No evidence higher vitamin D levels improve Covid outcomes, study finds

Scientists investigating the link between vitamin D and Covid outcomes say evidence is lacking that higher levels of the sunshine vitamin lower the risk of falling seriously ill with the disease.

Researchers from Europe, Canada and Japan who analysed the records of more than 400,000 patients found “no evidence” to support the suggestion that higher levels of vitamin D improved coronavirus outcomes.

Specifically, they failed to find a link between vitamin D and the chances of catching the disease, the severity of the illness once caught, or the likelihood of a patient ending up in hospital.

“In multiple analyses, out results consistently showed no evidence for an association between genetically predicted vitamin D levels and Covid-19 susceptibility, hospitalisation or severe disease,” the study, which has not been peer-reviewed, said.

The report’s authors, who are affiliated with 10 global research institutions including King’s College London, looked at genetic variants associated with vitamin D among the 443,734 participants, meaning they could avoid being influenced by other factors, including age.

They said their findings, when looked at in conjunction with separate recent randomised trials, suggest other therapies should be prioritised for use against coronavirus.

“We did not find evidence that vitamin D supplementation in the general population would improve Covid-19 outcomes,” they said.

However they noted that their findings do not apply to individuals suffering from vitamin D deficiency, adding that “it remains possible that truly deficient patients may benefit from supplementation for Covid-19 related protection and outcomes”.

Vitamin D is key for healthy bones, teeth and muscles and deficiency has long been identified as a public health concern – an issue which affects people with an African, African-Caribbean or south Asian background more than others. Estimates suggest more than half the population of some European countries is deficient in the vitamin.

The NHS advises people to take vitamin D supplements if they have been indoors more than usual due to lockdowns, but says there is “currently not enough evidence to support taking vitamin D to prevent or treat coronavirus”.

Over the winter, free vitamin D supplements were offered to 2.7 million people on the “clinically extremely vulnerable” shielding list or who were living in residential and nursing care homes.

A second study by researchers at Aristotle University of Thessaloniki in Greece looked at coronavirus outcomes in 24 European countries and compared them with levels of vitamin D deficiency.

The report, which is also yet to be peer reviewed, found that the “prevalence of vitamin D deficiency was not significantly associated with either number of infections, recoveries or mortality rate” among Covid patients.

They said vitamin D supplements should only be advised for those belonging to groups at high risk of deficiency, “always under medical supervision and not as a preventive factor of Covid-19 infection”.

An article in The Lancet in January said data from observational studies suggested that vitamin D supplements can “lower the odds of developing respiratory infections, particularly in vitamin D-deficient groups, but randomised trials have yielded mixed results”.