Since the beginning of the pandemic, many researchers focused on the possible effect of vitamin D deficiency on the pathophysiology, clinical manifestation and outcomes of Sars-CoV-2 infection. Evidence gleaned from retrospective and observational studies reported an inverse relationship between serum vitamin D levels and COVID-19. Possible mutual relationships between perturbation of vitamin D metabolism and immunological mechanisms associated with COVID-19 have been described, as well.
In the attempt of best defining this interesting topic, randomized controlled trials have been carrying out with the rationale of a beneficial effect of vitamin D supplementation on several outcomes related to Sars-CoV-2 infection.
The article by Villasis-Keever et al. is a recent interesting contribution in the field. The authors employed a daily 4,000 IU dose of cholecalciferol as a preventive measure that was administered to 94 Sars-Cov-2-negative healthcare workers for 30 days. A placebo group of 98 subjects was assessed. All were high risk subjects, as they were employed in Covid 19 wards. Results demostrated that vitamin D administration was associated with lower risk of Sars-CoV-2 infection independently of baseline serum vitamin D levels. Interestingly, the increase in vitamin D levels was found to be a significant predictor of the risk of infection. Results were confirmed after adjustment for age and comorbidities.
Notwithstanding the limit of a study that showed high rate of discontinuation (56 in the vitamin D and 54 in the placebo group) and whose evaluation of confounding factors should be more deeply discussed, the article opens new and interesting questions on how vitamin D may be effectively empolyed on a regular basis for disease prevention and which could be the pathophysiological mechanisms of protection from Sars-Cov-2 infection associated with vitamin D administration. Finally, is there any space for an eventual protection from other infective respiratory disease offered by vitamin D repletion?