Many people buy and take Vitamin D supplements for its supposed health benefits as they have been widely promoted as a tool for fighting a range of unwanted health conditions that include autoimmune disorders, osteoporosis and heart disease.

What made marketing of vitamin D supplements effective is that many of the supposed benefits of taking Vitamin D supplements are based on studies. Unfortunately, the real benefits of vitamin D intake still remain unclear if not controversial.

A new study published in the British Medical Journal on April 1 adds to a growing number of studies that question the real benefits of vitamin D. In the research "Vitamin D and multiple health outcomes: umbrella review of systematic reviews and meta-analyses of observational studies and randomised trials", Evropi Theodoratou of the Centre for Population Health Sciences at the University of Edinburgh in U.K and colleagues reviewed more than 260 earlier studies which include clinical trials and observational studies on the potential health benefits of Vitamin D when consumed from natural sources and taken as a supplement.

The researchers found that of the 137 health benefits associated with vitamin D, only 10 were based on what they consider as rigorous trials and only one study which links a child's birth weight to the vitamin D levels of the mother during the third trimester of pregnancy showed evidence of Vitamin D benefit which means that there are hardly evidence to establish Vitamin D's role in the outcomes.

"Despite a few hundred systematic reviews and meta-analyses, highly convincing evidence of a clear role of vitamin D does not exist for any outcome, but associations with a selection of outcomes are probable," the researchers reported.

The researchers said there may be a link between vitamin D levels and tooth decay in children, birth weight, parathyroid hormone levels in patients with chronic kidney disease that require dialysis and maternal vitamin D concentrations at term but these associations still need to be proven through further studies.

A growing number of studies have already questioned many of the health benefits associated with Vitamin D supplements. A study published on bone density published in the Lancet Medical Journal in January found that vitamin D supplement alone is not sufficient in preventing fractures.