Vitamin D and susceptibility to infectious diseases: no cure for the common cold

Abstract

Vitamin D influences innate immunity through up-regulation of antimicrobial peptides and adaptive immunity through modulation of both T-lymphocyte and B-lymphocyte function. Several observational studies have shown an association between low serum 25(OH)D levels and the incidence and severity of respiratory infections and also tuberculosis. Such studies, however do not fully account for confounding variables or reverse causality. The recent emergence of higher quality randomised controlled trials, however has so far not established a role for routine vitamin D supplementation in the general population for the prevention of respiratory infections. Further research, however may identify sub-groups to whom this intervention might be more appropriately targeted.