Does Vitamin D protect against coronavirus?

Can Vitamin D help protect against coronavirus? Are the Vitamin D deficient more at risk from the virus? There is a wave of interest in these questions with media reports suggesting that Vitamin D is useful in fighting coronavirus. But as things stand evidence to support these claims is limited and Vitamin D seems at best a promising lead.

Vitamin D is known to play a vital role in maintaining the health of our bones, teeth, and muscles. There is also a growing body of evidence that it plays an important role in the immune system, and some studies have suggested that it might help protect against respiratory infections specifically though this remains debated.

As such, a number of reports have suggested that Vitamin D deficiency could make patients more susceptible to catching coronavirus, and/or that Vitamin D supplements could help treat the virus.

Vitamin D deficiency might also go some way in explaining why some groups are more susceptible to coronavirus.

Most of our Vitamin D is synthesised by the body when it is exposed to sunlight, and while small quantities can be obtained through food such oily fish, egg yolks, and red meat this is rarely enough. As such, Vitamin D deficiency which is relatively common in the UK between October and early March when exposure to sunlight is reduced – and roughly 20% of Britons are deficient throughout the year.

A number of groups are particularly at risk of Vitamin D deficiency. As Vitamin D is distributed in fat tissues the obese often suffer from low levels in their blood. Other groups ,such as the elderly, often spend less time outside than the general population and thus have less opportunity to synthesise Vitamin D. Additionally, since darker skin inhibits Vitamin D synthesis BAME people, in particular those of African or South Asian origin, are more likely to be Vitamin D deficient in the UK.

Indeed, a recent study by Surrey and Southampton universities looking into the possible link between Vitamin D levels and coronavirus has thrown light on the levels of disparity. Comparing the blood samples of 1,300 adults from the UK Biobank health monitoring programme they found that Vitamin D levels were typically 53% higher among white people than among BAME persons, and 25% higher among those of a healthy weight than the obese.

Notably, all these groups have proved particularly vulnerable to coronavirus. The higher rate of death among BAME people than the general population has been a particular area of concern, sparking calls for a public enquiry.

Other groups such Vitamin D deficient infants do not seem to be more vulnerable to the virus.

Correlation is not the same as causation, and as things stand the consensus is that we do not as yet have a sufficient evidence to prove whether or nor Vitamin D might be an effective coronavirus treatment or prophylactic. Indeed, even the studies most enthusiastic about the potential of Vitamin D as a treatment emphasise that further testing in the form of randomised trials is needed.

If Vitamin D does provide some protection against coronavirus it will almost certainly not be a “magic bullet” in the words a recent paper published in the BMJ’s Nutrition, Prevention, and Health Section. Instead, as the paper said, while “further research is justified”, potential use of Vitamin D supplements should been seen as part of a wider “healthy lifestyle strategy”. It should also be noted that large doses of Vitamin D, as suggested by some studies, carry the risk of causing calcium to build up in the body damaging the heart, the kidneys, and bones.

Official NHS guidelines state that “There have been some news reports about vitamin D reducing the risk of coronavirus. However, there is no evidence that this is the case.”

Still, the NHS does recommend that people consider taking a small quantity, 10 micrograms, of Vitamin D a day in order to help preserve bone and muscle health since lockdown is reducing our exposure to sunlight.