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Vitamin D supplements do nothing for bone health and the government should give up its view that everyone should take it during the winter months, according to the authors of the largest review of evidence ever made.
The results challenge the established vision of vitamin D and dismay many people who believe that a daily dose of this vitamin is good for them. But the big meta-analysis, which brought together 81 separate studies to come up with the strongest possible conclusions, found that there was no reason to take vitamin D supplements for bone health, with the exception of those with a high risk of developing some rare diseases. .
The Ministry of Health is currently saying that everyone should consider taking a vitamin D supplement for the health of their bones during the winter months, from October to March, if they can not have enough with sun exposure. This includes all infants and children from six months to five years old. It is based on the findings of the Government's Scientific Advisory Committee on Nutrition (SACN) in July 2016, which concluded that there are no other health benefits.
The new meta-analysis is published in the journal Lancet Diabetes and Endocrinology and is led by long-time vitamin D experts, Professors Mark Bolland and Andrew Gray, of the University of Auckland, New Zealand, and by Professor Alison Avenell from Aberdeen University.
Bolland said things had changed since 2014, the year of the last major review of evidence. In the past four years, "more than 30 randomized controlled trials of vitamin D and bone health have been published, doubling the amount of evidence available," he said.
"Our meta-analysis revealed that vitamin D does not prevent fractures, falls, or the improvement of bone mineral density, either at high or low doses."
He added that advice given by doctors and health departments around the world recommending vitamin D and stating that it was helpful in osteoporosis or fragile bone disease, which affects older people, should now be changed. "The clinical guidelines need to be changed to reflect these results," he said.
He added that new tests on the effects of vitamin D on bone health would be useless. "On the basis of existing evidence, we believe that there is little justification for increasing vitamin D supplement trials on musculoskeletal outcomes," he said.
Everyone needs vitamin D; the question is whether we should get it from supplements. It is made naturally in the body as a result of sun exposure. That's why people living in northern climates and those who cover their skin may have lower levels than they should. It is also contained in a small number of foods, such as cod liver oil, organ meats, egg yolk and oily fish, including salmon and mackerel.
The studies that have been done primarily concern the elderly who may be at risk for osteoporosis (brittle bones), but Avenell said that there was no evidence of benefits for adults – with the exception of those who are at high risk of osteomalacia, a form of rickets in adults.
"I think they should change direction," she said. "We do not believe that the population should take vitamin D supplements, because clinical trials have shown no benefit in terms of protection against falls and fractures, or against all that vitamin D is supposed to protect you from.
"There is no harm in taking low-dose vitamin D supplements as far as we know, but if [the government’s nutrition advisers] really convinced that this has important effects, they should surely recommend the fortification of foods. "
They did not talk about the effects of supplements on children and young people, she said, because there was no trial. They also made it very clear that people who were not exposed to the sun because they were covered or institutionalized risked vitamin D deficiency.
"The background to this analysis is that many patients (and doctors) have been persuaded by various studies and social media that Vitamin D is a panacea," said J Chris Gallagher of the Medical Center. Creighton University in Omaha, United States. , in a comment linked in the newspaper.
"This reflection is reminiscent of the fervor that drove the widespread use of Vitamin A, Vitamin C and Vitamin E many years ago, and all of these vitamin trials were clinically negative later.
"The authors should be complimented for an important updated analysis on musculoskeletal health, but I can already hear the strong supporters. What about the extra-skeletal benefits of vitamin D?
According to the SACN, it has been suggested that vitamin D may help solve a number of other "extra-skeletal" health problems, including cancer, heart disease, high blood pressure, diseases infectious diseases, neuropsychological functioning, oral health and age-related macularity. degeneration, although found no convincing evidence for any of these. Gallagher thinks current studies will answer these questions.
"We may have this answer within three years because about 100,000 participants are currently enrolled in randomized, placebo-controlled trials of vitamin D supplementation," he wrote. "I'm looking forward to seeing these studies give us the last word on vitamin D."
Professor Louis Levy, head of nutrition science at Public Health England, said people should continue to take supplements. "With one-fifth of Britons showing vitamin D levels, the government is recommending it through the sun and a healthy, balanced diet in summer and spring," he said. "In autumn and winter, those who do not consume foods naturally containing or fortified with vitamin D should consider an extra 10 micrograms."
Martin Hewison, professor of molecular endocrinology at the University of Birmingham, confirmed this view, adding that many vitamin D supplementation trials have shown that it is effective only if people are deficient in vitamin D, but that in this study, very few participants started with low levels of vitamin D.
"What the current study illustrates," he said, "is that more studies are needed to target vitamin D supplementation where it is needed – in people with vitamin D deficiency. vitamin D".
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