Why do scientists say that the government is totally recommending vitamin D this winter?

All men, women and children over the age of five should consider taking vitamin D tablets from October to March, year by year, according to the recommendations of Public Health England, in their 2016 recommendation, in order to " contribute to healthy bones, teeth and muscles. .

This order was a follow-up to a government-sponsored Scientific Advisory Committee on Nutrition (SACN) study that examined the links between vitamin D levels and musculoskeletal health, as well as a range of issues. including heart disease, type 1 diabetes, cancer and multiple sclerosis. . One in five Britons suffered from low levels of "sun vitamin", which is essential for healthy bones, among other things, the committee said.

Although small amounts can be obtained from foods, mainly oily fish, organ meats and eggs, vitamin D is actually a hormone, mainly produced by the body, in the skin, in response to UV rays of the sun.

And British weather, especially during the winter months, is preventing much of the population from generating healthy amounts, the researchers said.

At the time, many doctors welcomed this "radical change" in their thinking, believing that it would help protect public health. And not surprisingly, the demand for supplements has risen sharply. According to The Grocer, an analyst in the mass-market sector, sales jumped by a third, with the British spending more than £ 7m on vitamin D tablets last year.

For example, an article published earlier this month in the world-renowned medical journal The Lancet that vitamin D supplements did not improve bone strength was a surprise.

In fact, more than 30 new research papers have been published since the SACN study, questioning their findings. And the scientific community is increasingly worried, with some suggesting that the recommendations are little more than pseudo-science.

More worryingly, cases of "overdose" supplements have begun to emerge: vitamin D can accumulate in the body.

Although rare, high levels can lead to fatigue, muscle and joint pain, memory loss, painful kidney stones and – paradoxically – a risk of bone problems and fractures.

Some researchers even ask that the guidelines of Public Health England be reversed. So, how did vitamin D lose its luster?

WHO HAS REALLY VITAMIN D?

We all need vitamin D. Without it, we can not absorb calcium, resulting in thinning bones and a risk of fracture.

A deficiency causes rickets in children and osteomalacia in adults, which are a softening and weakening of bones with pain and deformities.

In children with rickets, vitamin D deficiency manifests as a characteristic sagging of leg bones as they grow.

Although descriptions of rickets first appeared in the Roman era, it was a particular scourge of the Victorian era, largely because of the lack of sunshine in industrial cities overrun by smog.

Cleaner air and better nutrition have virtually eradicated the disease, but cases have been reported again, mainly in children of Asian and Afro-Caribbean origin who are at greater risk because their darker skin prevents from absorbing as much sunlight.

But there is a big difference between a clinical deficiency causing rickets or osteomalacia – for which blood levels of vitamin D are likely to be virtually undetectable – and the "low vitamin D content" cited by the SACN, which can anyway do not cause much concern.

Vitamin D levels in the body can be determined via a blood test. The chemical measured in the blood is called 25-hydroxyvitamin D and the results are reported in nanomoles per liter (nmol / l).

The Ministry of Health defines a low vitamin D content as having a level of 25 nmol / l. This figure was fixed about 20 years ago, at a level above which no risk of rickets could be identified.

However, this is not and has never been a clinical diagnostic threshold: a low below this score does not indicate a disease or a disease.

Doctors do not know how much to be low or how long to cause health problems.

Public Health England recommends taking a daily vitamin D supplement of 10 micrograms (indicated on vials as μg or mcg) in winter. This dose was calculated so that the vast majority of us reach a blood level of 25 nmol / l. The current number of people falling below this level is about one in five.

WHAT DO WE NEED REALLY?

Just as there is no firm consensus on deficiencies, so much less is known about what might be an optimal level. In America, a report from the Institute of Medicine in 2010 stated that a level of vitamin D equal to or greater than 50 nmol was "enough" for good bone health. Subsequently, a level below 50 was considered vitamin D deficiency.

However, in a 2013 article in the New England Journal of Medicine, several of the scientists who were part of the Institute's original committee argued for a reduction in vitamin D deficiency of 30 nmol / l.

The Endocrine Society of the United States has done the opposite and recommends very high blood levels – between 100 and 150 nmol / l – "to ensure sufficiency".

Tim Spector, professor of genetic epidemiology at King's College London, explains that too many people are told that they need a vitamin D supplement, based on a rather arbitrary assessment of what constitutes an adequate level.

"At the population level, it is very difficult to define thresholds. Only a small difference in numbers can mean that millions of people are being treated with vitamin D deficiency when they have nothing like it, "he says.

"If your level is below 10 nmol / l, generally accepted as a clinical deficit in most countries, it's pretty clear.You start to have symptoms of vitamin D deficiency, so that would certainly be a reason to take a supplement .

"In my opinion, between 10 and 30 nmol / l is a gray area indicating if you offer supplements.Above you are probably well.But most laboratories offering tests suggest blood levels over 60 or even 80 As a result, physicians feel obligated to recommend supplements, and what really matters is that these higher levels make a difference in actual health outcomes – such as lower fracture rates – and they do not do it.

In fact, the National Institute for Excellence in Health and Care recommends that blood tests for vitamin D be offered only to patients with "deficiency or very high risk symptoms". But they also note that the tests have been multiplied by six in recent years.

IS THIS IF IT IS AN OVERVIEW FOR BONE … OR NOT?

In the latest study on the effects of vitamin D on bone, Scottish and New Zealand researchers collected data on 53,537 people in 81 randomized controlled trials, two-thirds of which involved people over the age of 65 years.

The results revealed reliable evidence that supplements – at doses greater than or less than 20 mg per day – did not reduce the incidence of fractures or falls.

In terms of blood levels of vitamin D, the study also showed that less than 50 nmol / l made no difference to the number of fractures or falls.

Associate Professor Alison Avenell of the Health Services Research Unit at Aberdeen University said, "For many adults taking vitamin D supplements to increase bone density and prevent fractures and falls, our evidence shows that supplements do not work. "

According to Professor Martin Hewison, a professor of molecular endocrinology at the University of Birmingham: "Supplementation is only effective if you are deficient in vitamin D".

In short, a little vitamin D is needed to prevent the crumbling of your bones, but beyond that, there is probably no other benefit.

WHAT IS IT FOR ALL OTHER BENEFITS?

Some have argued that vitamin D supplements can help anything from cancer to colds. However, even the SACN report, which suggested an improvement in bone health, indicated that there was little evidence of any of the other benefits suggested.

On cancer, he said that "the small number of randomized clinical trials available has not shown any effect of vitamin D supplementation on overall cancer risk."

He added that, although high levels of vitamin D in the blood appear to be associated with a lower incidence of colorectal cancer, this does not constitute convincing evidence of a protective effect of vitamin D, d 39 other factors that may be at the origin of the work.

Likewise, the report did not reveal any significant effect of taking supplements on memory or depression.

Vitamin D levels tend to be lower in moody people, but it's likely that being depressed can pose the problem – through behavioral changes such as a bad one feeding and staying indoors – rather than the opposite.

In a study published last year in the British Medical Journal, vitamin D would reduce the risk of colds and flu. But Professor Spector said: "To tell everyone to take vitamin D supplements as a result of this operation would be more absurd and pseudo-scientific.

"This study showed a minimal difference of 2% in the absolute risk of colds, and only in those with low vitamin D levels who were probably sicker."

WHEN D REALLY DANGER

In the United Kingdom there are no clear statistics on the doses of vitamin D that people take.

Over-the-counter supplements in supermarkets, health food stores and online are available in doses ranging from 5 to 100 μg.

In a confusing way, the supplements are sometimes also labeled in international units (i.u.).

One microgram of vitamin D equals 40 i.u. a typical supplement may be labeled 10 mcg / μg or 400 i.u.

A review of US national survey data released last year in the Journal of the American Medical Association revealed that the number of people taking potentially harmful doses – identified as being greater than 100 mg / day – went from virtually zero to more than three percent between the first survey in 2000 and the last survey in 2014.

The problem is that, unlike water-soluble vitamins such as vitamins C and B, excess amounts are not treated by the body and are excreted in the urine.

"Vitamin D is fat soluble and ends up being stored in the body, where levels can accumulate and become toxic," says Professor Spector.

In rare cases, vitamin D overload can lead to hypercalcemia, a condition characterized by excessive accumulation of calcium in the blood that can form deposits in the arteries or soft tissues.

This happens because vitamin D stimulates the digestive tract to absorb more calcium. Acute symptoms can include thirst and confusion.

Ironically, more vitamin D can also be worse than good for bones.

According to Professor Spector, the negative effects are around 20 μg per day.

A 2010 study of Australian women found that taking a vitamin D supplement equivalent to 34 mg daily was associated with more falls and fractures.

As of this year, the supplement industry in the UK has set a voluntary limit of 75 mg for the vitamin D dose sold, but 100 mg doses are still available online.

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