Every man, woman and child over the age of five should consider taking vitamin D pills every year from October to March, according to Public Health England in a 2016 recommendation to "healthy bones, teeth and muscles receive". ,
The edict followed government-sponsored research by the Scientific Advisory Committee on Nutrition (SACN), which explores the links between vitamin D levels and musculoskeletal disorders, as well as a range of issues including heart disease, type 1 diabetes, cancer and multiple sclerosis were examined. One in five Britons suffered from low levels of so-called "sun vitamin" – which is essential, among other things, for healthy bones – said the committee.
Although small amounts of food, mainly oily fish, offal and eggs, can be obtained, vitamin D is actually a hormone produced primarily by the body in the skin in response to UV rays from the sun.
Small amounts of vitamin D can be found in foods such as fatty fish, offal and eggs. But it is actually a hormone that is mainly produced by the body
And the British weather, especially during the winter months, prevents a large proportion of the population from producing healthy amounts, the researchers said.
At the time, many doctors welcomed this "turnaround" in thinking and believed that this would contribute to the protection of public health. And, of course, the demand for dietary supplements jumped. Supermarket industry analyst The Grocer reports that sales jumped by a third, with British spending more than £ 7 million on vitamin D pills last year.
So a report earlier this month in the world-renowned medical journal The Lancet, which pointed out that vitamin D supplements did not improve bone strength, came as a surprise.
In fact, more than 30 new research papers have been published since the SACN study that question their findings. And there is growing concern in the scientific community with some who point out that the recommendations were little more than pseudoscience.
Worrying is also that reports of "overdoses" of dietary supplements appear: Vitamin D can accumulate in the body.
Rarely, high levels can lead to fatigue, muscle and joint pain, memory loss, painful kidney stones, and – paradoxically – to bone problems and broken bones.
Some researchers even demand that the guidelines for public health in England be reversed. How has vitamin D lost its shine?
WHO IS REALLY VITAMIN D DEFICIENT?
We all need vitamin D. Without this vitamin, we can not absorb calcium, which leads to bone loss and fracture risk.
Lack of it causes rickets in children and osteomalacia in adults, both of which are softening and weakening of bones with pain and malformations.
In children with rickets, vitamin D deficiency manifests as a characteristic bowing of the leg bones during growth.
Although descriptions of rickets first appeared in the Roman era, it was a particular scourge of the Victorian era, mainly due to the lack of sunlight in the smoggy industrial cities.
Public Health England has already asked people to take vitamin D supplements in the months of October and March
Cleaner air and better nutrition have almost wiped out the disease, but more cases have been reported, especially for children of Asian and African-Caribbean descent, who are at greater risk because their darker skin means they are not absorbing so much sunlight.
But there is a big difference between a clinical deficiency causing rickets or osteomalacia – in which blood levels of vitamin D are likely to be virtually undetectable – and "low levels of vitamin D" cited by SACN, which does not mean much anyway.
The amount of vitamin D in the body can be determined by a blood test. The chemical measured in the blood is called 25-hydroxy vitamin D, and the results are reported in units of nanomoles per liter (nmol / l).
The Department of Health defines low levels of vitamin D at a level of 25 nmol / l. This number was set about 20 years ago, at levels above which no risk of rickets could be identified.
However, this is not a diagnostic clinical threshold and this is never the case: falling below this level does not indicate illness or illness.
Doctors do not know how low or how long health problems need to be.
Public Health England recommends that we take 10 micrograms daily (in bottles as a microgram or microgram) of vitamin D supplementation in the winter. This dose was calculated to ensure that the vast majority of us achieve a blood level of 25 nmol / L. The current number falling below this level is about one in five.
How much do we actually need?
Just as there is no firm consensus about the deficiency, even less is known about what an optimal level could be. In America, a 2010 Institute of Medicine report found that a vitamin D level of 50 nmol or greater was "sufficient" for good bone health. Subsequently, a value below 50 was considered a vitamin D deficiency.
But in an article in the New England Journal of Medicine in 2013, several of the scientists who were in the original institute committee argued for a lower cut-off for vitamin D deficiency of 30 nmol / l.
The US Endocrine Society has gone the other direction and recommends very high blood levels – between 100 and 150 nmol / l – to guarantee "sufficiency".
Tim Spector (pictured), Professor of Genetic Epidemiology at King's College in London, believes that too many people are told that they need a vitamin D supplement
Tim Spector, Professor of Genetic Epidemiology at King's College in London, says that too many people are told that they need a vitamin D supplement, based on a fairly arbitrary assessment of what constitutes an appropriate level.
"At the population level, making cut-offs makes a big difference – just a small difference in numbers can mean that millions are being treated with a vitamin D deficiency, even though they do not actually have anything like that," says he.
"If your level is below 10 nmol / l, which is considered a clinical deficiency in most countries, this is fairly clear.You start to get vitamin D deficiency symptoms, so this would definitely be a reason, a supplement to to take.
"In my opinion, between 10 and 30 nmol / l is a gray area for suggesting dietary supplements, but you're probably okay with that, but most labs that offer tests suggest that blood levels above 60 or even 80 nmol are optimal Doctors then feel compelled to recommend supplements, and what is really important is whether these higher levels of real health outcomes – such as lower fracture rates – make a difference. "
In fact, the National Institute for Health and Care Excellence recommends that vitamin D blood tests should only be offered to patients with "deficiency symptoms or a very high risk". But they also find that tests have increased six-fold in recent years.
SO IT IS A BOOST FOR BONE … OR NOT?
In the most recent study on the effect of vitamin D on bone, researchers from Scotland and New Zealand collected data on 53,537 individuals from 81 randomized controlled trials, two-thirds of whom were over 65 years old.
The results provided reliable evidence that supplements – at doses above and below 20 micrograms per day – did not reduce the occurrence of fractures or falls.
In terms of blood levels of vitamin D, the study also found that below 50 nmol / L made no difference in the number of fractures or falls.
Recent research has shown that dietary supplements (pictured with fish oil capsules used as a dietary supplement with omega-3 and vitamin D supplements) did not reduce the occurrence of fractures or falls at doses above and below 20 micrograms per day
Co-author Professor Alison Avenell of Aberdeen's Health Services Research Unit says, "For many adults taking vitamin D supplements to increase bone density and prevent fractures and falls, our evidence shows that dietary supplements do not work. "
Professor Martin Hewison, Professor of Molecular Endocrinology, University of Birmingham: "Nutritional supplementation is only effective if you initially have vitamin D deficiency."
In short, a little vitamin D is needed to prevent your bones from decaying, but beyond that there is probably no other benefit.
What about all the other benefits?
There have been claims that vitamin D supplements can help from cancer to colds. But even the SACN report, which suggested improved bone health, found little evidence for any of the other suggested benefits.
In cancer, it noted that "the low number of available randomized clinical trials has not shown any effect of vitamin D supplementation on overall cancer risk."
It added that although higher vitamin D levels in the blood appear to be associated with a lower incidence of colorectal cancer, this does not provide compelling evidence of a protective effect of vitamin D, as other factors could be at work.
Vitamin D is a hormone produced primarily by the body in the skin in response to ultraviolet rays from the sun (Stock Image)
Similarly, the report found no significant effect of taking supplements for memory or depression.
Vitamin D levels tend to be lower among those with lower moods, but it is likely that depression can cause the problem – through behavioral changes like poor nutrition and staying indoors – and not the other way around.
Vitamin D is said to reduce the risk of cold and flu in a study published last year in the British Medical Journal. But Prof. Spector says, "To tell everyone that they should take vitamin D supplements would be more nonsense and pseudoscience.
"This study showed a tiny two percent difference in the absolute risk of a cold, and only those with low levels of vitamin D, who were probably sicker."
IF D IS REALLY DANGEROUS
There are no clear UK statistics on the doses of vitamin D that people take.
How should you get your daily dose?
In 2014, The Mail on Sunday columnist Dr. Michael Mosley and the University of Aberdeen found three ways for people with "low" vitamin D to increase their level.
They found that ten minutes of daily sun exposure at lunchtime, 25mcg (1000i.u.) Of vitamin D supplements and eating a 100g serving of oily fish three times a week were all similarly effective in increasing blood levels of vitamin D.
Correcting a severe deficiency, which is often part of a more complex set of health problems, could require much higher levels or vitamin D injections and should be discussed with your family doctor. Symptoms of vitamin D deficiency include lethargy, muscle aches, and bone pain.
Children aged one to four, house dwellers and people hiding for cultural / religious reasons should take 10mg of vitamin D throughout the year, adds Prof Avanell.
But for almost all of us, it's just necessary to stay out of the risk zone and get some sunshine and a good diet that should not be difficult, or high-dose supplements, says Prof Spector.
"If you're out in the sun in the summer and eat extra vitamin D sources like salmon, smoked herring, sardines and eggs, you might not need any supplements, and if you take one, there's less.
"According to the government's recommendations, a low-cost 10 mg daily dose, taken from October to March and available in most supermarkets, should be sufficient."
Over-the-counter supplements from supermarkets, health food stores and online come in everything from five to 100mcg cans.
Confusingly, supplements are sometimes also labeled in international units (i.u.).
One microgram of vitamin D equals 40i.u. Thus, a typical supplement can be labeled with 10 μg / μg or 400i.u.
A survey of US survey data released last year in the Journal of the American Medical Association found that the number of potentially unsafe levels – identified as more than 100mcg per day – increased 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 processed by the body and excreted in the urine.
"Vitamin D is fat-soluble and is eventually stored in the body where it can build up and be toxic," says Prof Spector.
In rare cases, vitamin D overload can lead to hypercalcaemia, which accumulates too much calcium in the blood and may form deposits in the arteries or soft tissues.
It happens because vitamin D stimulates the digestive tract to absorb more calcium. Acute symptoms can be thirst and confusion.
Ironically, more vitamin D may actually be worse than better for bones.
Prof. Spector says that the negative effects occur at around 20 mcg per day.
A 2010 study of women in Australia found that taking a vitamin D supplement equivalent to 34 mcg per day was associated with more falls and fractures.
Since this year, the supplements industry in the UK has set a voluntary upper limit of 75mcg for the amount of vitamin D sold, but 100mcg doses are still available online.
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