<unk>  is a group of fat-soluble prohormones, the two major forms of which are<unk> 2 (or ergocalciferol) and<unk> 3 (or cholecalciferol). The term<unk>  also refers to metabolites and other analogues of these substances.<unk> 3 is produced in skin exposed to sunlight, specifically ultraviolet B radiation.<unk>  plays an important role in the maintenance of organ systems.<unk>  regulates the calcium and phosphorus levels in the blood by promoting their absorption from food in the intestines, and by promoting re-absorption of calcium in the kidneys.
It promotes bone formation and mineralization and is essential in the development of an intact and strong skeleton.
It inhibits parathyroid hormone secretion from the parathyroid gland.<unk>  affects the immune system by promoting immunosuppression, phagocytosis, and anti-tumor activity.<unk>  deficiency can result from inadequate intake coupled with inadequate sunlight exposure, disorders that limit its absorption, conditions that impair conversion of<unk>  into active metabolites, such as liver or kidney disorders, or, rarely, by a number of hereditary disorders. Deficiency results in impaired bone mineralization, and leads to bone softening diseases, rickets in children and osteomalacia in adults, and possibly contributes to osteoporosis.<unk>  deficiency may also be linked to many forms of cancer.
Vitamin D
Vitamin C
Vitamin A
Tocopherol
Iron
Thiol
Folic acid 
Thiamin