Calcitriol regulates the expression of antimicrobial proteins (cathelicidin and defensin), which directly kill pathogens, especially bacteria [99]. It inhibits the production of IFN-γ [71] and reduces the expression of pro-inflammatory cytokines by increasing the expression of anti-inflammatory cytokines by macrophages [105]. Calcitriol modulates antimicrobial proteins (cathelicidin and β-defensin), responsible for modifying the intestinal microbiota, favoring a healthy composition and supporting the intestinal barrier [80, 106]. It also helps protect the lungs against infection, increases the expression of the tight junction protein, E-cadherin and connexion 43 in the intestine, maintains renal-epithelial barrier function and improves corneal epithelial barrier function [104].