Vitamin D may help reduce the risk of long COVID, study suggests

A randomized trial of more than 1,700 adults found that people given daily vitamin D3 for four weeks showed a modestly lower rate of persistent symptoms at eight weeks (21% vs 25%); researchers reported no difference in acute COVID severity, hospital visits, or deaths between the vitamin D and placebo groups.

Researchers report a randomized trial that found a suggestive benefit of vitamin D supplementation against developing long COVID. The study, published in The Journal of Nutrition, enrolled more than 1,700 adults in the United States and Mongolia and 277 household contacts. Participants were randomly assigned to receive a daily vitamin D3 supplement or placebo for four weeks, with the treatment starting on average three days after a positive COVID-19 test. Investigators observed a modest signal of lower rates of persistent symptoms at eight weeks among those who adhered to the vitamin D regimen. Key findings: - The trial enrolled over 1,700 adults who recently tested positive for COVID-19 and 277 household members who had contact with infected participants. - Participants were randomized to daily vitamin D3 or placebo for four weeks; the average time from positive test to starting the regimen was three days. - At eight weeks, 21% of people in the vitamin D group reported at least one persistent symptom versus 25% in the placebo group, a difference described as a signal for reduced risk. - There was no observed difference between groups over the four-week period in hospitalizations, clinic visits, emergency department trips, deaths, or acute COVID symptom severity. - Taking high-dose vitamin D did not reduce the rate of household members contracting COVID-19. - Study authors said the findings are suggestive and that a larger randomized trial is needed to provide greater statistical certainty. Summary: The trial's results suggest vitamin D supplementation could be associated with a modestly lower risk of persistent post-COVID symptoms but did not affect measures of acute illness in this study. Researchers describe the finding as preliminary and recommend larger randomized studies to clarify the effect and provide greater statistical certainty.