[ Vitamin D, D2, D3 ]
Vitamin D is any of a group of fat-soluble nutrients that are essential for the absorption of calcium, magnesium and phosphate. While referred to as a vitamin, chemically vitamin D is a steroid with important metabolic, signalling and immune system functions.
The name Vitamin D (without a subscript) can refer to either of the two major forms, vitamin D2 (ergocalciferol) or vitamin D3 (cholecalciferol).
The major natural source or vitamin D is exposure to UVB radiation of the sun via the skin. Dietary sources of vitamin D include fish oil and foods fortified with the vitamin, including cow’s milk and eggs.