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.
Vitamin supplements could cut women’s risk of catching Covid-19, study claims – but men don’t get the same protection
Vitamin supplements could reduce the risk of women getting Covid-19, a study has claimed.
King’s College London researchers used data from their Covid Symptom Study app and found taking the daily pills may reduce the virus risk by up to 14 per cent.
But the results were surprisingly specific – vitamin C and zinc, usually associated with the immune system, didn’t help and men didn’t get the same benefit as women.
Women taking vitamin D, multi-vitamins, omega-3 or probiotics appeared to be between nine and 14 per cent less likely to get Covid-19.
This means that, if the average risk of getting Covid was one in 10, those taking supplements could see their risk fall to around one in 12.
But scientists were very unsure of the results and said the study did not prove that the pills actually protected women, but may have been a sign of generally healthier lifestyles. The expert who led the study said people shouldn’t start trying to protect themselves with vitamins.
If women genuinely do get more protection, they suggested, it may be because they have generally tougher immune systems that respond better to supplements.
Overwhelming scientific evidence suggests the ‘sunshine vitamin’ may offer some protection against severe Covid-19, but some studies have claimed the proof isn’t strong enough.
The study was done on 372,720 users of the Covid Symptom Study app in the UK, who had reported what supplements they were taking at the start of the epidemic.
Around half of the group (175,652) said they regularly took supplements — at least three times a week — while the rest of the participants did not.
Tracking the volunteers over the course of Britain’s crisis, the researchers found that fewer women in the supplement group were testing positive than would have been expected.
They wrote in the study: ‘We observed a modest but significant association between use of probiotics, omega-3 fatty acid, multivitamin or vitamin D supplements and lower risk of testing positive for SARS-CoV-2 in women.
‘No clear benefits for men were observed nor any effect of vitamin C, garlic or zinc for men or women.’
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.
What have studies into vitamin D and Covid-19 shown?
By who? Cordoba University in Spain.
What did scientists study? 50 Covid-19 hospital patients with Covid-19 were given vitamin D. Their health outcomes were compared with 26 volunteers in a control group who were not given the tablets.
What did they find? Only one of the 50 patients needed intensive care and none died. Half of 26 virus sufferers who did not take vitamin D were later admitted to intensive care and two died.
What were the study’s limitations? Small pool of volunteers. Patients’ vitamin D levels were not checked before admission. Comorbidities were not taken into consideration.
By Who? University of Chicago.
What did scientists study? 500 Americans’ vitamin D levels were tested. Researchers then compared volunteers’ levels with how many caught coronavirus.
What did they find? 60 per cent higher rates of Covid-19 among people with low levels of the ‘sunshine vitamin’.
What were the study’s limitations?
Researchers did not check for other compounding factors. Unclear whether or not volunteers were vitamin D deficient at the time of their coronavirus tests. People’s age, job and where they lived – factors which greatly increase the chance of contracting the virus – were not considered.
By Who? Tehran University, in Iran, and Boston University.
What did scientists study? Analysed data from 235 hospitalized patients with Covid-19.
What did they find? Patients who had sufficient vitamin D – of at least 30 ng/mL— were 51.5 per cent less likely to die from the disease. They also 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.
What were the study’s limitations? Confounding factors, such as smoking, and social economic status were not recorded for all patients and could have an impact on illness severity.
By Who? Tel Aviv University, Israel.
What did scientists study? 782 people who tested positive for coronavirus had their vitamin d levels prior to infection assessed retrospectively and compared to healthy people.
What did they find? People with vitamin D levels below 30 ng/ml – optimal – were 45 per cent more likely to test positive and 95 per cent more likely to be hospitalised.
What were the study’s limitations? Did not look at underlying health conditions and did not check vitamin D levels at the time of infection.
By Who? Brussels Free University.
What did scientists study? Compared vitamin D levels in almost 200 Covid-19 hospital patients with a control group of more than 2,000 healthy people.
What did they find? Men who were hospitalised with the infection were significantly more likely to have a vitamin D deficiency than healthy men of the same age. Deficiency rates were 67 per cent in the COVID-19 patient group, and 49 per cent in the control group. The same was not found for women.
What were the study’s limitations? Independent scientists say blood vitamin D levels go down when people develop serious illness, which the study did not take into consideration. This suggests that it is the illness that is leading to lower blood vitamin D levels in this study, and not the other way around.
By who? Inha University in Incheon, South Korea.
What did scientists study? 50 hospital patients with Covid-19 were checked for levels of all vital vitamins and compared to a control group.
What did they find? 76 per cent of them were deficient in vitamin D, and a severe vitamin D deficiency (<10 ng/dl) was found in 24 per cent of Covid-19 patients and just 7 per cent in the control group.
What were the study’s limitations?
Small sample size and researchers never accounted for vitamin levels dropping when they fall ill.
By Who?. Independent scientists in Indonesia.
What did scientists study? Checked vitamin D levels in 780 Covid-19 hospital patients.
What did they find? Almost 99% of patients who died had vitamin D deficiency. Of patients with vitamin D levels higher than 30 ng/ml – considered optimal – only per cent died.
What were the study’s limitations? It was not peer-reviewed by fellow scientists, a process that often uncovers flaws in studies.
By Who? University of Glasgow.
What did scientists study? Vitamin D levels in 449 people from the UK Biobank who had confirmed Covid-19 infection.
What did they find? Vitamin D deficiency was associated with an increased risk in infection – but not after adjustment for con-founders such as ethnicity. It led to the team to conclude their ‘findings do not support a potential link between vitamin D concentrations and risk of Covid-19 infection.’
What were the study’s limitations? Vitamin D levels were taken 10 to 14 years beforehand.
By Who? University of East Anglia.
What did scientists study? Average levels of vitamin D in populations of 20 European countries were compared with Covid-19 infection and death rates at the time.
What did they find? The mean level of vitamin D in each country was ‘strongly associated’ with higher levels of Covid-19 cases and deaths. The authors said at the time: ‘The most vulnerable group of population for Covid-19 is also the one that has the most deficit in vitamin D.’
What were the study’s limitations? The number of cases in each country was affected by the number of tests performed, as well as the different measures taken by each country to prevent the spread of infection. And it only looked at correlation, not causation.
By Who? Northwestern University.
What did scientists study? Crunched data from dozens of studies around the world that included vitamin D levels among Covid-19 patients.
What did they find? Patients with a severe deficiency are twice as likely to experience major complications and die.
What were the study’s limitations? Cases and deaths in each country was affected by the number of tests performed.