Friday, December 06, 2013

Study casts doubt on whether extra vitamin D prevents disease

Study casts doubt on whether extra vitamin D prevents disease By Kate Kelland LONDON (Reuters) - Researchers cast doubt on the prevailing wisdom that vitamin D supplements can prevent conditions like cancer, diabetes and heart disease, saying on Friday low vitamin D may be a consequence, not a cause, of ill health. The findings could have implications for millions of people who take vitamin D pills and other supplements to ward off illness - Americans spend an estimated $600 million a year on them alone. Vitamin D, sometimes known as the "sunshine vitamin" is made in the body when the skin is exposed to sunlight and in found in foods like fish liver oil, eggs and fatty fish such as salmon, herring and mackerel. [...] Researchers led by Philippe Autier of France's International Prevention Research Institute in Lyon analyzed data from several hundred observational studies and clinical trials examining the effects of vitamin D levels on so-called non-bone health - including links to illness such as cancer, diabetes and cardiovascular disease. They found that the benefits of high vitamin D levels seen in observational studies — including reduced risk of cardiovascular events, diabetes and colorectal cancer - were not replicated in randomized trials where participants were given vitamin D to see if it would protect against illness. "What this discrepancy suggests is that decreases in vitamin D levels are a marker of deteriorating health," said Autier. In other words, he explained, serious illness like cancer and diabetes may reduce vitamin D concentrations, but that does not necessarily mean that raising vitamin D levels would prevent the illness from occurring.

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