vitamin d: both a supplement and a covid-19 treatment?

earlier this year in the spring, 76 spanish covid-19 patients with acute respiratory infection were hospitalized. dr. jose manuel quesada-gomez gave 50 of them high doses of calcifediol — the equivalent of swallowing two fistfuls of fast-acting vitamin d supplement pills. only two per cent of the vitamin d group ended up in the intensive care unit and none died, while 50 per cent of the other group required advanced care and two died. these are remarkable results — almost too good to be true.

since the pandemic began, a plethora of studies have been published connecting covid-19 outcomes to vitamin d levels . in a study of covid-19 mortality in indonesia , the majority of the 780 individuals who died were vitamin d deficient. multiple groups have also published retrospective case-control studies establishing strong correlations between low vitamin d levels and increased covid-19 risk or severity . and it is hard to ignore the striking overlap in the risk factors for severe covid-19 and vitamin d deficiency, including older age, obesity, and darker skin.

however, none of these studies can prove cause-and-effect, so they are quickly discounted in many circles . the small study from spain has been criticized for not using a double-blind placebo control group, relying on small sample sizes, and using multiple other treatment methods on top of calcifediol. challengers also note that they don’t take into account confounding variables , like obesity, or account for reverse causality.

vitamin d disappointment

as an author of one of these failed clinical trials on vitamin d, professor adrian martineau at the queen mary university of london doubts that it could change the course of covid-19 infection. he describes two treatment opportunities: reduce virus proliferation in the first phase and suppress the inflammatory response in the second phase of the disease. to be a valuable treatment option, vitamin d has to prove effective above and beyond antivirals or immunosuppressants already prescribed.

vitamin d advocates, like dr. william grant from the sunlight, nutrition, and health research center , are frustrated by this dismissive response.

trained as an endocrinologist at harvard, adams has been studying how vitamin d modulates the immune system for three decades in his laboratory at the university of california, los angeles. the team has found that after vitamin d is made in the skin and converted into its active form, it enters immune cells called macrophages. these large pac-man-like cells are the first line of defence against invading viruses. vitamin d activates them and charges up the innate immune response . “so we consider the use of vitamin d as you would consider the use of an antibiotic… not as something that you give as a vitamin or a dietary supplement.”

“what we’re doing is giving fuel to the inflammatory system or the innate immune system to deal with the challenge of covid as effectively as it possibly can,” he says.

this strategy aims to handle the virus before any larger adaptive immune system response or cytokine storm is triggered. martineau concedes that vitamin d may be able to reduce the severity of covid-19, but gives it a “50/50” chance of having any effect over and above other drugs.

adams expects results by next spring. vitamin d may or may not become more than a dietary supplement — capable of protecting nearly one billion vitamin d deficient people in the world from covid-19. “we are hopeful… but it’s a controlled study. it is a scientific study,” he says. “it may turn out not to be effective therapy, but at least we’ll know one way or another.”