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So, before I became a dermatologist,

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I started in general medicine,

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as most dermatologists do in Britain.

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At the end of that time, I went off to Australia,

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about 20 years ago.

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What you learn when you go to Australia

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is the Australians are very competitive.

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And they are not magnanimous in victory.

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And that happened a lot:

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"You pommies, you can't play cricket, rugby."

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I could accept that.

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But moving into work --

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and we have each week what's called a journal club,

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when you'd sit down with the other doctors

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and you'd study a scientific paper

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in relation to medicine.

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And after week one, it was about cardiovascular mortality,

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a dry subject -- how many people die of heart disease,

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what the rates are.

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And they were competitive about this:

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"You pommies, your rates of heart disease are shocking."

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And of course, they were right.

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Australians have about a third less heart disease than we do --

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less deaths from heart attacks, heart failure, less strokes --

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they're generally a healthier bunch.

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And of course they said this was because of

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their fine moral standing, their exercise,

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because they're Australians and we're weedy pommies, and so on.

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But it's not just Australia that has better health than Britain.

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Within Britain, there is a gradient of health --

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and this is what's called standardized mortality,

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basically your chances of dying.

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This is looking at data from the paper about 20 years ago,

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but it's true today.

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Comparing your rates of dying 50 degrees north --

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that's the South, that's London and places --

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by latitude, and 55 degrees --

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the bad news is that's here, Glasgow.

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I'm from Edinburgh. Worse news, that's even Edinburgh.

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(Laughter)

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So what accounts for this horrible space here

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between us up here in southern Scotland

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and the South?

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Now, we know about smoking,

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deep-fried Mars bars, chips -- the Glasgow diet.

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All of these things.

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But this graph is after taking into account

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all of these known risk factors.

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This is after accounting for smoking, social class, diet,

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all those other known risk factors.

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We are left with this missing space

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of increased deaths the further north you go.

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Now, sunlight, of course, comes into this.

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And vitamin D has had a great deal of press,

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and a lot of people get concerned about it.

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And we need vitamin D. It's now a requirement that children have a certain amount.

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My grandmother grew up in Glasgow,

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back in the 1920s and '30s when rickets was a real problem

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and cod liver oil was brought in.

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And that really prevented the rickets that used to be common in this city.

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And I as a child was fed cod liver oil by my grandmother.

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I distinctly -- nobody forgets cod liver oil.

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But an association: The higher people's blood levels of vitamin D are,

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the less heart disease they have, the less cancer.

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There seems to be a lot of data suggesting that vitamin D is very good for you.

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And it is, to prevent rickets and so on.

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But if you give people vitamin D supplements,

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you don't change that high rate of heart disease.

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And the evidence for it preventing cancers is not yet great.

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So what I'm going to suggest is that vitamin D is not the only story in town.

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It's not the only reason preventing heart disease.

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High vitamin D levels, I think, are a marker for sunlight exposure,

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and sunlight exposure, in methods I'm going to show,

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is good for heart disease.

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Anyway, I came back from Australia,

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and despite the obvious risks to my health, I moved to Aberdeen.

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(Laughter)

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Now, in Aberdeen, I started my dermatology training.

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But I also became interested in research,

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and in particular I became interested in this substance, nitric oxide.

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Now these three guys up here,

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Furchgott, Ignarro and Murad,

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won the Nobel Prize for medicine back in 1998.

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And they were the first people to describe

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this new chemical transmitter, nitric oxide.

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What nitric oxide does is it dilates blood vessels,

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so it lowers your blood pressure.

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It also dilates the coronary arteries, so it stops angina.

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And what was remarkable about it

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was in the past when we think of chemical messengers within the body,

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we thought of complicated things like estrogen and insulin,

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or nerve transmission.

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Very complex processes with very complex chemicals

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that fit into very complex receptors.

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And here's this incredibly simple molecule,

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a nitrogen and an oxygen that are stuck together,

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and yet these are hugely important for [unclear] our low blood pressure,

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for neurotransmission, for many, many things,

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but particularly cardiovascular health.

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And I started doing research, and we found, very excitingly,

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that the skin produces nitric oxide.

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So it's not just in the cardiovascular system it arises.

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It arises in the skin.

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Well, having found that and published that,

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I thought, well, what's it doing?

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How do you have low blood pressure in your skin?

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It's not the heart. What do you do?

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So I went off to the States, as many people do if they're going to do research,

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and I spent a few years in Pittsburgh. This is Pittsburgh.

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And I was interested in these really complex systems.

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We thought that maybe nitric oxide affected cell death,

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and how cells survive, and their resistance to other things.

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And I first off started work in cell culture, growing cells,

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and then I was using knockout mouse models --

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mice that couldn't make the gene.

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We worked out a mechanism, which -- NO was helping cells survive.

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And I then moved back to Edinburgh.

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And in Edinburgh, the experimental animal we use is the medical student.

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It's a species close to human,

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with several advantages over mice:

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They're free, you don't shave them, they feed themselves,

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and nobody pickets your office saying,

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"Save the lab medical student."

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So they're really an ideal model.

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But what we found

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was that we couldn't reproduce in man the data we had shown in mice.

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It seemed we couldn't turn off the production

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of nitric oxide in the skin of humans.

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We put on creams that blocked the enzyme that made it,

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we injected things. We couldn't turn off the nitric oxide.

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And the reason for this, it turned out, after two or three years' work,

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was that in the skin we have huge stores

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not of nitric oxide, because nitric oxide is a gas,

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and it's released -- (Poof!) -- and in a few seconds it's away,

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but it can be turned into these forms of nitric oxide --

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nitrate, NO3; nitrite, NO2; nitrosothiols.

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And these are more stable,

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and your skin has got really large stores of NO.

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And we then thought to ourselves, with those big stores,

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I wonder if sunlight might activate those stores

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and release them from the skin,

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where the stores are about 10 times as big as what's in the circulation.

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Could the sun activate those stores into the circulation,

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and there in the circulation do its good things for your cardiovascular system?

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Well, I'm an experimental dermatologist,

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so what we did was we thought

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we'd have to expose our experimental animals to sunlight.

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And so what we did was we took a bunch of volunteers

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and we exposed them to ultraviolet light.

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So these are kind of sunlamps.

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Now, what we were careful to do was,

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vitamin D is made by ultraviolet B rays

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and we wanted to separate our story from the vitamin D story.

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So we used ultraviolet A, which doesn't make vitamin D.

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When we put people under a lamp

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for the equivalent of about 30 minutes of sunshine in summer in Edinburgh,

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what we produced was, we produced a rise

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in circulating nitric oxide.

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So we put patients with these subjects under the UV,

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and their NO levels do go up,

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and their blood pressure goes down.

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Not by much, as an individual level,

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but enough at a population level

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to shift the rates of heart disease in a whole population.

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And when we shone UV at them,

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or when we warmed them up to the same level as the lamps,

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but didn't actually let the rays hit the skin, this didn't happen.

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So this seems to be a feature of ultraviolet rays hitting the skin.

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Now, we're still collecting data.

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A few good things here:

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This appeared to be more marked in older people.

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I'm not sure exactly how much.

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One of the subjects here was my mother-in-law,

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and clearly I do not know her age.

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But certainly in people older than my wife,

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this appears to be a more marked effect.

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And the other thing I should mention

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was there was no change in vitamin D.

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This is separate from vitamin D.

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So vitamin D is good for you -- it stops rickets,

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it prevents calcium metabolism, important stuff.

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But this is a separate mechanism from vitamin D.

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Now, one of the problems with looking at blood pressure

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is your body does everything it can

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to keep your blood pressure at the same place.

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If your leg is chopped off and you lose blood,

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your body will clamp down, increase the heart rate,

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do everything it can to keep your blood pressure up.

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That is an absolutely fundamental physiological principle.

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So what we've next done

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is we've moved on to looking at blood vessel dilatation.

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So we've measured -- this is again,

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notice no tail and hairless, this is a medical student.

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In the arm, you can measure blood flow in the arm

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by how much it swells up as some blood flows into it.

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And what we've shown is that doing a sham irradiation --

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this is the thick line here --

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this is shining UV on the arm so it warms up

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but keeping it covered so the rays don't hit the skin.

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There is no change in blood flow, in dilatation of the blood vessels.

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But the active irradiation,

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during the UV and for an hour after it,

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there is dilation of the blood vessels.

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This is the mechanism by which you lower blood pressure,

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by which you dilate the coronary arteries also,

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to let the blood be supplied with the heart.

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So here, further data that ultraviolet -- that's sunlight --

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has benefits on the blood flow and the cardiovascular system.

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So we thought we'd just kind of model --

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Different amounts of UV hit different parts of the Earth at different times of year,

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so you can actually work out those stores of nitric oxide --

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the nitrates, nitrites, nitrosothiols in the skin --

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cleave to release NO.

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Different wavelengths of light have different activities of doing that.

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So you can look at the wavelengths of light that do that.

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And you can look -- So, if you live on the equator, the sun comes straight overhead,

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it comes through a very thin bit of atmosphere.

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In winter or summer, it's the same amount of light.

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If you live up here, in summer

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the sun is coming fairly directly down,

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but in winter it's coming through a huge amount of atmosphere,

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and much of the ultraviolet is weeded out,

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and the range of wavelengths that hit the Earth

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are different from summer to winter.

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So what you can do is you can multiply those data

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by the NO that's released

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and you can calculate how much nitric oxide

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would be released from the skin into the circulation.

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Now, if you're on the equator here --

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that's these two lines here, the red line and the purple line --

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the amount of nitric oxide that's released is the area under the curve,

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it's the area in this space here.

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So if you're on the equator, December or June,

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you've got masses of NO being released from the skin.

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So Ventura is in southern California.

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In summer, you might as well be at the equator.

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It's great. Lots of NO is released.

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Ventura mid-winter, well, there's still a decent amount.

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Edinburgh in summer, the area beneath the curve is pretty good,

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but Edinburgh in winter, the amount of NO that can be released

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is next to nothing, tiny amounts.

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So what do we think?

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We're still working at this story,

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we're still developing it, we're still expanding it.

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We think it's very important.

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We think it probably accounts for a lot of the north-south health divide within Britain,

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It's of relevance to us.

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We think that the skin --

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well, we know that the skin has got very large stores

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of nitric oxide as these various other forms.

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We suspect a lot of these come from diet,

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green leafy vegetables, beetroot, lettuce

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has a lot of these nitric oxides that we think go to the skin.

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We think they're then stored in the skin,

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and we think the sunlight releases this

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where it has generally beneficial effects.

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And this is ongoing work, but dermatologists --

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I mean, I'm a dermatologist.

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My day job is saying to people, "You've got skin cancer,

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it's caused by sunlight, don't go in the sun."

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I actually think a far more important message

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is that there are benefits as well as risks to sunlight.

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Yes, sunlight is the major alterable risk factor for skin cancer,

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but deaths from heart disease are a hundred times higher

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than deaths from skin cancer.

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And I think that we need to be more aware of,

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and we need to find the risk-benefit ratio.

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How much sunlight is safe,

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and how can we finesse this best for our general health?

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So, thank you very much indeed.

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(Applause)