Protean manifestations of vitamin D deficiency, part 2: deficiency and its association with autoimmune disease, cancer, infection, asthma, dermopathies, insulin resistance, and type 2 diabetes.

Vitamin D deficiency is epidemic and its manifestations are protean. Vitamin D deficiency is associated with autoimmune diseases (particularly multiple sclerosis and type 1 diabetes) and has been associated with infection, allergy, asthma, and dermopathies (particularly psoriasis). Asthma may be worsened by vitamin D deficiency and correction of the deficiency has been shown to improve the manifestations of asthma. Vitamin D deficiency has been associated with multiple cancers, including those of the breast, colon, ovary, and prostate. Due mainly to increased insulin resistance but also to an impairment in insulin release, vitamin D deficiency is associated with the development of type 2 diabetes. In addition, the complications of diabetes may be worsened by vitamin D deficiency.