Washington: Researchers have cast doubt on vitamin D's ability to offer us protection against diseases like cancer, diabetes and dementia.
According to French researchers, low vitamin D levels don't cause ill health.
Recent evidence has come to light that shows that it may play a part in preventing non-bone-related diseases like Parkinson's, dementia, cancers and inflammatory diseases.
Prof Philippe Autier, from the International Prevention Research Institute in Lyon, carried out a survey of information from 290 prospective observational studies and 172 randomised trials that looked at the effects of vitamin D levels on health outcomes, excluding bone health, up to December 2012.
A large number of the observational studies have suggested that there were benefits from high vitamin D - and that it could cut cardiovascular disease risk by up to 58 per cent, diabetes by up to 38 per cent and colorectal cancer by up to 33 per cent.
However, the results of the clinical trials - where vitamin D supplements were given to the participants - found no reduction in risk, even among people who started out with low vitamin D levels.
A further analysis of recent randomised trials found that there was no positive effect of vitamin D supplements on diseases occurring.
The study has been published in The Lancet Diabetes and Endocrinology.