cases around at all. So clearly, there's more to the story than pure exposure to sunlight.

• 30:42Speaker 00

  Let's talk a little bit about, I mean, it's complicated, but talk a little bit about, so first SPF, is that sun protection factor?

• 30:52Speaker 01

  It is.

• 30:53Speaker 00

  So this is a startling thing I learned from this, from your book, which is... An SPF of 15 and 30, I just thought they were numbers that meant more protection. They actually have a technical meaning, which is good because SPF sounds like science. It should be, you know, sigma pi, whatever F is. Is there a Greek letter for F? Phi. It should sound more scientific even that way. But when you say SPF-15, it looks scientific. Explain where those numbers come from and why it's not as comforting as you might think. And why SPF 60, which we'd be like, oh, well, that's better. Why it's a little complicated.

• 31:34Speaker 01

  Right. It's almost like extra strength, you know, Tylenol, like the bigger number seems like we're helping ourselves more. So SPF, that factor is how many more times you can stay out in the sun when you're using it without burning until you burn than you could if you had nothing on. So if you can stay in the sun for 10 minutes before you started to burn with nothing and you put SPF 20 on your body, you can stay in the sun for 200 minutes before you got the same amount of burn going on. And then so SPF 50, you can stay out in the sun 50 times as long before you start to burn.

• 32:18Speaker 01

  That's originally FDA wasn't even going to let the industry use anything like SPF 50 because nobody should be staying in the sun that long. But basically, that's a measure of what percentage of the ultraviolet light it's blocking. And it's important to understand that sunburns are caused by UVB. We divide the ultraviolet light spectrum into UVA and UVB, and they actually have very different effects on the body. And UVB was the first one we worried about. It was also the only one that the original sunscreens were able to block. So those first sunscreens focused purely on UVB, which turned out to be a big problem.

• 33:01Speaker 01

  And SPF only applies to UVB. So you could have a sunscreen that's SPF 50, which means it will block

• 33:12Speaker 01

  UVB, 50 times as well as nothing, meaning basically it's blocking 98% of the rays. Only 2% of the UVB rays are getting through the skin. That doesn't mean it's blocking UVA at all necessarily. And that was a problem in the old sunscreens that we all were using in the 70s and 80s before what they called the broad spectrum or full spectrum sunscreens came on the market later.

• 33:39Speaker 00

  So in theory, one explanation for why sunscreen didn't have much impact is that it wasn't really doing what we hoped it would do, blocking the harmful part of the sunlight. But in theory, the improvements in those formulations should have made a difference.

• 33:56Speaker 01

  And it looks like they, yes, and it looks like they did. And the new sunscreens are way better now than those sunscreens were a generation ago. And actually, starting next year, we're going to get even better ones on the market, it looks like. The sunscreens are used in Europe and Asia and Israel are much better than the ones that are allowed in the US. We can get into why, but the US ones are a generation behind, basically. And yeah, they used to only block UVB because originally we thought UVB was what caused skin cancer.

• 34:39Speaker 01

  UVB is what causes sunburns. And yeah, those early, they weren't sunscreens, they were sun tanning aids. The whole point was to keep you from burning so you could stay in the sun longer so you could get even more bronze, right? And then they sort of pivoted to a health aid later on. But they were only blocking UVB because at the time, the doctors thought that UVA was not a problem. Like UVB, we knew it could, it had enough energy in those light photons that if it hit a DNA molecule in your skin, it could actually mess up the DNA and give you skin cancer. So we thought we had to block those UVBs.

• 35:22Speaker 01

  And the original ingredients that were used in sunscreen, those chemical filters, were able to do that. So it seemed serendipitous, right? Block the sunburn, block the UVB, so you're not going to get skin cancer, let the UVA through, and you're going to get tan from that. Perfect.

• 35:43Speaker 01

  By the 80s and definitely by the 90s, everyone was realizing that UVA was actually indirectly causing skin cancer as well, and was probably a bigger problem than UVB all along. Which suddenly made those sunscreens look terrible, like possibly worse than nothing, because by blocking sunburn and making you think you were safe from skin cancer, they were allowing you to stay in the sun, depending on the SPF, 10, 15, 20, 30 times longer. At all of that time, gobs of UVA was pouring into your body and probably contributing to melanoma, we now know.

• 36:26Speaker 00

  That's part of the problem.

• 36:29Speaker 01

  I think it's actually a huge problem, and it's kind of been swept under the rug a little bit. Like, now mostly broad-spectrum sunscreens are on the market, and frankly, no sunscreen that doesn't block UVB and UVA should even be allowed on the market, I don't think. And they've gotten much better. And you see that, like, in all the observational studies that track sunscreen use and skin cancer, the early ones, from like the 70s, show no effect and often, you know, reverse effect, like, it was worse to use the sunscreens. By the 80s and 90s, it's looking like, you know, an even wash.

• 37:12Speaker 01

  And now, the more modern ones, it's starting to look better for sunscreen now. So, I think the new ones are pretty good. I think they can be a very useful part of any sun program that you want to develop. And they're going to get better still in the US, and they've been better for a while in most of the rest of the world.

• 37:30Speaker 00

  So, let's talk about vitamin D. I think we've talked about my vitamin D issues on the program in the past.

• 37:37Speaker 01

  Yeah.

• 37:38Speaker 00

  I'm always ready to... Sacrifice my body for science for my listeners. You know, you go to the doctor for a physical, and this has probably been true for, I'm 71, but I suspect it's been true for 30, at least 30 years. You go in my life, I go to the doctor, I get a bunch, I take, uh, blood is drawn. Uh, I get a bunch of other tests, and when they draw my blood, they tell me I'm vitamin D deficient. And then they say, most Americans are because we work indoors and we don't get much sun. And I said at the beginning of this program, of our conversation, that if you'd asked me what's good about the sun, I would have said, well, it's, you know, it's good for your, your mental health. It's good, it makes you in a better mood, you don't get blue in the winter.

• 38:22Speaker 00

  But of course, there is this other thing I forgot to mention, which is vitamin D. And vitamin D is not a small thing. It's kind of important. And my position, um, don't take this as medical advice, folks. Listen, you know, um, Rowan will, will chime in with his view, but my position's always been, it's not obvious that taking an enormous supplement of, of vitamin D in the form of a pill, which raises your vitamin D score, actually achieves the things you would get from an organic, uh, increase in vitamin D from being out in the sun more, which are stronger bones, other things, I think reduced risk of shingles and, and it really, it's not a small thing. It's kind of really important.

• 39:06Speaker 00

  So you shouldn't ignore, uh, vitamin D deficiency. But when my doctor would say, take this pill, I would say, well, I look at the side effects, which include things I'm not going to mention because maybe they're not true. So I don't want to mention, but I would say, well, I look at the side effects. It's not obvious to me that this is a good trade off, especially since I'm not convinced that raising my score is the same as reducing my risk of, say, shingles or bad bones. Uh, what do we know about this?

• 39:36Speaker 01

  Yeah, it is starting to look a little bit like it's like cheating on the test, basically, to take the pill. Like, it's not doing the thing that was the goal all along. But it took us a while to get to that point. Back in the 1980s, it started to look like vitamin D was really important to health because, again, of all this observational data where you look at populations and the group that has low vitamin D levels has higher rates of every disease you can think of across the board: cancer, cardiovascular diseases, autoimmune diseases, Alzheimer's, other types of dementia, diabetes, you name it.

• 40:19Speaker 01

  Low vitamin D looked, it was associated, at least, with all of these different things. Correlated. Yeah, yeah. So, it seemed like, and then, you know, the mechanistic studies in the lab would also show that, you know, you add more vitamin D to these cells and it prevents cells from going cancerous and improves membranes. What we do originally that it helps mineralization in the bones, so you get strong bones from vitamin D, like going back to the Ricketts days. Anyway, it looked like there were reasons to think

• 41:01Speaker 01

  that it really was like kind of a wonder drug that could help all these conditions. But, you know, by then, by the 1980s, we were also like really worried about skin cancer, so doctors weren't about to say, "Go out and expose your skin to sunlight," which is the natural way to make vitamin D. So everyone, you know, started recommending supplementation.

• 41:26Speaker 01

  And...

• 41:28Speaker 01

  People did it, like it's the most prescribed supplement in the world, I believe. And there have been huge, really rigorous, high-powered clinical trials where half the people get vitamin D pills and half the people get placebos that, you know, and they're tracked for years because it seemed like, you know, it was worth putting all that money into these trials because this really did look like a wonder drug. They have completely failed across the board where we know that unless you are extremely vitamin D deficient, raising your, the amount in your blood through a pill doesn't help with any of these conditions. And there's even been, you know, like the editors of the New England Journal of Medicine have published editorials saying, "Stop prescribing vitamin D pills.

• 42:12Speaker 01

  It's not, not helping." But it hasn't, that, that hasn't happened. It's still the most prescribed supplement. I think doctors, some doctors know that it doesn't do much, but, you know, it doesn't hurt. Like it makes their patients feel better and placebos are not nothing. Some doctors probably don't, haven't looked at some of the research. But yeah, so there's the conundrum, like people who naturally have high levels of D in their, in their body have lower rates of all these diseases. People who artificially raise the level in their blood through a pill, it doesn't help at all. So how can that be?

• 42:46Speaker 00

  So the real question, of course, that we all care about is if I spend more time in the sun and raise my measured vitamin D, will that help? And, right? In other words, all the, many times the challenge of these studies, these observational studies in epidemiology, which are, in my view, a cesspool, intellectual cesspool, to use a phrase. The question is, what, what happens if you, an individual, then becomes one of the people who looks like those other healthy people because you now have more vitamin D on your score, but you don't have the other factors that we haven't controlled for, whether it's

• 43:28Speaker 00

  where you live, your latitude, your diet, your income, your genetics, et cetera, et cetera. So there's always a question whether this is, is, is real. In response, my doctor wanted me to supplement. I said, no, I said, give me a shot. I'm going to spend more time in the sun. Uh, I asked Claude, I told Claude, I live in Israel. Israel's very sunny, uh, a huge portion of the year. Uh, and, um, it's at a particular latitude, uh, which is not as sunny as some, the, the intensity of it is not as intense as some, but more intense than other places. And I gave it my age and, you know, where you catch the sun, if you roll up your shirt

• 44:10Speaker 00

  sleeves or go without a hat or whatever, you know, which is not ideally for other reasons. Uh, you know, how much, how much is going to help? The answer is not a lot. It's really hard when you're 70 something years old. Your body doesn't make vitamin D as well as it used to from sunlight. The, the machinery, the factory is, is, is sluggish. Uh, by the time, if you do it at nine in the morning, when I like to have eight 30 or eight 15, when I want to have my coffee with my wife on our porch that gets sunlight, yeah, it's not so intense at eight 15, you really need to do it between one and three, but I don't really need, I can't really afford to be out in the sun. I'm working and so on.

• 44:48Speaker 00

  So, however, I got my score very into, into a range that made my doctor happy. Uh, but of course I risk, I raised my risk of skin cancer. So these are the trade offs that mature adults need to face. And I want you to talk about some of the factors that might also weigh in on that, like where you live, like your skin complexion, like how often you're out in the sun, et cetera, et cetera. Uh, it's complicated, but, but there's some things we can probably think about thoughtfully rather than just never go in the sun or go out in the sun all the time and get your vitamin D up to a million.

• 45:31Speaker 01

  Yeah, exactly. And, you know, moderation, once again, is going to end up being the, the best policy here. You mentioned like, once, once you're 70, it's harder to make, uh, vitamin D. And yeah, that's important. I was just looking at some numbers on this. Basically, yeah, by the time we're 70, we're on, we're only producing half as much vitamin D for the same amount of sunlight as when we're, you know, in our 30s. So. Yeah, and there's no, there's no good, good, but on that, it's just, it just kinda sucks.

• 46:03Speaker 00

  The way it is. It's life. So a lot of things that decline after 70, trust me. That is not the only thing that gets more challenging when yours, your vitamin D production is not the most, the biggest thing to worry about.

• 46:16Speaker 01

  Wisdom, however, way up.

• 46:18Speaker 00

  Way up.

• 46:19Speaker 01

  Right, so.

• 46:19Speaker 00

  Way up.

• 46:23Speaker 01

  But so part of the, like, one of the questions with the whole vitamin D story is whether vitamin D was actually responsible for all those health benefits in the people that were getting more sunlight, or whether it was just sort of a long for the ride. You know, it was, it was an indicator of sun exposure, but it wasn't the agent that was bringing the good health necessarily. There could be other things about sunlight. So even if you're 70, you're not making vitamin D like you used to, you probably are still getting some of these benefits of sunlight from other things, which we can, we can talk about.

• 46:58Speaker 00

  We will. Well, in a minute, I want to come to that next, but continue your thought about that trade off of whatever the benefits are of sunlight, vitamin D and the other things we'll share in a minute.

• 47:11Speaker 00

  Is it, is it worth it? Right? That's the question a person has to always ask. And in the world we live in today, the answer is never. That's, that's why I like your book. I, I'm not going to say your book is, that everything in it is true and listeners should, should ignore the risks of skin cancer. That would be stupid. You don't say it either. But overwhelmingly, the, the sun is poison in, in our minds. This, this, this narrative has become extremely well entrenched. It's a death, it's death. It's skin cancer. It's death. Vitamin D, okay, fine. Maybe it's, it's a little, it's good for some things. You should supplement. Okay. Well, turn does, doesn't work so well. So what do you do now?

• 47:54Speaker 00

  Should you, should you go out in the sun if you're, forget 71, if you're 51, 21, 11?

• 48:02Speaker 01

  Yeah, so the trade-off question is the right question to ask. And the first person I ever saw ask that question was a dermatologist in Scotland named Richard Weller, who had done some research that showed that when sunlight hits skin, it produces nitric oxide in the skin. And nitric oxide is a well-known vasodilator. It allows blood vessels to expand and lowers blood pressure because of it. It's used in a lot of heart medications. Even Viagra is based on nitric oxide. It lets more blood flow.

• 48:42Speaker 01

  So his studies had shown that shining, like the equivalent of like 20, 25 minutes of summer sunlight on volunteers, his grad students, just shining it on their arm would lower their blood pressure. It raised nitric oxide in their blood. It produced nitric oxide in the skin. That nitric oxide went into the circulatory system and lowered blood pressure by like five or six points, which would be enough like worldwide to reduce deaths from heart disease by like a million people or something. So he was the first person to ask that trade-off question.

• 49:26Speaker 01

  He ended up doing a TED Talk, which you can still find out there.

• 49:30Speaker 00

  We'll link to it.

• 49:31Speaker 01

  And the reason he wanted to ask the trade-off question was because skin cancer, we hear a lot about it, but it doesn't actually kill very many people. It's not a significant cause of mortality. In the US, it causes, you know, about 10,000 people a year die from skin cancer. And that's not nothing. If we could get 10,000 to go to zero, that'd be great. But cardiovascular disease is, you know, closer to a million people and cancer is like maybe 600,000 people. So those are the biggies. And diabetes is another big one and infectious disease. So skin cancer is like worldwide is, you know, it's not even...

• 50:17Speaker 01

  On the charts in terms of mortality. It's not one of the top 40 causes of death in the world. So if sunlight would slightly raise the risk of skin cancer, but would slightly lower the risk of cardiovascular disease alone, that would be a massive win in terms of the trade off. And I didn't get this new study in the book, but Weller and his group just came out with a new preprint a few months ago that looked more specifically at the trade off question. And to do so, they used the UK Biobank,

• 50:55Speaker 01

  which is this fantastic data set that more and more researchers are using. And what happened is back in the early 2000s, there was this push to create an incredible health data set in the UK. So they got 500,000 volunteers in the mix, took every health metric they could, questionnaires, got every possible granular detail about these people's health. And they were all ages 40 to 69. So they were all sort of like middle aged. And then they've been tracking that group of 500,000 people ever since. So we now have about 20 years of data on them.

• 51:39Speaker 01

  And it's such a rich source of data that even though observational data can be intellectual cesspool, this is a pretty good one, right? So you can get away from some of the problems if you're using small data sets. And so Weller took a look at that group. And you have location data for all of them. And some of them have even had their sun exposure tracked. But even if you haven't attached a light sensing wristwatch to the volunteers, you can check the satellite data for their location and get a pretty good sense of how much light they've been exposed to on average.

• 52:25Speaker 01

  So he just published a preprint that tracked this group, like I think they had 420,000 people ultimately in their study, mortality and incidence of disease against sun exposure. And they didn't just do sun exposure, they also asked the people about sun habits, like did they seek sun, did they actively try to get some sunlight. So they scored everyone for like a sun seeking habit and tracked that against disease. And what

• 53:05Speaker 01

  they found was that of the 420,000 people, about 45,000 had died, period. Almost all cardiovascular disease and cancer were responsible for most of those diseases. Only 440 had died of melanoma, only 60 had died of other skin cancers out of 420,000 people. So skin cancer doesn't kill very many people. And what they found was that, yes, if you, the people who got a lot of sun versus a little sun were about 20% more likely to die of melanoma. The people who got a whole lot of sun were actually no more likely to die

• 53:50Speaker 01

  of melanoma. But so there was a slight rise in melanoma deaths for the high sun people. But that amounted to, you know, like, less than 100 people overall, over 20 years in this set of 420,000 people. Meanwhile, they were far less likely to die from cardiovascular disease or cancer and some other diseases that contributed minor numbers. So I think the ratio was 75 to 1, that more light

• 54:25Speaker 01

  For every one extra death from melanoma that it created was saving about 75 deaths from other bigger, more problematic diseases.

• 54:36Speaker 00

  And to have a lot of confidence in that, you'd want to know more about the connection between sunlight and those diseases, the nitric oxide is at least a mechanism. Is it plausible of that magnitude? You have to look into that. You have to make sure you're controlled for income and other factors. I'm sure they tried and how well they did it. It could be that rich people have lots of, tend to have better health than poor people and they can go on vacation more, so they get more sun. So it's a false correlation. But putting all that to the side, it's provocative and it's a, it's a, an encouragement for people to, I would just say to consider the trade offs. Where you come down on that trade off, you know, is a personal decision that everybody

• 55:19Speaker 00

  has to make on their own, but it is thought provoking. I confess, there's a moment in your book, some really wonderful, personal, it's not a large part of the book, but there's some nice stories in the book of your own experiences and doing the research and where you went and your attempts to get sunlight to help you sleep better. We're not going to get into that, but it's really, there's some lovely writing there. But there's one moment, and it's such a small thing, but I just want to mention it. It's not scientific. This is not a scientific point I'm about to make, but I can put a gloss of science over it. I'm going to do that and let you comment.

• 56:02Speaker 00

  It's been a long, cold winter and there comes a moment in springtime when you're in the sunshine and you can feel the heat of the sun the way you can a fire in your fireplace. All of a sudden, the sun, which has merely been a pallid light in the sky through December, January, February, so in March, all of a sudden, you feel its warmth. And I think that you talk about in the, in your book that you feel like it's getting into your bones and you suggest actually there's now some evidence that it does get into your bones. And the idea...

• 56:42Speaker 00

  That we evolved on a planet with a big ball 93 million miles away that sends photons our way constantly. It would be weird if it was a killer. Now, you have to temper that because it is a killer up to a point. But that it wouldn't have health benefits would be weird. That you would have to constantly, especially when we were hunter gatherers, you'd have to be constantly being in the shade of the trees to make sure. Well, you're in the savanna where there's not much shade of the trees. Anyway, the whole idea of it is it's comforting. I'll just say it that way. It's not science.

• 57:25Speaker 00

  It's comforting to think that the sun is something of a friend. And through most of human civilization, I mean, we've worshipped it. I think that was a mistake. It's not a god, but it is a pretty extraordinary thing. And so I like the idea, that's all I'm going to say, that sunlight, especially on that first April or whatever month it is, when you actually feel the sun on your face and it lifts your spirits. It's a very human thing.

• 57:57Speaker 01

  Yeah, I'm so glad you brought that up because

• 58:02Speaker 01

  learning more about the science behind this and becoming more comfortable with the sun, it really, it improves your life on a daily basis. You realize that you had that fear in the back of your mind that was probably unnecessary. And so just like with anything else where you thought you had to fear something and you suddenly realize that maybe your fears were a little overblown. Like, that improves your life. And the evolutionary part of this, I think, is actually really important because as you correctly point out, a lot of the information we have about what look like to be these benefits of sunlight are coming from observational studies. And yes, the scientists do try to control for all the usual confounders,

• 58:45Speaker 01

  but that's, you know, that is a dark art.

• 58:51Speaker 00

  Dark art, well said.

• 58:53Speaker 01

  But so all we can do is go, well, that's interesting. And we're not going to get great. Randomized clinical trials where half the people expose themselves to a lot of sunshine and half don't because it would be unethical since we think they might be raising their risk of skin cancer. No funding agency is ever going to approve those studies. So it's just, you know, it's food for thought. But what's interesting here is we don't, we also, like, the reasons that we believe that skin cancer, that sunlight causes skin cancer are also from observational studies.

• 59:33Speaker 01

  We're not doing long-term clinical trials where we tell half the people to go out and fry themselves and, you know, we see if they get skin cancer. So it's all kind of guesswork. And anytime you're in that kind of situation, you kind of then want to default to evolutionary norms and ask, well, you know, what's, what do we have a pretty good track record of doing? And what's the weird intervention that's new? And so in this case, human beings spent their first hundreds of thousands of years getting 12 hours of sunlight a day.

• 1:00:16Speaker 01

  No other species that's out there seems to be suffering from, you know, too much sunlight. Like, it seems to be just us that are having this issue. So what changed? Well, we sort of switched to indoor life mostly in the past 100 years. And that's the weird thing that we need to start, you know, being skeptical about. Like, did something happen in that switch to indoor life that messed things up?

• 1:00:42Speaker 00

  Yeah, I don't, um, we are, as you point out, you do discuss evolution and our, and our origins in the first part of the book. We are relatively hairless. We're hairy, but we're not furry. And that's an interesting thing in and of itself. That would seem to be a bad strategy if sun was bad for you. Of course, there may have been some counterbalancing benefits for...

• 1:01:18Speaker 00

  Leaving survivors in the gene pool and so on. So it's all complicated. But you you close your book with some simple advice for adults and children. You want to share that? And listeners, take this with a grain of salt. And I encourage you to read Ruin's book. And if I were younger, and maybe if I were a parent worried about my children's exposure to sun, I might go investigate some of the observational and non observational studies to try to get a feel for how reliable they might be. Maybe you've exaggerated them. Maybe you've you've you failed to to add enough caveats. But what you got?

• 1:02:00Speaker 01

  Yeah, and I would I would I totally agree. Like, take it all with a grain of salt. I'm not certainly not a doctor either. And people shouldn't be forming their their medical opinions just from my book. But I do hope people start looking into it because of my book. And we're now in this kind of amazing era where we have these incredibly powerful research assistants on hand all the time. You know, the L L Ms that have read everything. And it is pretty amazing. If you ask them, you know, show me the studies on on X or Y, they'll pull them up. And you don't want to trust the, you know, the A I.

• 1:02:45Speaker 01

  Because it can sort of get the conclusions wrong sometimes. But it'll point you toward the sources and then go to the direct sources. And they can't be hidden. It finds them all. So it's actually a bit better than it's ever been. It to to like, look around and find what the foundational research is on these topics. So that's really worth doing. But in terms of what I think can be, you know, actionable advice for people. It's

• 1:03:17Speaker 01

  Go, you know, err on the side of moderation all the way, but don't get zero sun exposure. It's very clear from, you know, no matter how we look at it, that zero sun exposure is not healthy for people. It's also clear, and every scientist I've spoken with agrees, that burning is bad. If you're actually getting a sunburn, it means you have fried those cells beyond the point that they can recover. So they're basically all just committing suicide and taking themselves out of the game so they won't turn into cancer. But they don't even do that always successfully. So burns are truly, you know, a sign that you've gone too far. And I know from my personal experience that even when I'm trying not

• 1:04:01Speaker 01

  to burn, it can sneak up on you. So my own rule is to err well on, you know, the safe side of burning. To never get close to a burn. That said, I don't sweat the small stuff. It's kind of like, I'm kind of going back to what doctors told us to do in the 50s and 60s. Like, you know, don't get sunburned at the beach, don't get overexposed, but a little incidental sun exposure during your day is probably a very healthy thing. And that's, but it really, that's really going to be influenced by who you are, where you are, and especially your skin tone. People with darker skin tones can take a whole lot

• 1:04:43Speaker 01

  more sun exposure than people with light skin tones. And people with the lightest skin tones, who tend to have, often have red hair and reddish freckles, are the ones who are super susceptible to melanoma. So they are the ones who do truly need to really be careful. The recommendations are kind of written for them with the assumption that everybody else can just do the same thing and they won't be harmed by that. But now we're realizing that people with darker skin tones really shouldn't be doing the same thing as the people with very fair skin.

• 1:05:16Speaker 00

  My guest today has been Ron Jacobsen. His book is In Defense of Sunlight. Ron, thanks for being part of Econ Talk.

• 1:05:23Speaker 01

  Thanks, Russ. It was a pleasure.

• 1:05:31Speaker 00

  This is Econ Talk, part of the Library of Economics and Liberty. For more Econ Talk, go to EconTalk.org, where you can also comment on today's podcast and find links and readings related to today's conversation. The sound engineer for Econ Talk is Rich Goyette. I'm your host, Russ Roberts. Thanks for listening. Talk to you on Monday.