Sunscreens, vitamin D and cancer

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I can tell we have emerged from the depths of winter by the cheery presence of daffodils and the fact that PR companies have started sending me sunscreen samples along with gloomy statistics about the rising rates of skin cancer in the UK. However, while sunscreen use seems like an obvious way to protect against skin cancer, recent evidence has come to light which has cast a shadow over this practice. Although sunscreens do seem to help prevent the development of a usually treatable form of skin cancer known as squamous cell carcinoma, two studies have found that their use is associated with a substantially increased risk of the often-deadly condition known as malignant melanoma. It seems that the widely-recommended use of sunscreens to guard against this most serious form of skin cancer may not be such a bright idea after all.

While the precise explanation for the apparent link between sunscreen use and increased melanoma risk are unknown, scientists are keen to shed some light on this paradox. One theory is that while sunscreen may help to block out the part of the sun’s spectrum that causes burning, its use may at the same time prolong exposure to frequencies that are believed to have cancer-causing potential. Another mechanism that could help to explain the link between sunscreen use and increased risk of melanoma concerns vitamin D. This nutrient is made in the body as a result of the action of sunlight on the skin. Some studies show that sunscreen use may reduce vitamin D synthesis – a biochemical effect that may have important implications for health.

Vitamin D has a variety of functions in the body, one of which is to exert a broadly anti-cancer effect. This nutrient has the ability to dampen the uncontrolled cell growth that is the hallmark of cancer, and helps to induce suicide in cancerous cells. Interestingly, studies have found that vitamin D can inhibit malignant melanoma cells in the test tube. All this raises the question of whether the sub-optimal levels of vitamin D associated with sunscreen use may enhance the potential for melanoma. Indirect support for this idea has come other studies which show a link between reduced sunlight exposure and an increased risk of several other types of cancer including those of the colon, prostate and breast.

Evidence suggests that increasing vitamin D levels through sunlight exposure may do more than reduce our risk of cancer. One study, for instance, found that raised vitamin D levels induced by light exposure lowered blood pressure to an extent that would be expected to bring meaningful reductions in the risk of heart attacks and strokes. Vitamin D is essential for the strength and health of the bones and muscles too. While certain foods and supplements such as sardines, salmon and mackerel and cod liver oil can provide us with useful quantities of vitamin D, ensuring that our skin sees the light of day is the most effective way of maintaining optimal levels of this nutrient in the body.

While sunlight exposure does seem to have a range of health benefits, burning is to avoided as it is believed to age the skin prematurely and increase the risk of skin cancer too. Wearing appropriate clothing and taking to the shade when necessary are sensible precautions against sunburn. That said, it is clear that sunlight’s ability to boost vitamin D levels mean that its benefits are much more than skin deep.

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