Vitamin D
Vitamin D is a group of fat-soluble pro-hormones consisting of 5 different vitamins: vitamin D1, D2, D3, D4 and D5. The two most important forms in which vitamin D can be found are vitamin D2 and vitamin D3, both of which have very similar biological activity. Vitamin D2 is of plant origin, while D3, derived from cholesterol, is synthesized in animal organisms. The main source of vitamin D for the human body is exposure to solar radiation. Vitamin D is not...