Vitamin D: hero or hype.

In recent years, vitamin D deficiency has been implicated, by predominantly observational studies, in a wide variety of ailments including skeletal disease, cardiovascular disease, cancer, diabetes, mental and neurologic disorders, and various etiologies of adverse pregnancy outcome. The following is a review of the physiology of vitamin D, clinical signs and symptoms of inadequate and excessive vitamin D, and the literature purporting its many presumed health benefits.