Could the sun be good for your heart? - Richard Weller

So before I became a dermatologist, I started in general medicine, as most dermatologists do in Britain. At the end of that time, I went off to Australia about 20 years ago. What you learn when you go to Australia is that the Australians are very competitive, and they are not magnanimous in victory. That happened a lot. I knew Pommies; you can't play cricket, rugby. I could accept that, but moving into work, we have each week what's called a journal club, where you'd sit down with the other doctors and you'd study a scientific paper in relation to medicine.

After week one, it was about cardiovascular mortality, a dry subject. How many people die of heart disease? What are the rates? They were competitive about this. "You Pommies, your rates of heart disease are shocking," and of course they were right. Australians have about one-third less heart disease than we do: fewer deaths from heart attacks, heart failure, and strokes. They're generally a healthier bunch. Of course, they said this was because of their fine moral standing, their exercise, because they're Australians and we're easy Pommies and so on.

But you know, it's not just Australia that has better health than Britain. Within Britain, there is a gradient of health, and this is what's called standardized mortality, basically your chances of dying. This is looking at data from the paper about 20 years ago, but it's true today. Comparing your rates of dying at 50 degrees north—that's the south, that's London and places—by latitude and 55 degrees, the bad news is that's here in Glasgow. I'm from Edinburgh. Worst news? That's even Edinburgh.

So there is... what accounts for this horrible space here between us up here in southern Scotland and the south? Now we know about smoking, deep-fried Mars bars, trips—the Glasgow diet—all of these things, but this graph is after taking into account all of these known risk factors. This is after accounting for smoking, social class, diet, and all those other known respects. We are left with this missing space of increased deaths the further north you gaze.

Now sunlight, of course, comes into this, and vitamin D has had a great deal of press. A lot of people get concerned about it, and we need vitamin D. It's now a requirement that children have a certain amount. My grandmother grew up in Glasgow back in the 1920s and '30s when rickets was a real problem, and cod liver oil was brought in. That really prevented the rickets that used to be common in this city. I, as a child, was fed cod liver oil by my grandmother. Nobody forgets cod liver oil.

But an association: the higher people's blood levels of vitamin D are, the less heart disease they have, the less cancer. There seems to be a lot of data suggesting that vitamin D is very good for you, and it is to prevent rickets and so on. But if you give people vitamin D supplements, you don't change that high rate of heart disease, and the evidence for it preventing cancers is not yet great. So what I'm going to suggest is that vitamin D is not the only story in town. It's not the only reason preventing heart disease. High vitamin D levels I think are a marker for sunlight exposure, and sunlight exposure, in methods I'm going to show, is good for heart disease.

Anyway, I came back from Australia and, despite the obvious risks to my health, I moved to Aberdeen. Now in Aberdeen, I started my dermatology training, but I also became interested in research and, in particular, I became interested in this substance: nitric oxide. Now these three guys up here first got big marrow, Murad won the Nobel Prize for medicine back in 1998, and they were the first people to describe this new chemical transmitter, nitric oxide.

What nitric oxide does is it dilates blood vessels, so it lowers your blood pressure. It also dilates the coronary arteries, stops angina. What was remarkable about it was in the past, when we thought of chemical messengers in the body, we thought of complicated things like estrogen and insulin or nerve transmission—very complex processes with very complex chemicals that fit into very complex receptors. And here's this incredibly simple molecule: a nitrogen and an oxygen that have stuck together, and yet these are hugely important for painting our low blood pressure, for neurotransmission, for many many things, but particularly cardiovascular health.

I started doing research, and we found, very excitingly, that the skin produces nitric oxide. So it's not just in the cardiovascular system that it arises; it arises in the skin. While having found that and published that, I thought, well, what's it doing? How do you have a low blood pressure in your skin? You know it's not the heart. What do you do? So I went off to the States, as many people do if they're going to do research, and I spent a few years in Pittsburgh.

This is Pittsburgh, and I was interested in these really kind of complex systems. We thought that maybe nitric oxide affected cell death and how cells survive and their resistance to other things. I first of all started working in cell culture, growing cells, and then using knockout mouse models—mice that couldn't make me the gene. We worked out a mechanism that I know was helping cells survive.

I then moved back to Edinburgh, and in Edinburgh, the experimental animal we use is the medical student. It's a species close to humans with several advantages over mice: they’re free, you don't shave them, they feed themselves, and nobody pickets your office saying, "Save the lab medical student." So they're really an ideal model.

But what we found was that we couldn't reproduce in man the data we had shown in mice. It seemed we couldn't turn off the production of nitric oxide in the skin of humans. We put on creams that block the enzyme that made it and we injected things; we couldn't turn off the nitric oxide. The reason for this, it turned out after two or three years of work, was in the skin we have huge stores not of nitric oxide because nitric oxide is a gas, and it's released and in a few seconds it's away, but it can be turned into these forms of nitric oxide: nitrate (NO3), nitrite (NO2).

Might raise with us, and these are more stable. Your skin has got really large stores of Na, and we then thought to ourselves, all those big stores, I wonder if sunlight might activate those stores and release them from the skin, where the stores are about ten times as big as what's in the circulation? Could the sun activate those stores into circulation? And then in circulation, it can do good things for your cardiovascular system.

Well, I'm an experimental dermatologist, so what we did was we thought we have to expose our experimental animals to sunlight. So what we did was we took a bunch of volunteers and we exposed them to ultraviolet light. These are kind of sun lamps. Now what we were careful to do was vitamin D is made by ultraviolet B rays, and we wanted to separate our story from the vitamin D story, so we used ultraviolet A, which doesn't make vitamin D.

When we put people under a lamp for the equivalent of about 30 minutes of sunshine in summer in Edinburgh, what we produced was a rise in circulating nitric oxide. So we put patients with these subjects under the UV and then NO levels do go up, and their blood pressure goes down—not by much at an individual level, but enough at a population level to shift the rates of heart disease in a whole population. When we shone UV at them, or when we warmed them up to the same level as the lamps but didn't actually let the rays hit the skin, this didn't happen.

So this seems to be a feature of ultraviolet rays hitting the skin. Now we're still collecting data, a few good things here where this appeared to be more marked in older people. I'm not sure exactly how much; one of the subjects here was my mother-in-law, and clearly I do not know her age, but certainly in people older than my wife, this appears to be a more marked effect. The other thing I should mention was there was no change in vitamin D. This is separate from vitamin D, so vitamin D is good for you; it stops rickets, it provides calcium, and that's important stuff, but this is a separate mechanism from vitamin D.

Now one of the problems in looking at blood pressure is your body does everything it can to keep your blood pressure at the same place. If your leg is chopped off and you lose blood, your body will clamp down, increase the heart rate, do everything it can to keep your blood pressure up. That is an absolutely fundamental physiological principle.

So what we've next done is we've moved on to looking at blood vessel dilatation. So we've measured—this is again noticeable, no tail and hairless—this is a medical student. In the arm, you can measure how blood flow in the arm by how much it swells up as blood flows into it, and what we've shown is adding a sham irradiation—this is the thick line here; this is shining UV on the arms that warms them up but keeping it covered so the rays don't hit the skin—there is no change in blood flow or in the dilatation of the blood vessels.

But the act of irradiation during the UV, and for an hour after it, there is dilation of the blood vessels. This is the mechanism by which you lower blood pressure, by which you dilate the coronary arteries, also to let the blood supply the heart. So here is further data that ultraviolet, that sunlight, has benefits on the blood flow and the cardiovascular system.

So we thought we were just kind of modeling at different amounts of UV hitting the earth at different parts of the earth at different times of year. So you can actually work out those stores of nitric oxide, the nitrates and nitrites, might rise from the skin and release the N-O. Different wavelengths of light have different activities of doing that, so you can look at the wavelengths that like to do that.

You can look—if you live on the equator, the sun comes straight overhead. It comes through a very thin bit of atmosphere and, whether in winter or summer, it's the same amount of light. If you live up here in the summer, the sun comes fairly directly down, but in winter, it's coming through a huge amount of atmosphere, and much of the ultraviolet is weeded out. And that range of wavelengths to the earth is different in summer to winter.

So what you can do is you can multiply those data by the N-O that’s released, and you can calculate how much nitric oxide would be released from the skin into the circulation. Now, if you're on the equator, here are these two lines: the red line and the purple line. The amount of nitric oxide that's released is the area under the curve—the area in this space here.

So if you're on the equator, December or June, you've got masses of NO being released from the skin. Southern California in summer, you might as well be at the equator—it's great! Lots of NO is released. But for interior midwinter, well, there's still a decent amount, but Edinburgh in summer, the area beneath the curve is really good, but Edinburgh in winter, you know the amount of NO that can be released is next to nothing—tiny amounts.

So what do we think? We're still working at this story; we're still developing it, expanding it. We think it's very important, and we think it probably accounts for a lot of the north-south health divide within Britain. It's of relevance to us; we think that the skin—well, we know that the skin has got very large stores of nitric oxide as well as various other forms. We suspect a lot of these come from diet; green leafy vegetables, beet roots, lettuce has a lot of these nitric oxides that we think go to the skin.

We think they're then stored in the skin, and we think sunlight releases this, where it has generally beneficial effects. This is ongoing work, but I mean dermatologists—I'm a dermatologist. My day job is saying to people, "You've got skin cancer; it's caused by sunlight; don't go in the sun." I actually think a far more important message is that there are benefits as well as risks to sunlight. Yes, sunlight is the major alterable risk factor for skin cancer, but deaths from heart disease are a hundred times higher than deaths from skin cancer.

I think that we need to be more aware of that, and we need to find the risk-benefit ratio: how much sunlight is safe? How can we finesse this best for our general health? So thank you very much indeed.