An argument for the sun

0:00Monday.com AI agents took over my work. And I absolutely love it. Chasing deadlines, writing status reports, updating stakeholders. Agents handle the daily grind now. I stay in the loop only when it matters. Create your own AI agent in minutes on Monday.com. Excuses are easy. An epic movie night? We don't have enough snacks. Dinner party with the girls? We'd have to decorate. Surprise date night? Nothing to wear. But Amazon's Prime same-day delivery lets you say yes before the moment slips away. Try that new popcorn maker, order those cheeky drink glasses, get that new perfume, and turn that I wish we could into an I'm so glad we did.

0:42Visit Amazon.com slash Prime to find millions of items delivered fast. Same-day delivery. It's on Prime. Available in select areas. Terms apply.

0:55All right. Sally. No. Helm. No. Co-host of Unexplainable. What do you got today? What are you working on? Okay, well, first I want to ask you a question. When you think of the sun, what do you feel? I immediately go to Teletubbies. Is that weird? That's not what I expected. You know, the baby sun that, like, wakes up in the morning and it's, like, really creepy. Okay, so I feel good. Warm. Totally. Classic effect of the sun. Makes me happy. Yeah. The sun is good. This feels like a simple question. Well, okay. I'm going to just let you know that I read a whole book about sun and it's facts on our bodies.

1:34And I learned from reading this book that the sun has just like all of these mysterious effects on our body. And there's a lot that we still don't understand. I mean, if you think about it, it's more bizarre than we give it credit for. It's like photons of light hitting us and ricocheting around. Photons of light from 93 million miles away. Yeah. That somehow make us happy when we go outside. Among many other things. So I really, I wanted to get into all this with the author of that book, In Defense of Sunlight. His name is Rowan Jacobson. And I have that interview for us today. Amazing. Are you going to explain the sun?

2:11I'm going to explain the sun totally and completely, and you'll never have any questions about it again. Okay. I want to, can I hear it? You can. Now? Now. Now?

2:37Rowan Jacobson, welcome to the show.

2:39Rowan Jacobsen:Thanks, Sally. Good to be here. All right, we're going to go deep down the rabbit hole together here. I want to first, though, can you just give me a little bit of a hint of the ending here? Tell me, after doing all this research, how have you changed the way that you relate to the sun? I think totally differently about sunlight and about light in general. People don't realize all the light that surrounds us is actually being absorbed by our molecules. So I started seeing light as this, you know, physical force that's interacting with my body in a lot of different ways. And like, what does that mean?

3:14Is it good? Is it bad? Is it both? But then if you want to get really cosmic for a moment here. I do, please.

3:21Rowan Jacobsen:Well, so all of the energy in our bodies was once light. All of that energy was sunlight. Came from the sun, came to earth, usually got absorbed by a plant and then made its way to us. So it's just sunlight taking different forms. And our entire consciousness is basically this flow of light transformed into different types of energy that is just moving through our bodies all the time. Over the past few decades, we've all been kind of trained to feel a little guilty when sunlight hits us. And that went away for me once I'd done this research. And it fixed my relationship with the sun, in a sense, you know?

4:02Yeah, let's talk about the history of that a little bit, because you're right. I think a lot of us feel guilty about the sun because of skin damage, which we will get into. But you do, in your book, you take us back to a time when heliotherapy was actually all the rage. So tell us about that. Like, starting in the 1800s, peaking in the 1920s, what did that look like? We are in a bit of a historical anomaly with this idea that sunlight is bad for us. That would have been a strange notion to most peoples throughout history. but especially this era, the heliotherapy era, which started in the early 1900s in both Europe and the US, and was really a reaction to two diseases that were rampant, tuberculosis and rickets.

4:44Rowan Jacobsen:And both those diseases can be treated with sunlight. Rickets is a lack of vitamin D, and vitamin D is produced in the skin with the help of sunlight. And one of the things that vitamin D does is it helps to get calcium into your bones. So your bones get hard. Kids in the industrial revolution who were never seeing the sun had almost no vitamin D in their bodies and they were all getting rickets. So they had soft bones. It's really bad disease. Even bigger was tuberculosis, which, you know, back in the 1800s was responsible for like one out of every four deaths in Europe and parts of the U.S. And it can be a pulmonary kind that infects your lungs.

5:26Rowan Jacobsen:And that's kind of like the classic consumption that we think of as, you know, like John Keats dying of consumption. But it can also infect the skin. It's like this flesh eating bacteria, basically. But that one can be fixed by sunlight. Once scientists figured out that both rickets and tuberculosis could be solved by light. They didn't quite understand why at the time, but they're kind of like, maybe light's good for other stuff too. And it actually, it got a little out of hand where they started believing that light was probably good for everything. So, you know, we're familiar with this whole sanitarium era where people would go up to the sanitariums in the Alps to take the fresh air.

6:07Totally. I've heard of people going to the Southwest. I do feel like I have a sense that back in the olden days, they were just getting sent off to take the outdoor cure kind of thing.

6:16Rowan Jacobsen:Exactly, the outdoor cure. First it was the Alps, and then California was advertising itself as early as like 1870 as the sanitarium to the world, right? Like, come to California. Yeah. Cure all your ills. Totally, I believe it. Well, that's the question. Like, did it help? Maybe it did help in some ways. Like, they were definitely kooks at a certain level. What did that look like? What were some of the kooky things they did? The kooky thing was they went too far. So they would purposefully get sunburns. Companies like General Electric made these UV lamps. You could get sunburned in the comfort of your own home.

6:50Rowan Jacobsen:And everyone bought these lights. They would hang them over their kids' cribs, right, for health. Oh, no. So irradiating children as they slept. So it was truly, truly kooky. I mean, were they onto something in that early era? It sounds like there is some truth to the idea that it helped with rickets, certainly, and possibly tuberculosis, too. Like, were they right? Were they wrong? A mix? The doctors who are running these heliotherapy clinics up in the Alps, they were noticing that all these patients, not only did their tuberculosis go away, but they just got healthier in general. They seemed more robust.

7:25Rowan Jacobsen:They had more energy. And we now know the reasons behind a lot of those factors, like a moderate dose of sunlight will reduce inflammation throughout the body. It'll lower your blood pressure. It'll generally improve your metabolism. So there's these sort of like low level general effects on the body that are positive in almost every way. But that only requires a moderate amount of light. So they were going too far. When doctors started realizing, wait a minute, we actually think that ultraviolet light might be a cause of skin cancer. the pendulum swung hard in the other direction. The messaging sort of got stronger and stronger and stronger after World War II, like stop frying yourself, you know, in the sun.

8:10Fair enough. Yeah. It does sound though like part of what was going on might be that they didn't know that UV light would cause skin cancer, which of course is something that we now think about, you know, it's very top of mind when we think about the sun. Tell me, how did that discovery unfold and how did it change the way that people relate to the sun? The researchers just started to realize it in the 1930s, kind of in the same era. And that was, I think, part of the issue is the exact same era that people were like, let's lie on the sun for 10 hours for our health. They were doing tests with UV and mice and realizing that ultraviolet light was looking like one of the major, if not the major cause of skin cancer.

8:54and suddenly worrying that all these people were getting way too much exposure in their lives. I mean, doctors start to realize that sun is affecting people's risk of skin cancer. Then they see the rates go up. I assume this must be the time when the public messaging that I'm really familiar with is born, when dermatologists do start to get the word out that we should protect ourselves from the sun. But tell me about that. How does that message get shaped and how does it take hold?

9:22Rowan Jacobsen:Really, like 1980 is the sort of pivot point. And before that, the sunscreens that were out on the market were really not there to protect you from skin cancer. They were there to help you get a great tan, right? They weren't even called sunscreens. They were called, you know, suntan lotions. That was the focus in the 60s and 70s is sunscreen that blocked UVB, the rays that caused burning, so that you could stay out in the sun longer to get more tan, right? It did not block UVA, which at the time they didn't think was a cause of skin cancer, but it would make you nice and tan. So then skin cancer rates are still going through the roof, especially in Australia, which is one of the sunniest places on Earth.

10:06Rowan Jacobsen:So 1980, Australia starts its Slip Slop Slap campaign, which with Sid the Seagull doing the public messaging. Slip, Slop, Slap. Slop, Slap. Slip on a shirt, slop on tongue, screen a slap on a hat. Okay, I love it. I love Sid the Seagull. I'm obsessed with him. I mean, does this work? Do people slip, slap, slap, and problem solved? It was super successful. So then that pretty much got copied around the world, variations on that. And sunscreens also changed. So the broad spectrum sunscreens hit in the 1990s mostly that blocked both UVB and UVA, and those are much more successful. And it does feel like somewhere along that trajectory, the tide really did change.

10:52And we did land in a place where the message that sun can be dangerous got out there. I think it's really, really out there. Oh, yeah. But as that was happening, there was some other stuff happening too. Some other corners of science where the benefits of sunlight were becoming clearer and clearer. So let's dive into that a bit. And I want to start with a scientist that you talk about in your book, Pele Lindqvist. He is an obstetrician in Sweden, and it's back in the 2000s. He's investigating a strange pattern that he had noticed among his patients. So tell me about that. What did he find?

11:24Rowan Jacobsen:Yeah, Pelle Lindqvist is an obstetrician in Sweden, and one of his specialties is blood clots. And blood clots tend to be more common in women when they're pregnant and right after they've given birth. He had noticed that less inflammation meant less blood clots, and he had a hunch that that was because of vitamin D. And he found this great data set called the Melanoma in Southern Sweden Study, which had tracked like 40 ,000 Swedish women for like 20 years. It tracked all their health metrics, including how much sunlight they got because the focus was melanoma. So they were trying to figure out what raised your risk of melanoma.

12:01So they tracked all of their sun-seeking behaviors,

12:04Rowan Jacobsen:I think is what they called it. Okay, that sounds perfect. What did they find? So we looked at the data and it turned out it was true. Like the women who spent the most time in the sunlight had higher vitamin D, lower risk of inflammation, and fewer blood clots. Wow. More sunlight, fewer blood clots. More sunlight, fewer blood clots. So then he started looking at other factors. And it turned out it wasn't vitamin D. Like the connection with actual sun exposure was stronger than the connection with the vitamin D levels. Okay. So there's something going on that's not just vitamin D, something mysterious in the sunlight.

12:41Right.

12:41Rowan Jacobsen:And he had no idea what it was, but he noticed it for blood clots, then he noticed it for diabetes. And so then he looked at the same data set just for all cause mortality. And the sun seekers had significantly less mortality than the sun avoiders. The sun avoiders were twice as likely to die from any cause as the sun seekers. So he published a study, and there's sort of like a notorious line in there now where he says, sun avoidance seems to be a risk factor for mortality a par with smoking, which upset everybody. But he wasn't even looking to make a statement. He was just like laying out the data.

13:20Why did it upset people? Well, the implication that avoiding the sun was like as bad as smoking for your health was not the message that, you know, powers that be had been like pushing for several decades at that time. And to this day, the official, you know, the official advice is do not ever expose yourself to sunlight without protection. So sunscreen or clothing, the proper amount of sun exposure of UV in particular to get is zero, right? So this was one of the first papers that really sort of flew in the face of that recommendation? Yeah. So it sounds like we're kind of tracing some swings here.

14:04We had the heliotherapy era where everyone started to feel like as much sun as possible is good. Then we swung in another direction where the public health message became largely the sun's dangerous, stay out of it, make sure you protect yourself from it. And now there's like some cracks in that. And some people beginning to suggest that maybe there's a middle ground, something sort of more in a gray area in terms of whether the sun is good or bad for us. What hints do we have that there are benefits of the sun that we didn't really understand, that science hadn't explained?

14:40Rowan Jacobsen:So that was sort of the next stage in this story. There had been a guy named Robert Furchgott. He was working with rabbit aortas because, you know, why wouldn't he? He just had some? He happened to have some in his lab? He was trying to figure out what, yeah, like what made blood vessels contract and dilate. Okay, fair enough. He had a jar of rabbit aortas on the windowsill in his lab, and it had been a cloudy day. And then suddenly the clouds cleared and the sunlight hit the jar with the rabbit aortas in it and the blood vessels dilated. And he thought, what the heck? And then some clouds came and they contracted.

15:20Rowan Jacobsen:and he called the effect photorelaxation. There were a lot of nitric oxide researchers out there trying to figure out how it worked because it seems like if you could master that, you could like really improve cardiovascular health. Nitric oxide. Okay, what is that? What does that mean? Nitric oxide is a very simple compound. It's just a nitrogen and an oxygen put together, but it dilates blood vessels. It tells the muscle and the blood vessel to relax. Which, I mean, that's good, right? That lowers blood pressure. It lowers blood pressure, which is, and cardiovascular disease, number one cause of death in the world by far.

16:00It's the biggie. So anything that lowers cardiovascular disease is a huge win for public health. Like what hints do we have that there are benefits of the sun that we didn't really understand, that science hadn't explained?

16:14Rowan Jacobsen:So that was sort of the next stage in this story. It's after Pelle Lindquist's papers, a dermatologist in Scotland named Richard Weller and some other colleagues of his discovered was that the skin actually produces a bunch of nitric oxide when hit by sunlight. The more sunlight that hits your skin, the more nitric oxide will be released into your bloodstream, the more blood pressure goes down. Wow. So he's discovered a way that standing in the sun can improve your heart health, which again, it's kind of a surprising finding to me, the idea that light is doing all that. And I mean, this has huge implications, right?

16:58What are the implications of that for our health? Huge, because as we were talking about, cardiovascular disease is the number one killer. So if you could reduce blood pressure even modestly, you could save millions of lives.

17:15Rowan Jacobsen:And skin cancer, and this is surprising to a lot of people, it doesn't kill very many people. It's not a big killer. It's not one of like the top 40 causes of death. Cardiovascular is number one. If you took that research seriously, then you had to sort of ask the question of trade-offs. Like, yes, sunlight raises your risk of skin cancer, but if it lowers your risk of heart disease, then how do we pick, right? So we've now talked about ways that sunlight can affect your heart health. We've seen some evidence that it might affect all-cause mortality, so it might just make you healthier in general.

17:52But we still haven't really talked about the theory that I would have had coming into this conversation about what sunlight is doing for you that's good, which is vitamin D, which I've heard so much about vitamin D, the sunshine vitamin. Being in the sun gives you vitamin D. I've seen and taken vitamin D supplements, which I did learn is not actually a vitamin. What is it? It's not a vitamin. It got misnamed back when they discovered it in the 20s. It's a hormone. And it's used in tons of different ways by the body. We used to, 20 years ago, think it was like the magic bullet that was like the wonder drug that could cure everything or could at least prevent disease across the board.

18:34Rowan Jacobsen:And that was because when we looked at levels of vitamin D in people's blood, the ones who are deficient in vitamin D had higher levels of every disease you can think of. Cancers, heart disease, autoimmune diseases, depression, diabetes, dementia, you name it. Raise vitamin D and you should have lower levels of all those things. The easiest way to do that would be to tell people to go out in the sun, but we didn't want to do that because we didn't want to raise people's risk of skin cancer. So instead, the advice was stay out of the sun, but take vitamin D supplements. But there's been huge clinical trials to prove that worked.

19:15Rowan Jacobsen:And they have across the board failed to show that these vitamin D supplements fix any condition whatsoever. Wow. What did science feel when those results came out? It sounds like a real upending of the conventional wisdom. It was, except it turns out conventional wisdom is really hard to upend. You can upend in practice, or in theory, but in practice it's really hard. But that was another big mystery. Like, how could that be? If people with naturally high levels of D have lower rates of all these diseases, then how come raising that D artificially with pills makes no difference? And how come?

19:54What do you think?

19:55Rowan Jacobsen:Any guesses? I mean, my guess is that it has to do with sunlight. Oh, you knew. So D was just a marker for sun exposure. And D is a really, really accurate marker for sun exposure. You get more sun, you're going to have higher levels of D. So that D readout in people was really just saying, these people with lower diseases are getting more sunlight. So probably D is part of the reason for the beneficial properties of sunlight, but it seems like it's got to happen through your skin for some reason. There's something different when you're taking it orally. We tend to do this where we learn a little bit about something and we boil it down to one very simple formula, like, oh, So D good, take D pill, you'll be good.

20:44And then we get surprised when it turns out the body works in incredibly more complicated ways than that. So this seems to be one of those cases. What do we still not know about how sun is affecting our bodies? What are the big mysteries that remain?