The Aesthetics Advisor

What Is Vitamin D? Vitamin D is a fat-soluble vitamin, meaning that it dissolves in fats and oils and can be stored in your body for a long time. Two main dietary forms exist ( Trusted Source ): Vitamin D3 (cholecalciferol). Found in some animal foods, like fatty fish and egg yolks. Vitamin D2 (ergocalciferol). Found in some plants, mushrooms, and yeasts. Of the two, D3 (cholecalciferol) seems to be almost twice as effective at increasing blood levels of vitamin D as D2 (ergocalciferol) ( Trusted Source ,  Trusted Source ). What Does It Do in Your Body? Vitamin D needs to undergo two conversion steps to become active ( Trusted Source ,  Trusted Source ). First, it is converted to calcidiol, or 25(OH)D, in your liver. This is the storage form of the vitamin. Second, it is converted to calcitriol, or 1,25(OH)2D, mostly in your kidneys. This is the active, steroid-hormone form of vitamin D. Calcitriol interacts with the vitamin D receptor (VDR), which is found in almost every single cell