Trials of vitamin D have little chance of showing health benefits

28 January 2014

Heart attack, stroke, cancer or bone fractures are not significantly prevented by the use of vitamin D supplements, according to a recent study.

The new study concludes that evidence is lacking for any substantial health benefits of vitamin D and that the results from several multimillion-dollar trials underway are unlikely to alter this view.

The study, led by Dr Mark Bolland from the University of Auckland, was published this week in UK medical journal, The Lancet Diabetes & Endocrinology.

It examines existing evidence from 40 randomised controlled trials and concludes that vitamin D supplementation does not prevent heart attack, stroke, cancer, or bone fractures in the general population by more than 15 percent.

“Vitamin D supplements, (that are taken by nearly half of all adults in the United States), probably provide little, if any, health benefit,” says Dr Bolland.

Previous observational studies showed that vitamin D deficiency was strongly associated with poor health and early death. The evidence from randomised controlled trials now indicates that this association is not causal i.e. that supplementation is not likely to have any benefit.

In line with this idea, the results of a large systematic review by Philippe Autier and colleagues, published in December 2013, also in The Lancet Diabetes & Endocrinology, suggested that low levels of vitamin D are a consequence, not a cause, of ill health.

“This evidence from the randomised controlled trials now indicates that this association is not causal – that is, that supplementation is not likely to have any benefit,” says Dr Bolland.

In the new study, Dr Bolland and colleagues built on this evidence using several types of meta-analysis, including a ‘futility analysis’ that predicts the potential of future study results to sway existing evidence.

The results of their study indicate that the effect of vitamin D, taken with or without calcium, on heart attack, stroke, cancer, and total fracture lies below a ‘futility threshold’ of 15 per cent.

For hip fracture, the results of some trials even suggested increased risk with vitamin D supplementation. The authors’ analysis of whether vitamin D supplementation can reduce mortality by five per cent or more was inconclusive.

For more information contact:

Suzi Phillips , Media Relations Advisor Faculty of Medical and Health Sciences The University of Auckland Email Phone +64 9 923 7383 or Mob 021416396