Enjoying a little sunshine may not be as bad for you as people think. Research from the scientist who alerted the world to its role in skin cancer has suggested that its health benefits may outweigh the risks.

The hazards of moderate sunbathing have probably been exaggerated, according to a study that shows how sunlight’s effect of boosting vitamin D production may actually protect the body against cancer.

While ultraviolet (UV) light from the Sun is the chief cause of malignant melanoma, the deadliest form of skin cancer, the new work from the US shows that synthesis of vitamin D can compensate in other ways.

The vitamin appears to protect against tumours of the breast, lung, colon and prostate, the study found. The overall effect of sunshine on cancer risk may therefore be positive.

The findings come from a team headed by Richard Setlow, of the Brookhaven National Laboratory in New York, who played a leading role in establishing that UV radiation can damage DNA and cause melanoma.

Though Dr Setlow still considers sunlight a serious health risk, and advises people to protect themselves against excessive UV exposure, his new data show that it can also have health benefits because of vitamin D.

The work could lead to new formulations for sunscreen, so that it filters out harmful UVA radiation that can trigger melanoma, while allowing through more of the UVB radiation that stimulates vitamin D production. It does not suggest that sunbeds are safe, as these rely on UVA radiation.

Though many people regard a tan as healthy, medical opinion changed in the 1950s and 1960s when sunlight’s role in skin cancer was discovered. Dr Setlow led much of the key research.

Public health campaigns have since encouraged people to cover up or wear sunscreen when exposed to direct sunlight. In Britain, 8,900 new cases of melanoma are diagnosed annually and it causes 1,800 deaths.

However, some scientists have begun to question whether safety advice is too extreme. While the link to melanoma is not disputed, sunlight is also the principal source of vitamin D, which research suggests improves prognosis in many cancers. It may even help the body to fight melanoma.

In his latest study, published in the Proceedings of the National Academy of Sciences, Dr Setlow calculated vitamin D synthesis at different latitudes. People living near the equator in Australia produce 3.4 times more vitamin“ D in response to sunlight than UK residents. Incidence of all skin cancers also increases towards the equator.

The scientists also found that incidence rates for other cancers, such as breast, lung and prostate, increased from north to equator too. When they examined survival rates, however, they found that people exposed to more sunlight had a better prognosis.

Dr Setlow said: “In previous work, we have shown that survival rates for these cancers improve when the diagnosis coincides with the season of maximum sun exposure.”

Joanna Owens, senior science information officer for Cancer Research UK, said: “A little bit of sun goes a long way. The amount of exposure you need to top up your vitamin D is always less than the amount needed to tan or burn, which increases the risk of skin cancer.”

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