Is sun exposure actually good for you? (Part 2)

May 24, 2020 / Duncan Fisher
The nitric oxide question

We published a few weeks ago on one possible reason for the pretty clear benefits of sunlight on your skin. We have said many times that a little sun exposure, as long as it’s not overdone, is good for you. One reason is the vitamin D connection, and that was the substance of our little blog post.

We promised another post, and this is it, on the nitric oxide pathway, a second way that sunlight – again, limited sunlight – appears to be able to do good things for you.

This won’t change any of the sun-exposure rules that help protect you from sunburn and skin cancer. It’s still true, as it always was, that too much sun is bad for you, even dangerous.

But there is this very interesting fund of data, about natural nitric oxide, that helps explain why there are more health benefits of sun exposure than we used to think.

Dr Richard Weller, of Edinburgh University, is at the forefront of research into this. In 1996 he made the first description of nitric oxide production on the skin surface. There had been recent Nobel Prize work that showed how nitric oxide dilated blood vessels and thus helped regulate blood pressure. There is a known geographical correlation between lower blood pressure and sunnier climates, which may have something to do with this.

But nitric oxide was also suspected to be involved in other physiological functions too. Dr Weller and teams in the UK, Germany, and the US began chasing these, starting by studying the effects of nitric oxide on skin cell survival after sun exposure. They were able to show slowed death rates in keratinocytes, a type of skin cell, in laboratory dishes and mice, though they were unable to replicate this effect in humans. Carrying the work forward in a different way, they were able to show that human skin contains large stores of nitrogen oxides (NOx), which are photo-reduced by UV radiation, which in turn releases nitric oxide into circulation … after which comes that known mechanism of action that lowers blood pressure.

Work in the field has since expanded. The sun-mediated nitric oxide pathway turns out to have a role in even more regulatory processes. Whole-body UV exposure combined with oral nitrates has been shown to improve the performance of trained cyclists, and nitric oxide with UV light may be what appears to suppress obesity and metabolic syndrome in high-fat-diet lab rats.

Studies like this don’t mean you can sunbathe your way to a swimsuit body, or to victory in the Tour de France. But they’re clues about how, through the medium of cutaneous nitric oxide, a bit of sunlight has its benefits. The newest line of investigation to show promise these days is in cardiovascular health. The field keeps expanding.

Overall, the data are now generally encouraging enough that the risk-benefit ratio for sunlight exposure is beginning to be re-examined in Europe, Australia, and the United States.

This will never mean, to say it once more, that baking in the sun is good for you. But it does mean that a bit of sunlight, through at least 2 mechanisms of action, is indeed good for you. If it’s any illustration of the medical community’s acceptance of the idea, you can now buy an over-the-counter sunscreen that protects you from ultraviolet radiation but at the same time allows normal release of nitric oxide from sun-exposed skin.

To say it the way we did in our vitamin D post, we won’t retract any of our burn and cancer warnings, but we will say that sunshine, in sensible amounts, is actually a very good thing. And now we know more about why.

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