We don't know what the mechanism is. The effect of vitamin D...

We don't know what the mechanism is. The effect of vitamin D on bones is well recognized, but vitamin D can also influence the growth of other types of cells in the body and the formation of connective tissue by other types of cells in the body. The tissues in the lung undergo a process of renewal and remodeling throughout life, and it is conceivable that vitamin D may influence this, but further work is necessary to find out if this is the case.