LONDON 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. 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. Prof Autier said: "What this discrepancy suggests is that decreases in vitamin D levels are a marker of deteriorating health. 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. "And we already know that people who are at risk of vitamin D deficiency, like older people, pregnant and breastfeeding women, young children and people with darker skin, need to take a supplement because it is difficult to boost vitamin D levels from food sources alone," she said. "It has been known for almost a century that vitamin D supplements given to those with deficient vitamin D levels results in improved bone health, preventing hypocalcemic seizure and rickets." Helen Macdonald, a professor of nutrition and musculoskeletal health at Britain's University of Aberdeen stressed that vitamin D was important for bone health.
– Is there any point in healthy people taking vitamin D supplements? New research suggests that while low levels of the "sunshine vitamin" are linked to many illnesses, the deficiency is a result, not a cause of sickness, reports Reuters. French researchers who reviewed hundreds of other studies were unable to find any link between taking vitamin D supplements and having a reduced risk of contracting illnesses including cancer, diabetes, and cardiovascular disease. The review suggests "decreases in vitamin D levels are a marker of deteriorating health," the lead researcher says. Experts not involved in the study say that while it shows that more long-term studies of the vitamin's effects are needed, it shouldn't be a reason for people ceasing to take supplements—especially among groups at risk of deficiency, including older people, pregnant and breastfeeding women, young children, and people with darker skin. The French study also failed to look at bone health, critics note. "It has been known for almost a century that vitamin D supplements given to those with deficient vitamin D levels results in improved bone health, preventing hypocalcemic seizure and rickets," a leading pediatrician tells the BBC.