Evidence-based non-skeletal actions of vitamin D.

Vitamin D is a major regulator of mineral homeostasis through its action in the kidney, intestine, bone and parathyroid glands. On these tissues, its active form, calcitriol, acts by binding to a specific nuclear receptor that belongs to the steroid/thyroid hormone receptor family. This receptor, however, has also been identified in several additional human tissues. So, apart from its traditional actions related to calcium, vitamin D and its synthetic analogs are being increasingly recognized for their anti-proliferative, pro-differentiative and immunomodulatory activities. Low levels of vitamin D have been linked to many chronic diseases. Decreased muscle function and increased fall risk in elderly people; prostate, breast and colorectal cancers; diabetes mellitus; and other health problems have been associated to low circulating levels of 25-hydroxyvitamin D. This paper presents an overview of the available scientific evidence for the non-calcemic actions of vitamin D in humans.