Vitamin D is known as the sunshine vitamin, because a chemical reaction of the sun’s ultraviolet rays on the skin produces vitamin D-3. Food sources to obtain vitamin D are almost exclusively reserved to oily fish such as herring or salmon, small amounts are also found in foods such as creamy milk and the yolks of eggs.Vitamin D is a fat-soluble vitamin, which is absorbed with the fats in the diet through the intestinal wall. The main function of vitamin D is to maintain normal blood levels of calcium and phosphorus. By promoting calcium absorption, vitamin D helps to form and maintain strong bones.