Sunshine is regularly blamed for causing fatal skin cancers, but it may help save your life if you develop a different cancer. It seems that sunlight has an overall protective effect as it stimulates the body’s production of vitamin D, which helps to combat internal cancers, including those of the colon and prostate.
“A little sun exposure is a little better for you than avoiding sunlight,” says Richard Setlow of Brookhaven National Laboratory in Upton, New York, who co-led the new work. “Vitamin D doesn’t lower the incidence of internal cancers, but it prevents more people dying from them.”
“Vitamin D doesn’t lower the incidence of internal cancers, but it prevents more people dying from them”
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The team examined global numbers of cancer cases and survival rates, and how they varied with the intensity of sunlight at different latitudes. On balance, sunlight was found to save more lives than it takes because people in sun-drenched regions are protected from certain cancers by vitamin D – but the benefit varies with location. Survival rates from colon, prostate, lung and breast cancer are between 20 and 50 per cent higher in sunny countries near the equator, such as Australia, than in shadier northern countries such as Norway, even though the rate of cases is similar (Proceedings of the National Academy of Sciences, ).
Others caution against relaxing current advice, which is to cover up in the sun. “I’m very concerned about UV radiation being seen as the mode of delivering or rescuing vitamin D levels,” says David Fisher, director of the melanoma programme at Harvard Medical School in Boston, Massachusetts. “UV’s known carcinogenic effects make this untenable.”
Richard Gallagher of the British Columbia Cancer Agency in Vancouver, Canada, adds that improved survival rates might be down to factors other than vitamin D, such as better cancer screening programmes. A compromise would be to take vitamin D supplements, he says.
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