The results of a new clinical trial suggest that vitamin D supplements are not helping people hospitalized with moderate to severe covid-19. Elsewhere, a controversial and preliminary article suggesting that vitamin D did offer a benefit was now withdrawn by the Lancet because of “concerns” about the study design.
Vitamin D has emerged as a new covid-19 panacea for some on social media, replacing previous favorites like hydroxychloroquine. There is plenty proof that many people could use more vitamin D every day in their lives, especially in winter. Deficiency of this vitamin, which can be taken as a supplement or synthesized in the skin under strong sunlight, can certainly affect people’s overall health. But the evidence that vitamin D plays a major factor in the severity of covid-19 or that supplementation can help it treat ongoing cases is much less solid.
A study will follow at the end of January released on the preprint server SSRN – operated by The Lancet magazine – that picture seemed to change. The authors claimed to have found that calcifediol (a byproduct of vitamin D) reduced the risk of death in covid-19 patients hospitalized in Spain by as much as 60% compared to people receiving standard care. In comparison, tocilizumab was the arthritis drug recently found to reduce mortality in severe covid-19 patients by 4% in a large UK study – modest results promising enough to likely anchor it as a standard treatment alongside steroids for critical cases.
But it didn’t take long for outside scientists started to raise problems with those results. For example, the study design was described as both a randomized and an observational study by the authors at different points in the paper – two very different things. Randomized trials, where some people are randomly assigned to receive treatment, are considered the gold standard of clinical evidence because they can better confirm that a drug has a real, beneficial effect on a disease. Observational studies, in which scientists simply observe the differences between groups of people receiving different care, are important in medicine, but their conclusions are generally viewed with more caution as it is more difficult to know whether a particular treatment caused the effect . Other criticisms of the paper included a lack of relevant data on patients (such as some patients’ baseline vitamin D levels), as well as possible statistical shortcomings. And of course, anyway, the findings would still be preliminary as they haven’t gone through the peer review process yet.
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Friday, The Lancet deleted the article from the preprint server, citing ‘concerns about the description of the study in this article’. It also announced that it would launch an investigation into the investigation.
Meanwhile, the results were what appears to be a true randomized vitamin D trial for covid-19 published Wednesday in the Journal of American Medical Association – largest study of its kind to date. Researchers in Brazil said they randomized 240 people with moderate to severe covid-19 in the hospital to receive a single large dose of vitamin D (200,000 IU, compared to the daily dose of 600-800 IU recommended for the average adult) or a placebo.
Altogether, they found no difference in the length of hospital stay between people who took vitamin D and those who didn’t. There was also no difference in the mortality rate or other important measures, such as the likelihood of someone needing invasive ventilation. And while the treatment seemed safe, one patient had an episode of vomiting that was likely associated with it.
“The findings do not support the use of a high dose of vitamin D3 for the treatment of moderate to severe COVID-19,” the authors wrote.
The JAMA study is just one more study and nothing should be decided in medicine based on a single study. And again, too many people aren’t getting as much vitamin D as they need anyway, so there’s nothing wrong with checking your levels with the help of a doctor. But the pandemic has seen countless others possible treatments come and go with little effectiveness to show for it.
In general, it is difficult to test for the specific effect of vitamin D intake on any condition as it is often an indicator of other things. For example, someone with high vitamin D levels could also be someone who often exercises outside, and it could be the workout or their overall good health that really provides a protective boost.
If vitamin D has a benefit to covid-19, it’s probably modest at best. And the lack of enthusiasm about this Treatment is by no means evidence of a grand conspiracy in which doctors downplay vitamin D just to charge for more expensive drugs, as some have suggested. After all, the most successful and life-saving drug for covid-19 to date is dexamethasone, a generic steroid that can cost less than $ 10 per treatment.