Vitamin D supplements probably provide little, if any, health benefits, a New Zealand study has concluded.
Previous observational studies have claimed that vitamin D deficiency is strongly linked to poor health and early death.
But subsequent evidence from randomised controlled trials has suggested that the link is not causal, which means taking supplements are unlikely to yield any health benefits.
And results of a large systematic review by Philippe Autier and colleagues, published in The Lancet and The Lancet Diabetes & Endocrinology in December 2013 also suggested that low levels of vitamin D are a consequence, not a cause, of ill health.
Dr Mark Bolland, senior research fellow at the University of Auckland’s School of Medicine and colleagues, have built on this using several types of meta-analysis, including a “futility analysis”, which predicts the potential of future study results to sway existing evidence.
They examined evidence from 40 randomised controlled trials and the results of his study, published in The Lancet Diabetes & Endocrinology, has indicated that the effect of vitamin D, taken with or without calcium, on heart attack, stroke, cancer, and total fracture, lies below a “futility threshold”.
For hip fracture, the results of some trials actually suggested there was an increased risk with vitamin D supplementation.
Analysis as to whether or not vitamin D supplements can reduce mortality by 5% or more was inconclusive.
Bolland M, Grey A et al. The effect of vitamin D supplementation on skeletal, vascular, or cancer outcomes: a trial sequential meta-analysis. The Lancet. 24 January, 2014. http://dx.doi.org/10.1016/S2213-8587(13)70212-2 [abstract]
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