Human Nutrition 3(3+0)
Lesson 21 : Vitamin D


Vitamin D is a fat-soluble vitamin that is essential for maintaining normal calcium metabolism. It plays a critical role in the body’s use of calcium and phosphorous. It increases the amount of calcium absorbed from the small intestine and helps in formation and maintenance of bones. Children especially need adequate amounts of vitamin D to develop strong bones and healthy teeth.

Vitamin D is used in dietary supplements in two forms:


  • Ergocalciferol is considered a vegetarian source of vitamin D. Plants synthesize ergosterol, which is converted to vitamin D2 (ergocalciferol) by ultraviolet light.

  • Cholecalciferol, the D3 form of the vitamin, can be obtained from animal or microbial sources. Vitamin D3 (cholecalciferol) can be synthesized by humans in the skin on exposure to ultraviolet-B (UVB) radiation from sunlight, or it can be obtained from the diet.

Vitamin D2 is less active than vitamin D3.

Last modified: Thursday, 9 February 2012, 9:37 AM