Tue, Feb 17, 2009 - Page 16 News List

Sunshine, both good and bad

If you stay in the sun you run the risk of skin cancer; if you avoid the sun you end up with vitamin D deficiency and rickets. So just how much sunlight is safe for us?



For any expectant mother, a brief stroll in the summer sunshine would seem a pleasant diversion from the rigors of pregnancy, a chance to relax in the warmth and to take in a little fresh air. It is a harmless — but unimportant — activity, it would seem.

But there is more to such walks than was previously realized, it emerged last week. In a new study, researchers at Bristol University revealed they had found out that sunny strolls have striking, long-lasting effects. They discovered that children born to women in late summer or in early autumn are, on average, about 5mm taller, and have thicker bones, than those born in late winter and early spring.

Nor was it hard to see the causal link, said team leader Jon Tobias. The growth of our bones, even in the womb, depends on vitamin D, which, in turn, is manufactured in the skin when sunlight falls on it.

Thus children born after their mothers have enjoyed a summer of sunny walks will have been exposed to more vitamin D and will have stronger bones than those born in winter or early spring. “Wider bones are thought to be stronger and less prone to breaking as a result of osteoporosis in later life, so anything that affects early bone development is significant,” said Tobias.

The study is important, for it indicates that women should consider taking vitamin D supplements during pregnancy to ensure their children reach full stature. However, the team’s findings go beyond this straightforward conclusion, it should be noted. Their work adds critical support to a controversial health campaign that suggests most British people are being starved of sunshine, and vitamin D — a process that is putting their lives at risk.

These campaigners point to a series of studies, based mainly on epidemiological evidence, that have recently linked vitamin D deficiency to illnesses such as diabetes, breast cancer, prostate cancer and tuberculosis. Last week also saw George Ebers, professor of clinical neurology at Oxford University, unveil evidence to suggest such a deficiency during pregnancy and childhood could increase the risk that a child would develop multiple sclerosis.

The studies require rigorous follow-up research, scientists admit — but they have nevertheless provoked considerable new interest in vitamin D. Indeed, for some health experts, the substance has virtually become a panacea for all human ills. Dietary supplements should be encouraged for the elderly, the young and the sick, while skin cancer awareness programs that urge caution over sunbathing should be scrapped, they insist. We need to bring a lot more sunshine into our lives, it is claimed.

But this unbridled enthusiasm has gone down badly with health officials concerned about soaring rates of melanomas in Britain, the result of over-enthusiastic suntanning by holidaymakers decades ago. Existing, restrictive recommendations for limits on sunbathing must be rigorously maintained, they argue, or melanoma death rates will rise even further.

So just how much sunlight is safe for us? And which is the greater risk: skin cancer or diseases triggered by vitamin D deficiency? Answers for these questions now cause major divisions among health experts.

In fact, vitamin D is not strictly a vitamin. Vitamins are defined as nutrients that can only be obtained from the food we eat and which are vital to our health. For example, vitamin C, which wards off scurvy and helps the growth of cartilage, is found in citrus fruits, while broccoli and spinach are rich in vitamin K, which plays an important role in preventing our blood from clotting. And while it is true that vitamin D is found in oily fish, cod liver oil, eggs and butter, our principal source is sunlight.

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