Vitamin D is a fat-soluble vitamin. There are two major forms of vitamin D: D2 (ergocalciferol) and D3 (cholecalciferol). D3 is produced naturally in human skin when expose to ultraviolet B light and more efficient at raising 25-hydroxyvitamin D levels than D2. Major cause of vitamin D3 deficiency is inadequate sun exposure. Many people avoid the sun for fear of harmful UV rays. Other factors include the use of sunscreen, protective clothing, having dark skin, and age may also prevent getting enough vitamin D from the sun. It is well-known and established that vitamin D is necessary for supporting strong bones, teeth and immune function. More recent studies established that vitamin D is an essential nutrient for cardiovascular health, regulating mood, reduce anxiety and depression.