Doubts over vitamin D supplements
Taking vitamin D supplements has little impact on health, according to a new review of trial evidence.
Researchers concluded that the capsules did not reduce the risk of heart attacks, strokes, cancers or bone fractures in the general population by more than 15%.
Previous studies have shown a strong link between vitamin D deficiency and poor health and early death.
But newer evidence suggests the association is chiefly due to low vitamin D being the result, not the cause, of ill health, it is claimed.
In the latest study based on 40 randomised trials, scientists used several types of meta-analysis - the pooling together of previous research data - to look at the benefits of vitamin D supplements.
This included a "futility" analysis predicting the potential of future results to sway existing evidence.
The researchers concluded that the effects of vitamin D supplementation on heart attack, stroke, cancer and bone fracture risk lay below a "futility threshold" - meaning further investigation would probably be pointless.
For hip fracture, some trials even suggested an increased risk from vitamin D supplements.
The scientists, led by Dr Mark Bolland from the University of Auckland in New Zealand, wrote in the medical journal The Lancet Diabetes and Endocrinology: " In view of our findings, there is little justification for prescribing vitamin D supplements to prevent myocardial infarction (heart attack) or ischaemic heart disease, stroke or cerebrovascular disease, cancer, or fractures, or to reduce the risk of death in unselected community-dwelling individuals.
"Investigators and funding bodies should consider the probable futility of undertaking similar trials of vitamin D to investigate any of these endpoints."
In a linked comment in the journal, Professor Karl Michaelsson, from Uppsala University in Sweden, pointed out: "Without stringent indications... there is a legitimate fear that vitamin D supplementation might actually cause net harm."
Dr Carrie Ruxton, from the Health Supplements Information Service, said: "In the light of the findings that 75% of the British population have below recommended intakes of vitamin D and that vitamin D is essential for bone health as well as a number of other physiological functions, consideration should be given to everyone taking a vitamin D supplement all year round."