Vitamin D is necessary for providing the body in calcium and phosphorus. This explains its second name: holikaltsiferol or carrying calcium. Vitamin D promotes absorption of calcium and phosphorus in the intestine and, because of it, is an essential nutrient for the formation and maintenance of bone mass. In addition, vitamin D plays an important role in maintaining the immune system. Vitamin D is synthesized in the skin under the sun, but it was recently revealed, that about half of the world population suffers from deficiency of this essential nutrient. Vitamin D deficiency is very dangerous and lead to rickets, osteomalacia and osteoporosis.