A review of Vitamin D effects on common respiratory diseases: Asthma, chronic obstructive pulmonary disease, and tuberculosis.

Despite the classic role of Vitamin D in skeletal health, new aspects of Vitamin D have been discovered in tissues and organs other than bones. Epidemiological and observational studies demonstrate a link between Vitamin D deficiency and risk of developing respiratory diseases including asthma, chronic obstructive pulmonary disease (COPD), and tuberculosis (TB). To review the literature, we searched the terms "Vitamin D" (using the set operator) and "asthma," "COPD" and "TB" in electronic databases, including PubMed/MEDLINE, Scopus, and Google Scholar until July 2015. Non-English articles or articles with unavailable full text were excluded. Both in vivo and in vitro studies were included. All the reviewed articles state that Vitamin D deficiency is very common among patients with respiratory diseases. The present data regarding Vitamin D and asthma is still controversial, but data about COPD and TB are more encouraging. The relevant studies have been conducted in different populations therefore it is not particularly possible to compare the data due to genetic variations. In order to point out a role for Vitamin D, large clinical trials with Vitamin D deficient subjects and sufficient Vitamin D supplementation are needed.