Vitamin D Supplementation Probably Doesn’t Prevent Covid-19

A strong answer to a question that has been asked for the whole pandemic

Pictured: Not a COVID-19 preventative, apparently. Source: Unsplash

Vitamin D is one of the most popular supplements in the world. Because it’s involved in numerous biological processes, and people with low levels of vitamin D are worse off in so many ways than people with higher levels, there’s long been a thought that it would help with everything from heart disease to cancer.

Of course, the fact that the supplement is mostly harmless and plausibly beneficial doesn’t hurt the case either. And, given the evidence that vitamin D might have some benefit against cold/flu, many people have been arguing since the start of the Covid-19 pandemic that a supplement of the vitamin might not just help people with coronavirus but actually prevent the disease entirely.

Antoher source of vitamin D. Not as profitable as supplements, and not as regularly recommended, but maybe that’s just the cynic in me talking. Source: Unsplash

It’s worth noting that if vitamin D worked against Covid-19 or even other respiratory infections this would indeed be a wonderful thing. It’s a cheap, easily produced and very safe supplement that people can take en mass without serious worries. If that prevented Covid-19, those of us in the medical world would be jumping for joy.

However, a new large randomized trial has just been preprinted looking at whether treating vitamin D deficiency can prevent Covid-19 and other acute respiratory infections. Unfortunately, the answer looks like a very solid, resounding no.

The Science

The study in question is called Coronavit, and is currently up on the preprint server medrxiv. Starting at the end of 2020, the authors randomized about 6,000 people in the UK to be invited into one of three programs — a program where they got a vitamin D test and if deficient were given either high or low supplementation, or a program with no test and no supplementation. In all, 1,500 people got invited to high-dose vitamin D, 1,500 to low-dose, and about 3,000 received no intervention.

Six months later, the researchers then checked whether the participants had gotten either a doctor-diagnosed acute respiratory illness…