Vitamin D Overview

A "vitamin" by definition is a substance regularly required by the body in small amounts but which the body cannot make and is, therefore, required to be supplied in the daily diet. Technically the molecular species classified as vitamin D is not really a vitamin because it can be produced by exposure of the skin to sunlight. However, for nutritional and public health reasons, vitamin D continues to be classified officially as a vitamin.

Types: There are two chemical forms of vitamin D, namely vitamin D2 (sometimes referred to as ergocalciferol) and vitamin D3 (sometimes referred to a cholecalciferol). The natural form of vitamin D for animals and man is vitamin D3 that is produced in their bodies from cholesterol and 7-dehydrocholesterol. An alternative vitamin D2 is derived from the yeast sterol ergosterol by chemical procedures.

Importance: Vitamin D3 is essential for life in higher animals. Classically vitamin D3 has been shown to be one of the most important biological regulators of calcium metabolism through stimulating the absorption of calcium from food across the intestine and participating in the incorporation of the absorbed calcium in to the skeleton.