[00:00:00.030] - Dr Lemanne

What do you think the annual deaths from adequate exposure to outdoor sunlight is in just the United States? You have found your way to the Lemanne-Gordon podcast where docs talk shop. Happy eavesdropping. I'm Dr. Dawn Lemanne. I treat cancer patients.

[00:00:20.530] - Dr Gordon

I'm Dr. Deborah Gordon. I work with aging patients.

[00:00:24.230] - Dr Lemanne

We've been in practice a long time.

[00:00:26.210] - Dr Gordon

A very long time.

[00:00:27.750] - Dr Lemanne

We learn so much talking to each other.

[00:00:29.820] - Dr Gordon

We do. What if we let people listen in? Today's episode, Dr. Lemanne and I look into how light shapes human health, and we go way beyond vitamin D. We explore why even a gray day outdoors can expose you to dramatically more illuminance than ordinary indoor light, and what that might mean for circadian rhythms, mood, and overall physiology. We also wrestle with provocative but debated research on sun avoidance and all-cause mortality, including where those arguments may be compelling and where the evidence is still mixed. Along the way, we take on three especially surprising ideas: that cloudy outdoor light can still vastly exceed indoor light levels, that chronic sun avoidance may carry risks beyond what most people think of, and that different wavelengths of light, including near-infrared light, may affect nitric oxide, blood flow, mitochondria, and brain function. Throughout, we keep one foot in the clinic and one in the literature. This is not a lecture, and you should not base anything you do for your health on what we say here. Always check things out with your own provider first. But we hope you'll enjoy this for what it is, an unscripted but grounded unedited conversation between two physicians thinking out loud, learning together about light and health with key studies and probably way too many references collected for you in the show notes.

[00:02:06.050] - Dr Gordon

And today, a special surprise is hidden at the very end after all the credits for our most persistent listeners.

[00:02:15.140] - Dr Lemanne

So, Deborah, before you got here, I took some measurements of Light.

[00:02:20.160] - Dr Gordon

Oh, I was hoping you were gonna do that for my number one question.

[00:02:24.250] - Dr Lemanne

I have a light meter that measures lux, L-U-X, the unit of light photons, and it's on my iPhone. It's an app.

[00:02:32.370] - Dr Gordon

Before we really get rolling, we should clean up one definition.

[00:02:36.790] - Dr Lemanne

Yes, I said my light meter measures lux, the unit of light photons. More simply and accurately, lux means how much visible light falls on a surface. It's lumens per square meter.

[00:02:50.440] - Dr Gordon

So your app is really telling us our world experience, how much light is landing here in the room or out in the yard.

[00:02:58.020] - Dr Lemanne

Exactly. And it's not an engineering-grade device or anything like that, but it does give me an idea. And I brought it because I wanted to— can I give you a little quiz? You can say no.

[00:03:09.900] - Dr Gordon

Oh dear, you can give it to me, but I think it's probably going to be asking me the questions that I wanted to ask you as soon as we got here today. Go ahead.

[00:03:17.590] - Dr Lemanne

Okay, I won't kooz you, but I'll tell you that I measured the light in the room that you're sitting in right now, and I measured it with the shades open. Tom suggested that. And with the shades shut. That was my idea. And with the shades shut, I got 245 lux. L-U-X.

[00:03:37.470] - Dr Gordon

And so everybody knows, this is a small room near an open backyard, and there really weren't very many windows to uncover. But anyway.

[00:03:47.890] - Dr Lemanne

But you have one light bulb above you and both the windows were shut at that point, the way they are now.

[00:03:51.990] - Dr Gordon

But the light bulb was on.

[00:03:53.100] - Dr Lemanne

The light bulb was on. Yes, just like, just exactly the way you are now. And then see those, see the windows to your right and then behind your head?

[00:03:58.880] - Dr Gordon

Yes.

[00:03:59.220] - Dr Lemanne

So I opened those shades and we got the light up to 430 lux, twice as much.

[00:04:05.610] - Dr Gordon

That is great.

[00:04:08.320] - Dr Lemanne

And I measured outdoors.

[00:04:09.620] - Dr Gordon

That's what I wanted you to do.

[00:04:12.010] - Dr Lemanne

Oh, I'm changing my mind. I'm gonna ask you, how much stronger do you think the light was outdoors? So we have 205 in a room with the light bulb on but the curtains shut, and 430 with the light bulb on and the curtains or shades open. So if I went outside in the backyard there, and it's cloudy day.

[00:04:31.650] - Dr Gordon

Yes, which—

[00:04:32.290] - Dr Lemanne

Yeah, there was no bright sun or anything like that. It's gray.

[00:04:35.510] - Dr Gordon

Oh.

[00:04:35.820] - Dr Lemanne

It drizzled last night. There weren't any blue spots in the sky. But how much do you think the—

[00:04:41.550] - Dr Gordon

I am fairly certain it's in the multiple thousands, meaning a multiple of 5 to get up to 2,000, maybe 2,000 to 3,000, 4,000 on a shady day. But I could be decimals off.

[00:04:57.770] - Dr Lemanne

So compared to 245, which is what you're sitting in now, outdoors it was 64,160.

[00:05:05.630] - Dr Gordon

I was only off by 60,000. Before we go on, may I ask you a quick favor? Or hit the subscribe button. Your hitting that subscribe button really matters. You're making sure cutting-edge ideas that matter to you move to the center of medical discourse where they belong. Thank you.

[00:05:23.830] - Dr Lemanne

Thousands, thousands of times more bright. And when you go from indoors to outdoors, you don't feel like there's that much difference.

[00:05:32.750] - Dr Gordon

You don't, not on days like this. I'm thinking, oh, I wish I could get a little actual sunlight on my face. My body, face, head, eyes, whatever, but I'm getting it on a day like today.

[00:05:43.570] - Dr Lemanne

You are, and the reason we don't perceive that the light is changing that much when we, thousands of times.

[00:05:49.670] - Dr Gordon

Tens of thousands.

[00:05:51.260] - Dr Lemanne

Yeah, tens of thousands of times we go outside is because our pupils contract so nicely and perfectly. So the amount of light going into our eyes stays in the same range because our pupil, you've got the door or the pupil open wide when you're in here and it shuts, just leaves a little crack, a little tiny pinpoint when you go outdoors. So our eyes adjust so that they keep about the same amount of light coming in no matter where you are, but the amount of light actually hitting your body is thousands of times greater if you just step outside, even on a cloudy day.

[00:06:23.290] - Dr Gordon

And if I were wearing— actually, I'm gonna ask— there's 17 questions I wanna ask you about that, but the first one I'll ask you is if the clouds parted and the sun came out, how much more than 64,000 lux would you be?

[00:06:37.590] - Dr Lemanne

I have done that. It's up to 100,000.

[00:06:39.750] - Dr Gordon

So it's not that much more. Multiplicity is greater going from indoors to outdoors than from cloudy to sunny.

[00:06:47.430] - Dr Lemanne

Absolutely. Isn't that interesting? Yeah, that's a good point. Thank you for making me think about that. Yeah.

[00:06:53.560] - Dr Gordon

So because of the— both the hazards long overplayed by some of our favorite dermatologists and the benefits recently more celebrated have been more that we've missed the value of cloudy days, I think, in our— to the degree that we appreciate the sun, I've been overlooking the little benefit I got from my little 10-minute walk today in the cloudy day.

[00:07:20.990] - Dr Lemanne

There's a lot of benefit from sunbathing. And in fact, I think that's another statistic that was really surprising. So I looked up how many people get killed in, Globally in wars every year. It's horrible. And I'm talking about fighters.

[00:07:36.820] - Dr Gordon

I don't mean to laugh.

[00:07:37.930] - Dr Lemanne

No, I understand, but just the idea of doing that.

[00:07:40.500] - Dr Gordon

Wasn't really our topic for today, but you go with it.

[00:07:43.790] - Dr Lemanne

Okay. So according to the UN statistics, global military action deaths, that means people getting blown up with bombs and bullets and things like that. Now we're not talking about the downstream effects of infrastructure destruction, but civilians and fighters. Killed annually. In 2022, which is a pretty bad year, there were about 230,000 such deaths all around the world. And there was a huge war in Ethiopia that killed 100,000 people in itself. And then the war in Ukraine started, the war between Ukraine and Russia. And then in 2020, so 230,000. In 2023, the war in Ethiopia apparently sputtered and shut down, but the war in Russia and Ukraine kept going. And then there was the war between Israel and Gaza got going. And so in that year, 2023, which is the last year that we have good statistics for so far, they're still busy counting, I think, those were 250,000. So that's the annual deaths from war.

[00:08:44.350] - Dr Gordon

Okay. Quite significant. Yeah. Considering we're not in a world war.

[00:08:48.530] - Dr Lemanne

Exactly.

[00:08:48.930] - Dr Gordon

Theoretically right now.

[00:08:50.850] - Dr Lemanne

Exactly. And what do you think the annual deaths from adequate exposure to outdoor sunlight is in just the United States?

[00:09:00.390] - Dr Gordon

Well, so—

[00:09:01.310] - Dr Lemanne

I'll tell you.

[00:09:02.010] - Dr Gordon

Yeah, but I bet it even— I don't think they could calculate it without underestimating it because we're learning so much more about that.

[00:09:08.860] - Dr Lemanne

This underestimate then is 340,000. And that's just in the United States. 408,000 in Europe. They're worse off. And if you take— and that's pushing up against a million people. And if you extrapolate that to the rest of the world, it's probably well over a million people a year die from not going outdoors or from wearing sunscreen when they do go outdoors. And those aren't invented numbers. The U.S. figure comes from Holm and colleagues published in 2016 in the journal Dermato Endocrinology. The European figure is from Lindqvist and colleagues, also in 2016, in the Journal of Internal Medicine. And both looked at all-cause mortality in sun avoiders versus regular sun exposure groups.

[00:09:54.140] - Dr Gordon

Dawn, can we pause for a minute on how people should hear these numbers?

[00:09:58.400] - Dr Lemanne

Yes, when we talk about deaths linked to sun avoidance, we're drawing on real studies, but those are estimates and they're not the last word and they should be taken in context.

[00:10:08.440] - Dr Gordon

So some of what we're talking about today comes from strong clinical studies or large population data, and some comes from observational or emerging research that is more suggestive than definitive.

[00:10:23.090] - Dr Lemanne

And in a conversation like this, we're thinking out loud as practicing physicians while trying to stay anchored to the literature.

[00:10:28.800] - Dr Gordon

So if we occasionally sound more certain than a printed review article would, please hear that as conversation, not as a claim that every point is fully settled science.

[00:10:39.440] - Dr Lemanne

And if you want to see the papers behind the major points, we've listed them in the show notes.

[00:10:44.820] - Dr Gordon

Or from wearing sunscreen.

[00:10:47.130] - Dr Lemanne

Yes.

[00:10:47.790] - Dr Gordon

Could we put that in flashing neon lights? And where that is— it can be overused to deathly effects.

[00:10:55.230] - Dr Lemanne

And I want to talk about that because people worry about dying from skin cancer. And melanoma is the skin cancer that people can die of if they are unlucky enough to get a type of skin cancer. But the basal cell and the squamous cell carcinomas are rarely fatal. But melanoma can be fatal. And the annual deaths in the United States from melanoma are 8,400.

[00:11:22.430] - Dr Gordon

Actually, that surprised me. That's— that seems higher than I would have thought.

[00:11:26.430] - Dr Lemanne

Compared to things like breast cancer, which are approaching 70,000 a year, it's not insignificant and not— even one death is not of no significance. It's very significant. And the scale is so different. So millions of people dying in the— over the— 340 deaths per year in the United States, millions around the world perhaps. Or a million or more around the world, and compared to 8,400 from sunlight. So many more deaths from lack of sunlight than from sunlight itself. And another thing that I am really interested in is, are there cancers that are specifically associated with lack of sunlight? And I looked that up and there are. So I'm going to list them.

[00:12:14.150] - Dr Gordon

Okay.

[00:12:14.860] - Dr Lemanne

You're gonna have heard of these conditions: colorectal cancer, lymphoma, both Hodgkin and non-Hodgkin, prostate cancer, breast cancer, bladder, kidney, ovarian, pancreatic cancer. Very much associated, perhaps, we think, we're starting to see, with an indoor lifestyle. And this is not because of lack of exercise. People who go outdoors typically are going outdoors to get some exercise. It seems to be the lack of light.

[00:12:43.090] - Dr Gordon

The lack of light.

[00:12:44.540] - Dr Lemanne

Sunlight.

[00:12:45.420] - Dr Gordon

Sunlight, right.

[00:12:46.220] - Dr Lemanne

Or enough light. So you can't get the kind of light you get outdoors. We just showed that with the lux meter. 60,000, almost 65,000 lux compared to 200 to 400 and something indoors with a light bulb.

[00:13:00.240] - Dr Gordon

Speaking of light, though, this is standard lighting in here. What if I were somebody who bought a Sunlight box, and those are used commonly to relieve— I have one. I think I'm going to get one next year for the winter.

[00:13:17.140] - Dr Lemanne

Mine puts out 10,000 lux.

[00:13:20.670] - Dr Gordon

That was the question I was going to ask.

[00:13:22.430] - Dr Lemanne

So that's not anywhere near the 64,000 on a cloudy day and the 100,000 on a bright day outdoors.

[00:13:31.320] - Dr Gordon

So this sun and Cancer effect has to be a little indirect. I don't know how many people who've had 1 or 2 or 3 melanomas. And by the way, there is something reported to reduce your risk of melanoma, but I'll get to that in a second, besides sun behavior. But a significant portion of my personal, albeit limited, acquaintance with melanoma is that they're not in sun, highly sun-exposed areas the way basal cell and squamous cell are.

[00:14:03.140] - Dr Lemanne

Exactly. The more sun-damaged the skin, the less likely that person is to die of melanoma. And we think that chronic exposure to the sun, like farmers, and they don't have as high a death from melanoma as people who get intermittent sunburns. So chronic sun exposure may be protective. And so that's really interesting too.

[00:14:27.580] - Dr Gordon

That is, and it makes me think— so one of my very close personal acquaintances, my She won't mind me saying this. This is not a HIPAA deviation. My wife is an athlete, and she's all her life been an athlete outside, but she comes from the Northwest. She comes from Tacoma. So she would get a lot of sun in the summer months and of course get sunburned. And in the winter months, there was not very much sun to be had, not enough, maybe enough to, excite your lux meter, but perhaps not enough to ward melanoma off from the— to still be insufficient to count as farmer's exposure to the skin. But so it's mediated by something other than skin damage, sun damage to the skin, and the sun is somehow protected, protective. Is there an understanding for the mechanism of, besides a genetic risk perhaps, of why Some people with intermittent sun— one kind of skin cancer and others get melanoma? Yes.

[00:15:35.660] - Dr Lemanne

We— so your wife survived.

[00:15:38.250] - Dr Gordon

Yes.

[00:15:38.460] - Dr Lemanne

So people who get melanoma who've had a lot of sun exposure do better if they get melanoma than people who have not had a lot of sun exposure and who get melanoma. So the— some of the theories that have been thrown around and tested to various degrees of confirmation are exposure during youth, extreme youth, childhood, thought in some cases to be more risky than exposure during adulthood. But it seems to be that, you know, certainly melanoma is caused by UV radiation in most cases, although not all cases. We have cases of melanoma in the eye or in the mouth or in the anus or other parts of the digestive tract.

[00:16:17.900] - Dr Gordon

Or on the sole of the foot. The sole of the foot. That was the most recent one I've heard of.

[00:16:21.150] - Dr Lemanne

Yes, and in the nail beds and things like that. That's where people who are not going to get melanoma due to UV will get melanoma. For instance, Africans. So Africans don't get melanoma in general on their legs or back or face. They do get it in the— on the soles and on the— in the fingernail bed. And so we think that those are not necessarily related to sunburn history at all. But yeah, there is some evidence that sun exposure itself chronic and frequent sun exposure decreases the risk of both getting melanoma, although it doesn't remove it completely. You can still get melanoma, your risk is just lower. And if you do get melanoma, previous sun history and skin damage actually improves your chances of survival.

[00:17:08.240] - Dr Gordon

So it's a little hard to get previous exposure once you're diagnosed with it.

[00:17:13.110] - Dr Lemanne

Yeah, you're kind of stuck with figuring out how to get rid of the melanoma once you've got it, yes.

[00:17:16.960] - Dr Gordon

Get rid of the melanoma and reduce its risk of recurrence. There are two separate things I want to raise here. One is whether probiotics affect melanoma outcomes, and the other is a specific supplement my genetics consultant flagged. Can we take probiotics first?

[00:17:35.030] - Dr Lemanne

The study done at MD Anderson looking at probiotics just off the shelf found an increased risk of melanoma death in patients taking the current treatment for melanoma, which is an immunotherapy. Those patients who took immunotherapy for melanoma along with off-the-shelf probiotics— oh, this sounds like a good idea, even fancy expensive ones— their death rate was higher. So you definitely want to do your homework if you have melanoma and find out what the current microbiome du jour is, as best we know, because that will change. And it's unlikely that there's one organism that's going to help with melanoma. There's probably Maybe it's probably, I'm gonna guess, but I'm not gonna prove this, but I'm gonna guess that it's probably that you're not doing something else. Maybe you're not taking the off-the-shelf product because you're taking this one that your doctor gave you.

[00:18:24.450] - Dr Gordon

And on the supplement question, the product my genetics consultant flagged is called Shade Factor by Life Extension. It's a botanical combo vitamin formulation. One of its two main ingredients is niacinamide, which I understand has published data for decreasing skin cancer recurrence. And particularly I'm talking for niacinamide about basal cell cancer and squamous cell cancer.

[00:18:54.130] - Dr Lemanne

I'm going to be really persnickety here. It's not recurrence. It's a new—

[00:18:59.120] - Dr Gordon

Good point.

[00:18:59.850] - Dr Lemanne

Yes.

[00:19:00.390] - Dr Gordon

Good point.

[00:19:00.790] - Dr Lemanne

So we're not protecting against— so this is really important. You can protect yourself against skin cancer if you've had skin cancers in the past. And this is published in the New England Journal in 2015. New England Journal of Medicine, the— a lot of doctors. And meaning it's treated as a very sacred document for good reason. You have to have done a very careful and high-quality study to get your study published in the New England Journal. So this study looked at— this was a randomized controlled trial with— so half the people got placebos and the other half got niacinamide. It's also called nicotinamide. It's a vitamin, it's B, it's related to niacin, but it's not niacin. And, but it's niacin and nicotinamide are both in the B3 vitamin family. In any case, all of the subjects, whether they were on placebo or the nicotinamide, had a history of actinic keratosis, other types of premalignant and malignant skin diseases. And over the course of the study for several years, if as they were taking 500 milligrams twice daily, their risk of a new tumor went way, way down. I think down to something like, down by 20% or something like that.

[00:20:13.360] - Dr Lemanne

And the placebo group had no such protection. And the protection went away when the study was done and they stopped taking this. So that was really important, but I wanna make sure that there's a, that we are very careful about the distinction between recurrence, which means the first tumor never was completely cured. It's still there somewhere in your body. Versus a new skin tumor which arose separately from the first one which had been cured.

[00:20:38.540] - Dr Gordon

A very good point. The second ingredient in Shade Factor is Polyplocotomus. It's a tropical fern extract, an oral pectin, if you will. My genetics analysis software flags it specifically for patients with elevated genetic risk for melanoma. But I'll be transparent. I hadn't confirmed the underlying citation before we sat down, so I'm putting that reference in the show notes once I've tracked it down.

[00:21:07.870] - Dr Lemanne

Looking into it right now, my sources say the proposed mechanisms for Polypodium leucotomos, boy, that's a mouthful, isn't it?

[00:21:15.500] - Dr Gordon

Yeah.

[00:21:16.210] - Dr Lemanne

Are related to its antioxidant actions, reducing UV-induced DNA damage, scavenging reactive oxygen species, and so on. It's been studied primarily as a photoprotectant, just so, this source agrees with you, whether it meaningfully reduces melanoma risk in genetically predisposed individuals specifically is what I'm reading here. That's a narrower claim. And I, so I guess we'd want to see some study results before we could say for sure that it's helpful.

[00:21:43.410] - Dr Gordon

I'd agree. I'll add this. My wife had 3 melanomas over the years. I started her on Shade Factor some time ago and she hasn't had one since. I know very well that's an N of 1, but you like those, Dawn.

[00:21:56.910] - Dr Lemanne

I do.

[00:21:57.530] - Dr Gordon

Even though they don't really prove anything, but it's why I keep the question open and I will consult my genetics authority and see if they have anything specific about melanoma and we'll put that in the notes.

[00:22:11.000] - Dr Lemanne

Because you and your wife, you're extremely proactive when it comes to health. So could it be one of the gazillion other things you've been, you've both been doing, like the food, the outdoor time, that has improved the general trajectory of her health? We'll follow up with that citation for our listeners.

[00:22:27.820] - Dr Gordon

The big elephant in the room about all this is, I— still, if you get a note from a dermatologist who's removed a basal cell or a squamous cell, and I don't get many from that have melanoma, but I'm sure it would say it in capital letters, they say absolutely avoid sun exposure without protective sunscreen.

[00:22:47.730] - Dr Lemanne

That is true if that's— if your goal, your entire health goal is to never get one of those types of little skin tag tumors again. However, you're increasing your risk of— one thing that's really, I think, people don't understand is high blood pressure. You're increasing your risk of death from cancer, cardiovascular disease, stroke, high blood pressure. All of those things are directly influenced by lack of sunlight, directly, and by use of sunscreen. I think you were gonna— I know that you've talked to me about nitric oxide. Nitric oxide production from sunlight and how that relaxes the blood vessels. So I know that's a point of interest for you.

[00:23:26.380] - Dr Gordon

It is a real point of interest, and it— I think it's remarkable how it's emerged in this whole conversation because we knew for a long time that latitude influenced your risk of multiple diseases and cardiovascular disease, others, but multiple sclerosis was the most notable one. Oh. And we all assumed for a long time it was vitamin D. But when they actually tried to say, "Is vitamin D the active ingredient in sunshine?" The only disease it reliably reproducibly reduced the risk of was osteoporosis. It really didn't have an effect, vitamin D without sunlight, in reducing the risk of multiple sclerosis or cardiovascular disease. And it, I think it's a brilliant leap of scientists' insight that they discovered it was nitric oxide.

[00:24:18.750] - Dr Lemanne

It's nitric oxide and it's probably a lot of other things too.

[00:24:21.990] - Dr Gordon

Probably that are even lesser obvious, but nitric oxide particularly is hard to imagine how they understood that mechanism because you can't— Dr. Lemanne, do you know your nitric oxide level in your blood?

[00:24:36.360] - Dr Lemanne

I think it's fluctuating by the second, and in each little endothelial cell, there's a different level depending on what's going on at that point. And that's one of the wonders of biology. Things are feedback levels at the tiniest levels, at the smallest levels and the deepest levels, are quite complex and things are changing momentarily. But the sunlight exposure, sunlight mortality, the mortality from lack of sunlight is not fixed by taking vitamin D pills.

[00:25:07.740] - Dr Gordon

It is not?

[00:25:08.310] - Dr Lemanne

No, it doesn't change it at all. And so the UK and Sweden have studies showing that link sun exposure with reduced all-cause cardiovascular and cancer mortality. You could have stopped with all-cause, but— and they specifically say through vitamin D independent pathways such as nitric oxide photomobilization. So what I understand is that thin tissue layers are extracted from some unfortunate beast and placed in some type of bath and probably on some type of surface in this bath such that we can shine ultraviolet light on them and watch nitric oxide bubbles bubble out of these tissues when we shine the light on them. So I'm— I think that's one of the ways that this kind of measurement is done and how this mechanism was discovered and studied. And no, you can't study that in a person. But let's take hypertension, high blood pressure. So lack of sunlight is known to be directly associated with high blood pressure. So if you're— for instance, if you have a history of one of these less dangerous skin cancers, squamous cell carcinoma, basal cell carcinoma, or the precancerous actes, and your doctor's burning them off, and you're not getting around to taking your nicotinamide 500 milligrams twice a day, and so you're getting more, you are still much more likely to die from lack of sunlight than you are to die from any type of skin sun-related disorder if you were to stop your skin protection.

[00:26:41.080] - Dr Lemanne

Again, a million people in the United States and Europe a year dying because they avoid the sun. And one of the major diseases caused by sun avoidance is high blood pressure, which is really amazingly common.

[00:26:53.320] - Dr Gordon

Very common. And there's a lot more than that. And getting into— interesting to get into the brain contributors of it, but you can just imagine the benefits with every organ in the body if you're improving circulation.

[00:27:07.590] - Dr Lemanne

There was a study in 2025 that looked at sunlight on the torso, the human torso. And it turns out this is not UV, but a certain wavelength of infrared light. When you're standing in the sun, goes straight through the torso and comes out the other side, even with your clothes on and everything. So you don't have to go out naked or anything like that. Just go outdoors in your clothes, goes right through you. And just shining that on the torso improved blood flow and vision to the eyes a few minutes later. And that was thought to be mediated by mitochondrial function improvement throughout the body. So the mitochondria in the torso where the light was, and the eyes were protected from this light, they were just, their torso was exposed. And the eyes, the mitochondria in the eyes received some message, a chemical message from the mitochondria in the exposed area in the torso saying, "Hey, things are good. Perk up. Work better." And so there's a distant effect from sunlight.

[00:28:06.220] - Dr Gordon

Ooh, as if the little mitochondria are talking to each other, saying, "We've got the goods, buddy. We've got the goods. Go for it." Yes, exactly.

[00:28:13.370] - Dr Lemanne

So sunlight, not only UV A and B—B is what makes vitamin D—but also these other wavelengths in the red part of the spectrum, which we can't see, go through the body, all the way through, and tune up the mitochondria. And it's much more effective to just go outdoors. People will sell you now a big red light box with an array of red light bulbs, and that's great, that's fine, but you can go outdoors and get twice the exposure than you would with your expensive light box.

[00:28:44.810] - Dr Gordon

And there are people who live in parts of the world where— I'm thinking of pictures from crowded urban settings. I remember during the COVID pandemic talking to somebody who lives in an apartment in the boulevards of New York City and suggesting, when we were getting some idea that sunlight was helping with immunity and response to COVID, they didn't have any place to go outside and get sunlight. And they said even if they were free to travel and go downstairs and walk up and down their streets in Manhattan, they were getting indirect sunlight if they could actually go outside, right? Because the sunlight that comes, it's not direct overhead if it's not leaving a shadow on the ground. If you're in the shadow of the building, you're still getting some sunlight because that's equivalent to going out on a cloudy day, probably. You could take your lux meter.

[00:29:40.470] - Dr Lemanne

I believe mine was free.

[00:29:41.930] - Dr Gordon

No, I think you're right. And I think I'd— Downloaded it some time ago at your inspiration.

[00:29:47.520] - Dr Lemanne

And so, yeah, the COVID era was an extraordinary time. And people who lived in cities who were forbidden from leaving their houses, that was a very tough, very difficult moment. But now one can go out. Yeah, getting to a park is important where you can actually have some real sunlight. And different people need different amounts. I think that's one of the interesting things about the latitude connection. Yes. There are people now— we've got a melting pot here in the United States. We have people from different skin darkness backgrounds all living together. And so have you heard of the Fitzpatrick skin types? No. So there's 6 of them. And they're fuzzy. Yeah. And here are the 6 Fitzpatrick skin types. Number 1, always burns and never tans. But then the subtext is that the time to burn if the UV index is 3 or 4 is 45 to 60 minutes. 6 to 7 is 5 to 30 minutes, et cetera. So it depends on how long you're out. So always burns, never tans. So very fair skin. Fitzpatrick 2, usually burns, tans minimally. And then they give the time, 50 to 70 minutes if there's a low UV index, up to a high UV index of 10 or more, which is, it's hard to get to except in the midsummer at solstice at noon, or sometimes if there's a big solar storm going on, 50 to 20 minutes.

[00:31:08.970] - Dr Lemanne

15 to 20 minutes. And then it goes all the way up to type 6, which is black skin, never burns, can be in the highest UV for more than 50 minutes. And then 5 is brown skin, very rarely burns, can be in the highest UV for 20 to 20, from 35 to 50 minutes. And then type 4 is rarely burns, tans easily. That's me. So I'm Fitzpatrick 4, I think. I've never had a dermatologist tell me. I'm gonna see a dermatologist next month. I'll ask them, say, "What's my skin type?" and see what they say. But this is pretty fuzzy. Yeah. Okay.

[00:31:41.820] - Dr Gordon

Anyway. You skipped my number, I'm sure. I'm very—

[00:31:44.390] - Dr Lemanne

There's 3, sometimes mild burn, and average tan. Yes. And you can stay out in low index of 3 and 4, which you can get from Siri if you ask Siri, "Hey Siri, what's the UV index?" Oh.

[00:31:58.190] - Dr Gordon

The UV index is currently 3. Thank you, Siri.

[00:32:01.660] - Dr Lemanne

So yeah, you could go outdoors right now, UV index of 3 or 4, for 70 to 90 minutes without burning, and you'd probably tan. And if you, I think, I know that you go outdoors all the time, every minute when you can. So you probably aren't gonna burn then. You probably have some protection in the form of tanning.

[00:32:19.370] - Dr Gordon

I do, although a lot of it has just turned into brown spots over the decades. That's my, when people ask you, is there anything you regret in your youth? I said, I wish I'd just used sunscreen. I never really used sunscreen growing up, but I wouldn't mind if I'd put it on my face. No, that's just vanity speaking, but There's a— one of the things I've noticed with age and these skin types, I wonder if they all kind of change. So speaking to Fitzpatrick number 4, are you— do you notice that you tan less easily than when you were younger?

[00:32:52.090] - Dr Lemanne

A little bit, but I will tan in 4 minutes. Oh. It's— you can watch it happen. And then it goes away when I go indoors in 4 minutes. Well, there's that. Do you remember this doll called Suzy Suntan? I don't. Oh. When I was a kid, for a moment, there was a doll called Suzy Suntan. You put her in the sun. And she turns brown, and you bring her in and she turns pink again. And I don't know if I actually had one, but I remember the ads and I remember seeing them in the toy store. But I'm like that. I don't start off pink, I start off beige, and then we'll get tan. So you can see the tan lines where the clothes are and everything in just a very few minutes, and then it goes away mostly, and I'll keep some of the tan. And I rarely get burned. I'll get burned if I go out at noon at altitude on solstice and stay out for 3 or 4 hours. I get a burn. But it's happened 3 times in my life. I don't even know what's wrong. I remember asking my mother once, "Why does my neck hurt?" And she said, "Oh, you're sunburned." This is a unique experience.

[00:33:50.840] - Dr Gordon

I don't know it. Yeah, yeah.

[00:33:52.700] - Dr Lemanne

So the point is that everybody needs sun. Everyone. And if you want to be healthy, if you don't have sun, you're gonna have high blood pressure, you're gonna have obesity is related to lack of sun exposure.

[00:34:03.090] - Dr Gordon

All these things have other causes as well. Breast cancer.

[00:34:06.090] - Dr Lemanne

Cancer. They are— it all plays into poor metabolic health. So to be metabolically healthy, sun exposure, to the extent that your skin accepts it, is mandatory. And I just—

[00:34:19.710] - Dr Gordon

let's throw in some brain-specific effects of it. Yes, brain.

[00:34:24.300] - Dr Lemanne

What is there about brains and sun? I bet there's a lot.

[00:34:28.060] - Dr Gordon

There is not a lot about it, but there is a lot emerging, and this is still new too, about nitric oxide. As we said previously, we've long known sunlight was a benefit. It took some time for a very brilliant scientist to figure out that it was largely mediated by at least nitric oxide, way more so than vitamin D. And as you said, there will probably be other factors. So we do know what nitric oxide does in the brain, and like the rest of the body, You have better circulation in your brain if you have nitric oxide, and the blood flow in the brain has two parts to it. It brings nutrients to the brain, and it helps with the glymphatic system fueling, which removes waste products from the brain. So the enhanced brain circulation is analogous to the systemic effects of lower blood pressure and better circulation. But there are additionally emerging details, things like spending some time in the sun increases your brain structural, let's see. So we can do MRIs now that measure the actual, I think it's cubic centimeters of your gray matter, of your white matter, of different regions of your brain.

[00:35:49.840] - Dr Gordon

And sunlight exposure acutely, even just 2 hours of sunlight exposure increases the volumes of those areas of the brain. Brain.

[00:35:58.910] - Dr Lemanne

Now it's— Wait a minute. You mean when I go out and lie in the sun, my brain's getting bigger? Yes. Oh, I don't know if I'm getting smarter, but my brain's getting bigger.

[00:36:06.750] - Dr Gordon

Yes. And they've tested it. And one of these I feel like I know about, which is that it improves alertness, it improves mood, and that's direct— that's not so much nitric oxide. Maybe it's sunlight itself enhances the neurotransmitter serotonin production. Which is why those seasonal affective disorders light boxes are popular in the wintertime for people who get depressed without the sunlight in the wintertime, directly promotes serotonin. But it does other things that we believe are more mediated by nitric oxide, enhancing attention, reducing the time it takes to learn something or acquire new information, accelerates reaction time, which is one of the things that gets slower as you get older and get neurodegenerative disease. And memory. So there are a lot of little bits and pieces of what we understand about cognitive health that are enhanced by nitric oxide, and one of the best ways to get nitric oxide is from the sun that we're celebrating today. Ah, okay.

[00:37:15.440] - Dr Lemanne

So sun exposure makes you live longer even with an increased risk of certain types of skin cancer, even with And the—

[00:37:24.310] - Dr Gordon

and it makes you smarter. Can't argue with that. I want to add something for listeners who've had a cardiovascular panel that included a marker called asymmetric dimethylarginine. I've been ordering this test for years, and I want to clarify something where I had the directionality slightly backwards. ADMA doesn't just signal that you have low nitric oxide, it actively inhibits nitric oxide nitric oxide synthase, the enzyme that makes nitric oxide. So elevated ADMA is a cause of low nitric oxide production, not merely a marker. That distinction matters because if your ADMA is high, you do want to address it, not just note it. So elevated ADMA levels actually block production of nitric oxide.

[00:38:18.730] - Dr Lemanne

Correct.

[00:38:19.850] - Dr Gordon

Two other things worth knowing Even mildly reduced kidney function, a GFR your doctor might not flag as a problem, tends to raise and therefore suppress nitric oxide production throughout the body, including the brain.

[00:38:35.960] - Dr Lemanne

And a lot of us walk around with borderline kidney function, and we have no idea that it's a problem because we're urinating plenty, and we think that's how kidney function is measured.

[00:38:45.890] - Dr Gordon

And some people carry genetic variants in nitric oxide synthase gene itself that reduce their baseline production independently. So if you have cardiovascular risk factors or early kidney function decline, ADMA is worth specifically requesting on a panel. We'll put a reference to that in the show notes.

[00:39:08.850] - Dr Lemanne

And the lifestyle factors that lower ADMA are essentially the same ones that raise nitric oxide, like sunlight, beets, Dark leafy greens and outdoor time.

[00:39:19.050] - Dr Gordon

Yeah, that's exactly. So again, full circle brings us right back to the sun.

[00:39:24.430] - Dr Lemanne

I can think of an easy way to know if you are, if sunlight is affecting you. Take your blood pressure before and after a sun bath. Because what does, that's what sunlight does. It's, hypertension is not fixed by replacing vitamin D. That's not the problem. It's something else in sun. And that something else is blocked by clothing, by— it's not the UV, the infrared light that is not blocked by clothing, but UV is blocked by clothing and by sunscreen. And I cover my face too. It's a little too late for me as well, but I do cover my face when I'm sunbathing somewhat. I'm not as, as thick as I should be. But in any case, the nitric oxide, when you're exposing your skin to sun, causes blood vessels to relax. What is hypertension? It's blood vessels all squeezed up tight trying to get the blood to all these tough places to get it to, 'cause the blood, the whole blood vessel system is really stiff. So nitric oxide relaxes that immediately. And so taking your blood pressure before you go out and sunbathe and immediately after should tell you whether you're on the right track with that.

[00:40:33.210] - Dr Lemanne

I would actually take it while I was sunbathing and watch it go down. Okay, yes.

[00:40:37.040] - Dr Gordon

You said you would do it as if you were.

[00:40:38.360] - Dr Lemanne

I would probably do it when I was, I don't have high blood pressure, but if I did, I would take my blood pressure while I'm sunbathing, and as soon as it gets down to where it needs to be, I can go in.

[00:40:45.980] - Dr Gordon

But then does it go back up again?

[00:40:47.990] - Dr Lemanne

If you don't sunbathe enough, yes. You have to relax those blood vessels. Another thing that does that is sauna and contrast therapy. That gives your blood vessels a good workout. They relax, they contract, they relax, they contract as you go in the heat, the cold, the heat, the cold, respectively.

[00:41:03.000] - Dr Gordon

So people should know, just as is true about all this, everything is multifactorial. So there is high blood pressure, that is caused separately from vasoconstriction, and that is the kind where there's induration in the walls of the little blood vessels so that a normal amount of vasoconstriction is more hazardous if you tend to have an inflammatory environment in the blood vessels themselves, which is genetically lifestyle controlled. So you can't just say, "I'm gonna quit my blood pressure medicine and lie out in the sun." Oh, please don't.

[00:41:39.150] - Dr Lemanne

No, I say take your blood pressure and figure out the things in your life that lower it. Other things that increase blood pressure for a lot of people are starchy foods. I think people don't realize that some people are better off just taking a spoonful of table sugar than they are eating a piece of bread or some noodles or a cake, because— or potatoes. Starchy food for a lot of people is a cause of high blood pressure, and they drop the starch and their blood pressure is back to normal.

[00:42:04.290] - Dr Gordon

Can you explain that to me?

[00:42:06.770] - Dr Lemanne

I cannot, but I think you're in— I think it was really interesting what you said about the basically, you were talking about edema of the microvasculature. So the microvasculature gets beady and swollen, just like people have swollen ankles. There are people who have swelling in the walls of their tiniest arteries, just before they become veins.

[00:42:25.440] - Dr Gordon

That's really interesting. And it's partially mediated by aldosterone, which some people make more of than others. And so that— again, I'm going back to my Maybe we'll have a whole talk sometime. Maybe we'll have my genetics consultant, see if she'd be a guest sometime on the show. But I did this big genetics evaluation a decade or so ago out of curiosity why I, who was thinner and more fit at that point than I am now, and my mother, who was always thin and relatively fit, why did we get high blood pressure? And there's a gene— And it wasn't a lack of sunlight. And it was not a lack of sunlight for either one of us. And I have a gene that means unchecked I will make more aldosterone than the average bear. So if I had high blood pressure, the medicine that would meet that need, and it is definitely keeping my aldosterone, my blood pressure lower, is a different diuretic than the common ones used. So the common ones are hydrochlorothiazide, and the ones that address aldosterone is one called spironolactone. And each of these has different benefits and adverse effects and secondary effects that a proper physician will monitor when you're on those medications.

[00:43:47.050] - Dr Lemanne

But it's complicated. It's always complicated in a delightful way to talk to you.

[00:43:53.610] - Dr Gordon

It is always great to talk to you. And I loved looking more. I thought I was fairly savvy about nitric oxide, but I learned a lot looking into it more, stimulated by some sunlight, I'm sure.

[00:44:09.490] - Dr Lemanne

I enjoyed looking into this as well, and the long list of cancers related to indoor life is quite sobering. And the list of cancers related to lack of sunlight and the causes, the numbers of deaths related to lack of sunlight compared to the very few deaths related to Excess sunlight, melanoma specifically I'm talking about, very orders of magnitude difference.

[00:44:35.020] - Dr Gordon

And I— could you mention that to the dermatologist when you see them next week?

[00:44:40.160] - Dr Lemanne

Oh, I can, yeah.

[00:44:41.760] - Dr Gordon

See if they could pass it along to their colleagues. Anyway, this has been great, and maybe it's time for us to go outside and catch a little sunlight.

[00:44:49.800] - Dr Lemanne

Yeah, and maybe it's higher than 64,960 now. It's a little— the sun's a little higher in the sky.

[00:44:55.110] - Dr Gordon

Sun's a little higher in the sky. Thanks so much for today. Good talking to you.

[00:44:58.280] - Dr Lemanne

Good talking to you. Bye. Bye. If you haven't already, please take a moment to subscribe. Your simple click is not abstract. It's not anonymous. To us, it's very real. It helps us reach more patients and physicians to challenge the old ways of thinking about health and to keep these evidence-based conversations going. Hitting that subscribe button actually makes a huge difference, and thank you.

[00:45:25.630] - Dr Gordon

You have been listening to the Lemanne-Gordon podcast where docs docstalkshop.com.

[00:45:31.260] - Dr Lemanne

For podcast transcripts, episode notes and links, and more, please visit the podcast website at docstalkshop.com. Happy eavesdropping. Everything presented in this podcast is for educational and informational purposes only and should not be construed as medical advice. No doctor-patient relationship is established or implied. If you have a health or a medical concern, see a qualified professional promptly.

[00:45:59.050] - Dr Gordon

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[00:46:10.840] - Dr Lemanne

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[00:46:25.330] - Dr Gordon

Again, if you have any medical concerns, see your own provider or another qualified health professional promptly.

[00:46:32.170] - Dr Lemanne

You must not take any action based on information in this podcast without first consulting your own qualified medical professional. Everything on this podcast, including music, dialogue, and ideas, is copyrighted by docstalkshop.com.

[00:46:47.900] - Dr Gordon

docstalkshop.com is recorded at Freeman Sound Studio in Ashland, Oregon.

[00:46:53.600] - Dr Lemanne

Hey, Deborah, you remember that light episode we did? I do. Tom and I measured the light outdoors right after that episode. You'd already gone, but it was about noon and the clouds had cleared. It was a cloudy day when I measured the 65,000 or whatever it was lux before our episode. But when we finished, it was bright sun and it was near noon and it was near summer solstice.

[00:47:17.140] - Dr Gordon

Oh, I'd be curious to know what was the reading under those conditions. Oh, hang on.

[00:47:23.090] - Dr Lemanne

100,000 lux. I'll drink to that note.