Which of the following vitamin is NOT required from diet?
Vitamin D is synthesized in the skin. 7-Dehydrocholesterol (an intermediate in the synthesis of cholesterol that accumulates in the skin) undergoes a nonenzymic reaction on exposure to ultraviolet light, yielding previtamin D. This undergoes a fuher reaction over a period of hours to form cholecalciferol, which is absorbed into the bloodstream. Only when sunlight exposure is inadequate is a dietary source required. Most of its actions are mediated by way of nuclear receptors that regulate gene expression. It also has a role in regulating cell proliferation and differentiation. Ref: Bender D.A. (2011). Chapter 44. Micronutrients: Vitamins & Minerals. In D.A. Bender, K.M. Botham, P.A. Weil, P.J. Kennelly, R.K. Murray, V.W. Rodwell (Eds), Harper's Illustrated Biochemistry, 29e.
Nicotinic acid
Ascorbic acid
Vitamin-A
Vitamin-D