Vitamin D biological activity index in COVID-19: current concept and future challenges

Abstract

Vitamin D helps our immunity to fight viruses and bacteria, thus reducing the risk of respiratory infections. It suppresses the excessive or dysfunctional activities of immunity and prevents autoimmune diseases. In animal models vitamin D increases ACE2 on the cell surface, so its protection may not apply to COVID-19 since SARS-CoV-2 enters human cells by binding ACE2. On the other hand, ACE2 might make COVID-19 less severe, as it protects against lung damage. Observational and ecological studies are controversial regarding the association vit D levels - COVID-19 severity. Contradictory are the results of the way it influences the rate and duration of hospitalizations, ICU admissions and mortality.