Vitamin D3 is an active antirachitic factor. Vitamin D promotes intestinal absorption of calcium and phosphates, transport of mineral salts and calcification of bones, as well as regulates the excretion of calcium and phosphates by the kidneys.   Vitamin D3 ensures the normal functioning of bones and teeth, as well as supports the normal function of the immune system and muscles.   In addition, vitamin D3 plays a role in cell division and maintaining a normal concentration of calcium in the blood.