Dermatologists have long stressed the importance of sun protection, primarily to reduce the effects of skin ageing and the risk of skin cancer, yet exposure to sunlight is necessary for vitamin D production and has a positive effect on our mood. Adequate levels of vitamin D also reduce the risk of several types of cancer, including melanoma, so, as ever, it's important to find a healthy balance.

The link between sun exposure and skin cancer

If we count all types, skin cancer is the most common type of cancer in the world. (1) Everyone has heard that UV rays from the sun can damage the skin; sunlight is likely responsible for a significant percentage of skin cancers. (2,3)

Interestingly, however, the link is not so clear-cut for melanoma: quite a lot of research suggests that people who work outdoors and get the most sunlight are the ones who are most protected. (4,5,6) One study found that people who were exposed to more UV radiation had a lower risk of melanoma. (9) Conversely, "intermittent" sun exposure, where you only go out in the sun occasionally, increases the risk of melanoma significantly. (4,5,7)

The incidence of melanoma is much higher in Nordic countries such as Sweden and Finland than in Mediterranean countries, where people are exposed to much more sunlight. (8)

Although tanning bed use may slightly increase the risk of melanoma, the magnitude of this increase is small compared to genetic factors. (10) In addition, melanoma can develop in parts of the body that are not exposed to sunlight at all, such as the oral cavity or nose. (11)

These data suggest that avoiding sunlight altogether is not necessarily a good idea, but it is important to prevent sunburn. 

The role of vitamin D

Over the past decades, there has been growing evidence that vitamin D plays an important role in the prevention of various chronic diseases, including several types of cancer. (12,13)

Melanoma is no exception, and the studies cited so far suggest that people who work outdoors are less likely to develop the disease because they have a better vitamin D intake and their skin is used to sunlight, making it harder for them to burn. Mediterranean countries have more hours of sunshine, which, though resulting in stronger UV radiation, also favors vitamin D production through the angle of incidence of the sun.

One study found that people who were deficient in vitamin D were less likely to survive melanoma than those who had a favorable pre-supply or who subsequently managed to normalize their vitamin levels.(14)

Important to supplement

A relatively recent study in Finland found that those who regularly supplemented with vitamin D3 were less than half as likely to develop melanoma. (15)

The levels of stored vitamin D (calcidiol/25-OHD) were analyzed in half of the patients and were in line with those expected from vitamin D supplementation - the study authors were thus confident that the subjects were indeed supplementing and that it was not a coincidence.

Fortunately, these days we don't need to rely solely on sunshine for vitamin D production - we'd be in a lot of trouble, as we get almost no sunlight at all for much of the year in Europe. However, supplements can help ensure adequate levels of vitamin D without exposing our skin to excessive UV radiation.

Reasonable sun exposure has a number of benefits beyond vitamin supplementation, including improving well-being and reducing the risk of several chronic diseases. Avoid sunburn and overexposure to the sun and feel free to spend time outdoors. (16)