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

87,914 views ・ 2013-01-17

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Translator: Morton Bast Reviewer: Thu-Huong Ha
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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)
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