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There is ‘not enough evidence’ that taking vitamin D can prevent or treat Covid-19, according to a UK Government review.
But officials are still recommending Britons take the immune-boosting nutrient over the winter.
Health Secretary Matt Hancock ordered a rapid review into the vitamin’s effect on Covid in October, after coming under fire for writing it off without any evidence to back his claims.
A panel of experts across multiple Government agencies, including Public Health England, analysed ‘the best’ scientific studies from around the world, though they did not say which or how many papers they looked at.
But the team, led by NHS watchdog NICE, said ‘it was not possible’ to determine a direct relationship between vitamin D and Covid, citing a lack of high-quality trials.
A mountain of studies have found that an overwhelming amount of people who get Covid-19 do not have enough vitamin D in their bodies and the sickest of patients are often deficient.
But scientists have so far been unable to pin down whether the deficiency makes people more vulnerable to Covid, or whether becoming unwell causes vitamin D levels to crash.
NICE is still urging Britons to supplement 10 micrograms (400 IU) of vitamin D every day between October and early March because of its other proven health benefits on bones, muscles and the immune system.
Experts believe people may not have been making enough vitamin D from sunlight this year due to prolonged periods indoors as a result of the pandemic.
Vitamin D supplements are safe, cheap and readily available. They cost as little as 6p a pill and are sold in most pharmacies, supermarkets and health shops.
There is ‘not enough evidence’ that taking vitamin D supplements can prevent or treat coronavirus, according to a UK Government review (stock image)
One study found that 72 per cent of NHS workers in Birmingham who were lacking in the ‘sunshine vitamin’ (left column) tested positive for coronavirus antibodies in the blood — a sign of previous infection. This compared to just 51 per cent for those who had a healthy amount of the vitamin (right column)
Dr Paul Chrisp, director of the centre for guidelines at NICE, said: ‘While there is insufficient evidence to recommend vitamin D for the prevention or treatment of Covid-19 at this time, we encourage people to follow Government advice on taking the supplement throughout the autumn and winter period.
‘As research continues on the impact of vitamin D on Covid-19, we are continuing to monitor evidence as it is published and will review and update the guidance if necessary.’
Elderly Brits and people with dark skin are advised to take vitamin D year-round because they are more likely to be deficient than other groups.
Older people tend to spend less time outdoors so have less exposure to the sunshine. The body produces vitamin D naturally when exposed to the sun.
Black and ethnic minority people (BAME) are more likely to be deficient because it is harder for darker skin types to absorb the nutrient from sunlight.
More than 2.5million vulnerable people across England have been offered free vitamin D supplements this winter.
Professor Ian Young, chairman of the Scientific Advisory Committee on Nutrition, who was involved in the review, said: ‘This evidence review confirms that currently there is not enough available evidence to determine that there is a causal relationship between vitamin D and Covid-19.’
Dr Alison Tedstone, chief nutritionist at Public Health England, said: ‘Vitamin D is important for our bone and muscle health.
‘We advise that everyone, particularly the elderly, those who don’t get outside and those with dark skin, takes a vitamin D supplement containing 10 micrograms (400 IU) every day.
‘This year, the advice is more important than ever with more people spending more time inside.’
Researchers from Queen Mary University of London are currently carrying out a randomised trial probing the potential benefits of the nutrient on Covid-19.
The scientists gave 5,000 volunteers the vitamin in October and will assess them over six months if they do not already take high doses.
Experts will then assess whether participants are at less risk of catching the virus and developing a severe bout of the disease over the winter months.
Britons are most at risk of being vitamin D deficient between October and April when sunlight levels are too low for the body to make the vitamin.
Around two in five Brits are deficient during the winter, when respiratory infections are most common. In the US, at least two in five citizens also lack sufficient levels of the vitamin.
The current advice from Public Health England and the NHS is for everybody to consider taking a daily supplement of 10 micrograms – the amount found in one small salmon fillet – during the winter months when sun is hard to come by.
The NHS says the general consensus is levels of below 25nmol/L — the equivalent of 10ng/ml — in the blood indicate vitamin D deficiency.
This is thought to be the equivalent of taking around 10 micrograms of vitamin D a day.
Arguments on the link between vitamin D deficiency and its observed link with poor Covid-19 outcomes started to gather pace as early as May.
The problem lies in the fact there is a lack of gold-standard medical research — the randomised controlled trials which compare people who are given the supplement with those who are not to see which group fares better.
Only one study has done this so far, conducted by the University of Cordoba in Spain and published earlier in the autumn.
Researchers gave high doses of calcifediol – a type of vitamin D supplement – to 50 patients hospitalised with the disease.
There were no deaths among volunteers receiving the vitamin and all 50 patients were eventually discharged by the end of the study. But two of the 26 patients in a control group, who were not given the tablets, died.
Just one patient given calcifediol felt ill enough to be admitted to intensive care, whereas half of the participants in the control group were taken to ICU and two died.
But many scientists have criticised the study, saying its sample size is too small for any firm conclusions to be drawn about the impact of vitamin D.
Nonetheless, it was the most promising result for trials of the vitamin so far, and corresponds to earlier research that fixing vitamin deficiency might cut mortality rates by half.
A Northwestern University study, published in May, found Covid-19 patients with a severe vitamin D deficiency are twice as likely to experience major complications and die.
Nearly 99 per cent of Covid-19 patients who are vitamin D deficient die, according to a study from Indonesian researchers who analysed hospital records of 780 people who tested positive for SARS-CoV-2.
Results revealed 98.9 per cent of infected patients defined as vitamin D deficient — below 20ng/ml — died. Yet this fell to just 4.1 per cent for patients who had enough of the nutrient.
Researchers warned the study was not definitive, however, because the patients with high vitamin D levels were healthier and younger.
Another study by Tehran University, in Iran, and Boston University, found hospital Covid-19 patients who had sufficient vitamin D – of at least 30 ng/mL— were 51.5 per cent less likely to die from the disease.
The study of 235 hospitalized patients with Covid-19 also showed those with enough vitamin D had a significantly lower risk of falling seriously ill or needing ventilation.
Patients who had plenty of the nutrient also had less inflammation – often a deadly side effect of Covid-19.
However, there were flaws in these studies, such as a lack of acknowledgement of confounding factors, such as smoking, and social economic status, which were were not recorded for all patients but could have an impact on illness severity.
Some participants’ underlying health conditions were not defined, despite having a major impact on disease severity.
There have also been at least three studies which have suggested those who have enough vitamin D are less likely to catch the coronavirus in the first place.
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