Vitamin D, innate immunity and upper respiratory tract infection.

INTRODUCTION: At the turn of the twentieth century, ultraviolet light was successfully used to treat tuberculosis of the skin. Upper respiratory tract infections had been inversely associated with sun exposure. During the last decade, basic scientific research demonstrated that vitamin D has an important anti-infective role.
METHOD: Review of the relevant literature on the influence of vitamin D on innate immunity and respiratory tract infection.
RESULTS: Vitamin D is involved in the production of defensins and cathelicidin - antimicrobial peptides that provide a natural defence against potential microbiological pathogens. Vitamin D supplementation increases cathelicidin production. Low vitamin D levels are associated with an increased incidence of upper respiratory tract infections.
CONCLUSIONS: Vitamin D appears to play an important role in the regulation of innate immunity in the upper respiratory tract. Optimal vitamin D levels and appropriate dosing schedules have yet to be determined.