Can Vitamin D Supplementation Protect Health Care Workers From COVID-19?

Vitamin D capsules.
Does vitamin D supplementation effectively prevent COVID-19 infection in those with high exposure to infected individuals — and is it safe?

Vitamin D supplements may help individuals with high exposure to COVID-19 prevent infection without causing serious adverse events, according to study findings published in Archives of Medical Research.

Previous research suggests risk of viral and bacterial infections are associated with vitamin D deficiency. Other recent studies involving vitamin D and patients with COVID-19 have produced a variety of inconsistent results. Researchers sought to investigate the efficacy of vitamin D supplementation in preventing SARS-CoV-2 infection in individuals with high exposure to COVID-19 by assessing the efficacy of supplementation in health care workers with frontline exposure to patients with COVID-19. Infection rate and disease severity were the primary endpoints, with safety as a secondary endpoint.

Study researchers conducted a double-blind, parallel, randomized trial ( Identifier: NCT04535791) of 321 frontline health care workers recruited from 4 Mexico City hospitals who tested negative for SARS-CoV-2 between mid-July and end-of-year 2020. Participants were randomly assigned to a vitamin D group (n=160; median age, 36.0 years; 71% female) receiving 4000 IU vitamin D daily for 30 days and a placebo group (n=161; median age, 39.0 years; 68% female). The risk factors present among individuals in the vitamin D and placebo groups were hypertension (26.9% vs 32.3%, respectively), obesity (26.3% vs 24.8%), migraine and rheumatoid arthritis (11.9% vs 11.8%), and vitamin D3 deficiency (63.8% vs 70.2%) at baseline. Of these participants, 94 of the vitamin D group and 98 of the placebo group completed follow-up. Antibody and serum 25-hydroxyvitamin D3 tests were conducted at baseline and day 45. RT-PCR tests were also administered at baseline and repeated if COVID-19 symptoms emerged.

Researchers found a reduced SARS-CoV-2 infection rate in the vitamin D group compared with placebo group (6.4 vs 24.5%, P <.001). The vitamin D group showed a lower risk of acquiring SARS-CoV-2 infection compared with placebo group (RR: 0.23; 95% CI, 0.09-0.55) and an increase in serum levels of 25-hydroxyvitamin D3 was associated (RR: 0.87; 95% CI, 0.82-0.93), regardless of a vitamin D deficiency. Adverse events were not considered significant and reported by 36.7% of placebo and 22.3% of vitamin D group, mostly headache, constipation, diarrhea, drowsiness, and muscular weakness.

Study limitations included a nonresponse bias due to the high drop-out rate of recruited individuals.

“Our results suggest that [vitamin D] supplementation in highly exposed individuals prevents SARS-CoV-2 infection without serious AEs and regardless of [vitamin D]  status,” researchers concluded.


Villasis-Keever MA, López-Alarcón MG, Miranda-Novales G, et al. Efficacy and safety of vitamin D supplementation to prevent COVID-19 in frontline healthcare workers. A randomized clinical trial. Arch Med Res. Published online April 18, 2022. doi:10.1016/j.arcmed.2022.04.003

This article originally appeared on Pulmonology Advisor