In terms of the above renin-angiotensin system (RAS), vitamin D3 supplementation could modulate unbalanced RAS and ACE2 downregulation, resulting in induction of the ACE2/Ang-(1–7)/Mas receptor (MasR) axis for protection against ALI/ARDS [57] (Figure 3b). This evidence concerns the gene ACE2 and acute respiratory distress syndrome.