Vitamin D is known for its roles in calcium metabolism and bone health. With the spread of COVID-19 epidemic, roles of this vitamin in strengthening host immune system has received more attention. Nearly 900 genes have been identified, whose expression is controlled by vitamin D. Most of these genes are involved in innate and adaptive immune systems.
Vitamin D prohibits the penetration of viruses deep into tissues by maintaining intercellular connections. This characteristic of vitamin D prevents rapid spread of the coronavirus in the lungs. Stimulating immune cell differentiation, increasing killing capacity of macrophages and increasing production of
antimicrobial peptides such as cathelicidin and β-defensin by vitamin D increase the immune system ability to fight coronavirus. Moreover, vitamin D decreases over secretion of inflammatory cytokines; thus, prohibiting
cytokine storm and uncontrolled inflammation in the lungs. Modulating activity of the renin-angiotensin system and preventing over accumulation of angiotensin 2 are other functions of vitamin D in protecting tissues, especially lungs, against the coronavirus.
