Vitamin D and respiratory infections.

Vitamin D or 1,25-hydroxyvitamin D (1,25(OH)2 D) has a well-established role in calcium homeostasis. In recent years, the discovery of vitamin D-metabolizing enzymes and vitamin D receptor (VDR) in the lungs and various cells of the immune system has led to numerous studies conducted to evaluate its role in respiratory functions and, in particular, upper respiratory tract infections (URTIs). A PubMed literature search was done using vitamin D and respiratory infections as key words. Only clinical studies were considered. This study aimed to review recent clinical and epidemiological studies conducted in adults and children, and to evaluate the functional role of vitamin D in respiratory infections. The evaluated studies show an important immunomodulatory role of vitamin D, which reduces the incidence and risk of URTIs, both in children and in adults. Combating URTIs can be done prophylactically, associating the use of vaccines against Streptococcus pneumoniae with strengthening the immune system through supplementation with vitamin D. These actions can significantly contribute to reducing the number of URTIs, the use of antibiotics, and consequently, the rates of antimicrobial resistance.