Preclinical data strongly suggest that the
vitamin D endocrine system (VDES) may have extraskeletal effects. Cells of the immune and cardiovascular systems and lungs can express the
vitamin D receptor, and overall these cells respond in a coherent fashion when exposed to
1,25-dihydroxyvitamin D, the main metabolite of the VDES. Supplementation of
vitamin D-deficient subjects may decrease the risk of
upper respiratory infections. The VDES also has broad anti-inflammatory and anti-thrombotic effects, and other mechanisms argue for a potential beneficial effect of a good
vitamin D status on
acute respiratory distress syndrome, a major complication of this SARS-2/
COVID-19 infection. Activation of the VDES may thus have beneficial effects on the severity of
COVID-19. Meta-analysis of observational data show that a better
vitamin D status decreased the requirement of
intensive care treatment or decreased mortality. A pilot study in Cordoba indicated that admission to
intensive care was drastically reduced by administration of a high dose of
calcifediol early after hospital admission for
COVID-19. A large observational study in Barcelona confirmed that such
therapy significantly decreased the odds ratio (OR) of mortality (OR = 0.52). This was also the conclusion of a retrospective study in five hospitals of Southern Spain. A retrospective study on all Andalusian patients hospitalized because of
COVID-19, based on real-world data from the health care system, concluded that prescription of
calcifediol (hazard ratio [HR] = 0.67) or
vitamin D (HR = 0.75), 15 days before hospital admission decreased mortality within the first month. In conclusion, a good
vitamin D status may have beneficial effects on the course of
COVID-19. This needs to be confirmed by large, randomized trials, but in the meantime, we recommend (rapid) correction of 25 hydroxyvitamin D (25OHD) deficiency in subjects exposed to this coronavirus. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and
Mineral Research.