Scientists have cast doubt on the value of vitamin D supplements to protect against diseases such as cancers, diabetes and dementia.
Writing in The Lancet Diabetes and Endocrinology, French researchers suggest low vitamin D levels do not cause ill health, although they did not look at bone diseases. More clinical trials on non-skeletal diseases are needed, they say.
Vitamin D supplements are recommended for certain groups. Recent evidence has shown it may also have a role to play in preventing non-bone-related diseases such as Parkinson's, dementia, cancers and inflammatory diseases.
Prof Philippe Autier, from the International Prevention Research Institute in Lyon, carried out a review of data from 290 prospective observational studies and 172 randomised trials looking at the effects of vitamin D levels on health outcomes, excluding bone health, up to December 2012.