Recent headlines have suggested vitamin D deficiency could increase the risk of dying from COVID-19, and in turn, that we should consider taking vitamin D supplements to protect ourselves.

Is this all just hype, or could vitamin D really help in the fight against COVID-19.

Six things you need to know about your vitamin D levels.

Some scientists have suggested vitamin D might help to alleviate the “cytokine storm” described in the most severe COVID-19 cases.

Evidence from randomised controlled trials suggests regular vitamin D supplementation may help protect against acute respiratory infections.

The benefits of regular supplementation were greatest among participants who were severely vitamin D deficient to begin with, for whom the risk of respiratory infection went down by 70%.

We still have relatively little direct evidence about the role of vitamin D in COVID-19.

For example, one small study from the United States and another study from Asia found a strong correlation between low vitamin D status and severe infection with COVID-19.

Studies assessing ICU patients have reported high rates of deficiency even before COVID-19.

So we would expect to see relatively high rates of vitamin D deficiency in seriously ill COVID-19 patients – whether vitamin D has a role or not.

Some researchers have noted high rates of COVID-19 infections in ethnic minority groups in the UK and US to suggest a role for vitamin D, as ethnic minority groups tend to have lower levels of vitamin D.

However, analyses from the UK Biobank did not support a link between vitamin D concentrations and risk of COVID-19 infection, nor that vitamin D concentration might explain ethnic differences in getting a COVID-19 infection.

Although this research adjusted for confounders, vitamin D levels were measured ten years earlier, which is a drawback.

Researchers have also suggested vitamin D plays a role by looking at the average vitamin D levels of different countries alongside their COVID-19 infections

So hopefully in time we’ll get some more clarity about the potential effects of vitamin D on COVID-19 infection, particularly from studies using stronger designs

In the meantime, even if we don’t know whether vitamin D can help mitigate the risk of or outcomes from COVID-19, we do know being vitamin D deficient won’t help