Patients hospitalised with the coronavirus may endure less severe complications if their vitamin D levels are sufficiently high, research suggests.
The role of the sunshine supplement in warding off COVID-19, the disease caused by the infection, has been debated throughout the outbreak.
Vitamin D deficiency has been linked to an increased risk of viral respiratory infections in general, as well as inflammation.
When it comes to the coronavirus specifically, however, evidence was lacking.
To learn more, scientists from Boston University took blood samples from 235 patients hospitalised with the infection.
Results revealed those with adequate vitamin D levels – defined as at least 30 nanograms (ng)/mL – were significantly less likely to become unconscious, develop dangerously low oxygen levels or die.
“This study provides direct evidence that vitamin D sufficiency can reduce the complications, including the cytokine storm (release of too many proteins into the blood too quickly), and ultimately death from COVID-19,” said study author Dr Michael Holick.
Cytokines are proteins released by the immune system to help fight an infection. Although generally a positive step towards recovery, some patients overproduce cytokines, leading to a “storm”.
The proteins may then mistakenly attack healthy tissue, which could result in organ failure.
Vitamin D is an essential nutrient that helps keep bones, muscles and teeth healthy.
The NHS stresses “everyone should consider taking a daily supplement containing 10 micrograms of vitamin D during the autumn and winter”.
During the height of lockdown, Public Health England recommended people take vitamin D – despite the largely sunny weather – to counteract the effects of being housebound.
When it comes to warding off coronavirus complications, The Royal Society said in June “there is no direct causal link yet between vitamin D deficiency and increased susceptibility to COVID-19”.
The Scientific Advisory Committee on Nutrition echoed this, adding “overall, the evidence at this time does not support recommending vitamin D supplementation to prevent ARTIs [acute respiratory tract infections] in the general UK population”.
Dr Will Carroll from Keele University said at the time: “The best way to identify whether vitamin D has a role to play in helping the UK respond to the COVID-19 pandemic is to conduct a randomised clinical trial.”
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After measuring the vitamin D levels of 235 coronavirus patients, the Boston scientists found those with adequate amounts had reduced “clinical severity of the infection”.
Results – published in the journal PLOS One – revealed that in the patients over 40, those with sufficient vitamin D levels were 51.5% less likely to die with the infection than those whose levels were below 30ng/mL. One nanogram is one billionth of a gram.
Coronavirus cases are on the rise in the UK. On 24 September, 6,634 people tested positive for the infection, up from 3,395 the week before.
Experts have expressed concern the NHS could become overwhelmed in winter, when seasonal flu is also circulating.
“There is great concern the combination of an influenza infection and a coronal viral infection could substantially increase hospitalisations and death due to complications from these viral infections,” said Dr Holick.
The scientists believe vitamin D supplements could be a simple, inexpensive way of reducing the risk.
“Because vitamin D deficiency and insufficiency is so widespread in children and adults in the United States and worldwide, especially in the winter months, it is prudent for everyone to take a vitamin D supplement to reduce risk of being infected and having complications from COVID-19,” said Dr Holick.
In response to the study, a spokesperson from the Department of Health and Social Care said: “The latest review from NICE [National Institute for Health and Care Excellence] suggests no robust evidence for vitamin D supplements reducing the severity of COVID-19.
“However, this is a new virus and we keep all strong evidence on treatments under review.”
How much vitamin D do I need?
Adults and children over one-year-old require 10 micrograms of vitamin D a day.
The same goes for pregnant women, breastfeeding mothers and people at risk of vitamin D deficiency, like those who are housebound.
One microgram is 1,000 times less than a milligram. Ten micrograms is often written as 10μg.
Babies under one need between 8.5μg and 10μg of vitamin D a day.
The Department of Health and Social Care recommends breastfed babies be given a supplement via liquid drops.
Formula milk is fortified with the nutrient, therefore babies fed this way should not be given vitamin D until they are having less than 500ml a day.
Foods that contain vitamin D – like oily fish, liver, egg yolks and fortified cereals or spreads – also help you stay topped up, however, it is difficult to get sufficient levels from diet alone.