Table 4.

Summary

Vitamin D deficiency as a possible factor determining COVID‐19 severity Lower population mortality in countries South of 28 degrees N latitude where there will have been sufficient sunlight to maintain vitamin D levels during the past months. Vitamin D deficiency correlates with hypertension, diabetes, obesity, ethnicity and institutionalization all of which are features associated with increased risk of severe COVID‐19. Vitamin D moderates inflammatory cytokine response by macrophages and respiratory epithelial cells to pathogens including respiratory viruses. Vitamin D’s effect on cytokines and reduced risk for experimental lung injury is likely mediated by its increase in ACE2:ACE ratio and consequential reduction of angiotensin II – highly relevant to COVID‐19 since ACE2 is the SARS‐CoV‐2 receptor. Vitamin D deficiency and vitamin D receptor polymorphisms are associated with increased risk of severe viral bronchiolitis in infants. Vitamin D deficiency is easily prevented by supplementation which is very safe.