The D-side of COVID-19: musculoskeletal benefits of vitamin D and beyond.

Coronavirus 2019 disease (COVID-19) mostly adversely affects the elderly, a population at higher risk for low serum 25-hydroxyvitamin D (25(OH)D) levels. In this viewpoint, we highlight the well-known musculoskeletal properties of vitamin D, which are particularly relevant in the context of COVID-19, suggesting further potential benefits through extra-skeletal effects. Maintaining optimal 25(OH)D is crucial to prevent falls, frailty and fractures in elderly patients, with low activity levels due to lockdown, or who are relatively immobilized during hospitalization and after discharge for prolonged periods of time. Hypovitaminosis D is also associated with susceptibility to respiratory infections, admissions to the intensive care unit, and mortality. We underscore the importance of achieving desirable serum 25(OH)D in COVID-19 elderly patients, to ensure beneficial musculoskeletal effects and possibly respiratory effects of vitamin D, in the context of COVID-19.