All-D (Cholecalciferol) is one of the five forms of vitamin D. Cholecalciferol is synthesized in the skin from 7-dehydrocholesterol under the action of ultraviolet B (UVB) radiation from sunlight depending on the intensity of the UVB in the sunlight – determined by latitude, season, cloud cover, and altitude – and the age and degree of pigmentation of the skin. Vitamin D is important for the absorption of calcium and for the functioning of calcium in the body.
