Two large, independent trials from distinct health centers report that vitamin D supplementation does not lower the chance of catching COVID-19 or other acute respiratory infections. The findings come from studies conducted under the oversight of Queen Mary University and University Hospital Oslo, and the results were published in the medical journal BMJ. This adds to a growing body of evidence that vitamin D supplementation may not offer preventive benefits against respiratory infections in general or against COVID-19 specifically.
In the first study, a UK cohort of six thousand two hundred adults aged sixteen and older, who were not taking vitamin D supplements at the outset, participated between December of the year two thousand twenty and June of the following year. A random portion of participants received a blood test to determine their vitamin D status. Among those with low vitamin D levels, which included the majority of the group, interventions were triggered to supplement the diet with either three thousand two hundred international units per day or eight hundred international units per day for a duration of six months. The remaining participants did not receive vitamin D and served as a comparison group. Throughout the six months of follow up, neither dosage influenced the occurrence of acute respiratory infections nor the incidence of PCR-confirmed COVID-19 cases. Adverse events occurred at similar rates in both arms, and there were no serious adverse events tied to vitamin D intake.
The second trial took place in Norway and ran from November of the same year through June of the following year. About thirty five thousand adults, aged eighteen to seventy five, who were not using vitamin D supplements at the start, were enrolled. Participants were split into two equal groups. One group received five milliliters of cod liver oil daily for six months, while the other group received a placebo consisting of five milliliters of corn oil. At baseline, the majority of participants had sufficient vitamin D levels. The study found no impact of cod liver oil on the rate of acute respiratory infections or on PCR-confirmed COVID-19 cases. Adverse effects were negligible and did not differ meaningfully from those in the placebo group. The two groups showed comparable safety profiles throughout the trial period.
These findings align with earlier research that did not observe a preventive effect from vitamin D on the risk of contracting COVID-19. In other words, taking vitamin D supplements or cod liver oil did not demonstrably reduce the likelihood of infection in the studied populations, suggesting that routine vitamin D supplementation should not be recommended solely for the purpose of preventing COVID-19 or other acute respiratory infections in similar settings.