Vitamin D supplements do nothing for bone health, according to the authors of the biggest review of the evidence ever carried out.
The findings challenge the established view of vitamin D and will dismay the many people who believe a daily dose of it is doing them good.
But the large meta-analysis, the authors of which compiled 81 separate studies to come to the most robust possible conclusions, found there was no evidence to justify taking vitamin D supplements for bone health, except for those at high risk of a few rare conditions.
The new meta-analysis is published in the Lancet Diabetes & Endocrinology journal and led by the longstanding experts on vitamin D, Professors Mark Bolland and Andrew Grey from the University of Auckland in New Zealand, and Professor Alison Avenell of Aberdeen University.
Prof Bolland said things have changed since 2014, when the last major review of the evidence was carried out. In the last four years, "more than 30 randomised controlled trials on vitamin D and bone health have been published, nearly doubling the evidence base available", he added.
"Our meta-analysis finds that vitamin D does not prevent fractures, falls or improve bone mineral density, whether at high or low dose."
Prof Bolland said the advice given by doctors and government health departments around the world recommending vitamin D and saying it is helpful in osteoporosis or brittle bone disease, which afflicts older people, should now be altered. "Clinical guidelines should be changed to reflect these findings."
Professor Mark Bolland said the advice given by doctors and government health departments around the world recommending vitamin D and saying it is helpful in osteoporosis or brittle bone disease, which afflicts older people, should now be altered.
He added that further trials looking at the effects of vitamin D on bone health would be pointless. "On the strength of existing evidence, we believe there is little justification for more trials of vitamin D supplements looking at musculoskeletal outcomes."
Everybody needs vitamin D; the question is whether we should get it from supplements.
It is made in the body naturally as a result of exposure to sunlight, which is why people living in northern climates and those who cover up their skin may have lower levels than they should.
It is also contained in a small number of foods, such as cod liver oil, offal, egg yolk and oily fish, including salmon and mackerel.
The studies that have been done are mostly on older people who could be at risk of osteoporosis (brittle bone disease), but Prof Avenell said there is no evidence of benefit for any adults - apart from those few who are at high risk of osteomalacia, a form of rickets in adults.
"We don't think that the population needs to take vitamin D supplementation, because trials don't show it has any benefit in protecting against falls and fractures, or all the other things vitamin D is supposed to protect you against.
"There's no harm in taking low-dose vitamin D supplements as far as we know, but if (the government's nutrition advisers) really believed it has important effects, surely they should be recommending that there should be fortification of food."
They were not talking about the effects of supplements in children and young people, she said, because there had not been trials.
They were also very clear, Prof Avenell said, that people who were never exposed to the sun because they covered themselves up or were institutionalised were at risk of vitamin D deficiency.
"The context for this analysis lies in the fact that many patients (and doctors) have been persuaded by various studies and social media that vitamin D is a cure-all," said Professor J. Chris Gallagher of the Creighton University Medical Centre in Omaha in the United States, in a linked comment in the journal.
"This thinking is reminiscent of the fervour that supported the widespread use of vitamin A, vitamin C and vitamin E years ago, and all of those vitamin trials later proved to be clinically negative."