The roles of vitamin D in increasing the body's immunity and reducing injuries due to viral infections: With an emphasis on its possible role in SARS-CoV-2 (COVID-19).

Background It is known that Vitamin D can increase the body's immunity against some viral infections. Many people around the world have vitamin D deficiency and, therefore, this has become a public concern whether vitamin D is an important factor protecting against COVID-19 infection. In this paper, the data about the roles of vitamin D on immunity and recovery from viral infections, especially novel Coronavirus disease (COVID-19) is reviewed. Methods The electronic databases of Pubmed, Google Scholar, Research Gate, Excerpta Media Database (EMBASE) and Medical and Health Education (Medrix) were searched. Results Vitamin D is considered an important factor in immune homeostasis. Various effects have been considered for this nutrient on the immune system, particularly because of vitamin D receptor (VDR) and Cytochrome P450 Family 27 Subfamily B Member 1 (CYP27B1) expression in most of the immune cells. Vitamin D can raise cellular immunity, reduce cytokine storm and enhance antioxidants production. It also has modulatory effects on Angiotensin-converting enzyme 2 (ACE2) receptors and might have protective functions against acute lung injuries, including COVID-19 infection. However, there are some articles against this positive effect. Conclusion Vitamin D supplementation is reported to be effective in the enhancement of the immune system and might be effective in the treatment and prevention of COVID-19 infection, especially in those with its deficiency. However, it should be considered that vitamin D deficiency shows the overall health status of the patients and cannot be considered specific for COVID-19 infection.Recent Advances in Anti-Infective Drug Discovery.