Abstract

Coronaviruses belong to a large family of viruses (Coronaviridae) that infect birds and various mammals. The novel coronavirus currently known as SARS-CoV-2 was discovered in December 2019 in Wuhan, Hubei province, China and is the causal agent of the current atypical pneumonia epidemic (COVID-19: Coronavirus Disease 2019).
The most severe cases present with acute respiratory distress syndrome that can lead to death. Vitamin D (VD) has a pleiotropic effect on several organs, in addition to its wellknown and positive effect on bone health and calcium homeostasis, with an almost universal distribution of the VD receptor and the metabolites of 25hydroxyvitamin D (25OHD) in all cells of the body. These extra-skeletal actions depend on the synthesis of the active metabolite 1,25dihydroxyvitamin D in the cells depending on the optimal circulating levels of 25OHD and though paracrine and autocrine regulation. Due to its immunomodulatory, anti-inflammatory, antimicrobial, and regulatory actions on the renin angiotensin aldosterone system, which favors the compensation of the respiratory epithelium and cellular redox homeostasis, the VD could have a protective effect on COVID-19 infection. Among the risk groups for COVID-19 are obese, diabetic, and hypertensive patients, subjects with cardiovascular conditions, and elderly people. All these pathologies show a higher incidence in individuals with VD hypovitaminosis. VD supplementation, to achieve optimal 25OHD levels of 40-60 ng/ml, could reduce the incidence, severity, and risk of death in the current COVID-19 pandemic, as a complementary measure while the vaccine and other specific therapies are being developed.

Key words: vitamin D, COVID-19, supplementation, immunology, SRAA, prevention.