The role of vitamin D (VitD) in calcium and bone homeostasis is well described. In the last years, it has been
recognized that in addition to this classical function, VitD modulates a variety of processes and regulatory systems
including host defense, inflammation, immunity, and repair. VitD deficiency appears to be frequent in industrialized
countries. Especially patients with lung diseases have often low VitD serum levels. Epidemiological data indicate
that low levels of serum VitD is associated with impaired pulmonary function, increased incidence of inflammatory,
infectious or neoplastic diseases. Several lung diseases, all inflammatory in nature, may be related to activities of
VitD including asthma, COPD and cancer. The exact mechanisms underlying these data are unknown, however,
VitD appears to impact on the function of inflammatory and structural cells, including dendritic cells, lymphocytes,
monocytes, and epithelial cells. This review summarizes the knowledge on the classical and newly discovered
functions of VitD, the molecular and cellular mechanism of action and the available data on the relationship
between lung disease and VitD status.
