Table 1.

Summary of the symptoms contributing to COVID-19 pathogenesis and evidence for how vitamin D may be effective in combatting them

Features of COVID-19 pathogenesis	Effect of vitamin D on COVID-19
1. Angiotensin II and the renin-angiotensin system
SARS-CoV-2 binds to ACE2 on alveolar cells [86] and impairs ratio of ACE2/ACE activity, which as a consequence, increases angiotensin II [88]	Increases ACE2 expression (98) and inhibits renin [101], both of which reduce angiotensin II levels
2. Inflammatory cytokine storm
Increases production of pro-inflammatory cytokines leading to a cytokine storm [85, 89, 90]	Decreases production of pro-inflammatory cytokines (e.g. IL-6) that contribute to cytokine storm [97]
3. Cardiopulmonary injury
Severe COVID-19 cases result in ARDS, pulmonary edema, cardiovascular injury, coagulopathies [82, 91], and thrombotic events [107]	Poor vitamin D status is associated with increased risk of cardiovascular outcomes and thrombosis [48, 103–106] 1,25D promotes production of cathelicidin, which can attenuate lung injury in a rat model of hyperoxia (102)