What Is Cholecalciferol? Cholecalciferol, also known as Vitamin D3, is a type of Vitamin D that is produced by the skin when exposed to sunlight. Because the body produces it, Vitamin D3 is not a true vitamin, but it is usually considered a vitamin due to its importance in the human body. Cholecalciferol Benefits † Cholecalciferol may help fortify the bones, promote heart health, and support immune function. Cholecalciferol may also aid cognitive function, promote healthy mood, and support brain function. Fortify the bones Helps protect against sun damage and fight signs of aging along with regular sunblock usage Support heart health and immune function Aid cognitive and mental function Improve muscle mass Aid weight loss Works in maintaining a healthy mood Supports healthy hair, skin, and nails Reduce muscle and joint pain Increases testosterone