Vitamin D is a group of fat-soluble
prohormones, the two major forms of which are vitamin D
2 (or
ergocalciferol) and vitamin D
3 (or
cholecalciferol).
[1] The term vitamin D also refers to
metabolites and other analogues of these substances. Vitamin D
3 is produced in skin exposed to sunlight, specifically
ultraviolet B radiation.
Vitamin D plays an important role in the maintenance of organ systems.[2]
Vitamin D deficiency can result from inadequate intake coupled with inadequate sunlight exposure, disorders that limit its absorption, conditions that impair conversion of vitamin D into active metabolites, such as liver or kidney disorders, or, rarely, by a number of hereditary disorders.[2] Deficiency results in impaired bone mineralization, and leads to bone softening diseases, rickets in children and osteomalacia in adults, and possibly contributes to osteoporosis. Research has indicated that vitamin D deficiency is linked to colon cancer and more recently, to breast cancer[3]. Conflicting evidence links vitamin D deficiency to other forms of cancer. Low levels of vitamin D appear to be associated with higher risk of heart attack in men, according to a report in the June 9, 2008 issue of Archives of Internal Medicine.[4]
Several forms (vitamers) of vitamin D have been discovered. The two major forms are vitamin D2 or ergocalciferol, and vitamin D3 or cholecalciferol.
