Vitamin D not needed for healthy people, study finds
There is little reason to prescribe vitamin D supplements to healthy adults to reduce the risk of diseases or fractures, say researchers writing in the Lancet.
They found no significant reduction in risk in any area after analysing more than 100 trials.
They added that future studies were unlikely to change the figures.
At-risk groups, including babies, pregnant women and elderly people, are still advised to take supplements.
The research team, from the University of Auckland in New Zealand, had previously carried out a meta-analysis which showed no major effect of vitamin D supplementation on bone mineral density.
In this study, they looked at existing randomised controlled trials of vitamin D supplements, with or without calcium.
They found that vitamin D supplementation does not change the relative risk of heart disease, stroke or cerebrovascular disease, cancer and fractures by a noticeable amount, equivalent to 15%.
Vitamin D supplements did not reduce hip fracture risk by more than 15% in hospital patients and, when given with calcium, did not lessen the risk in healthy individuals either.
The study said there was also "uncertainty as to whether vitamin D with or without calcium reduces the risk of death".
The New Zealand researchers concluded: "In view of our findings, there is little justification for prescribing vitamin D supplements to prevent myocardial infarction or ischaemic heart disease, stroke or cerebrovascular disease, cancer, or fractures, or to reduce the risk of death in unselected community-dwelling individuals."
'Far from clear'
Writing in a linked article in the Lancet, Karl Michaelsson, from the department of surgical sciences at Uppsala University in Sweden, said there was continuing debate about whether there were health benefits to taking vitamin D supplements for a mild form of vitamin D deficiency.
"The impression that vitamin D is a sunshine vitamin and that increasing doses lead to improved health is far from clear."
Mr Michaelsson said that until more information was available, it would be wise to choose a cautious approach to vitamin D supplementation for otherwise healthy individuals.
While some nutrition experts say vitamin D deficiency is responsible for a number of diseases, such as fractures, cancer, cardiovascular diseases, diabetes, and a higher risk of death, others say vitamin D deficiency is more likely to be the result of ill health and not the cause.
Dr Colin Michie, consultant senior lecturer in paediatrics and chairman of the nutrition committee at the Royal College of Paediatrics and Child Health, says the study puts Vitamin D supplements into context.
"This shows vitamin D has a relevant role to play, but it's not that important.
"GPs shouldn't be rushing around getting blood tests done for the average healthy person.
"Instead, the old-fashioned advice still holds true. Eat more fish, watch your diet and how you lead your life - unless you're specifically at risk."
People at high risk of vitamin D deficiency include children under five, pregnant and breastfeeding women, the over-65s and people at risk of not getting enough exposure to sunlight.
Those with darker skin, such as people of African, Caribbean and South Asian origin, and people who wear full-body coverings, as well as pale-skinned people have also been shown to be at higher risk.