Vitamin D is the general name given to a group of fat-soluble compounds that are essential for maintaining the mineral balance in the body.
The main forms are vitamin D2 and vitamin D3. In nature only a few foods contain vitamin D, such as fatty fish, liver and egg yolks.
Vitamin D is a generic term of all steroids including vitamin D3 and vitamin D2. Vitamin D3, also known as cholecalciferol, and D2, known as ergocalciferol.
Vitamin D3, is the primary form of the vitamin encountered in zoologic species; it is stored in a number of tissues, including the liver and skin. Fish liver oils are a rich natural source of this material.
Vitamin D3, produced in the skin of humans and animals by the action of sunlight (ultraviolet light 290 to 320 nm) on its precursor molecule, the cholesterol derivative 7-dehydrocholesterol (a normal metabolite of cholesterol found in the skin). Absorption of light energy induces breakage of the 9, 10 carbon bond; a spontaneous isomerization (shifting of double bonds) then occurs. It is said to be more bioactive.
Ergocalciferol, or vitamin D2, is derived from ergosterol, a plant steroid and only enters the body via the diet, from consumption of foods such as oily fish, egg yolk and liver. It is the form of this vitamin normally used to fortify such foods as milk, bread, and cereals.
Vitamin D is absorbed from the diet in the intestinal tract in association with liquids and the presence of the bile slats. Once in the liver, one metabolite 25 hydroxy-vitamin D3 is formed, which is a about four times as active as vitamin D.
Vitamin D (D3 and D2) in physiologic replacement and pharmacologic doses has been used to correct vitamin D depletion in the elderly and to prevent vitamin D deficiency at all ages.
Vitamin D (D3 and D2)
