Vitamin D is a fat-soluble vitamin, as it is stored in the liver and fatty tissues. It is stored for long periods and is eliminated slowly from the body. Vitamin D is often referred to as the “sunshine vitamin” because the body makes it after being exposed to sunshine. It is the only vitamin that the body can produce on its own, but it needs sunlight to do so. The body must get all other vitamins from diet and/or supplementation. There are several forms of Vitamin D, including D2 and D3. Vitamin D2 is synthesized by plants, and Vitamin D3 is synthesized by humans when their skin is exposed to ultraviolet-B (UVB) rays from sunlight.