previtamin

Previtamin D is an intermediate in the production of vitamin D.

The term "previtamin" is a synonym.

Vitamin A The possible anticancer benefits of vitamin A, its previtamin, beta-carotene, and its chemical relatives called retinoids have been suspected for decades.

Following this, the previtamin D undergoes a [1,7] antarafacial sigmatropic rearrangement and therein finally isomerizes to form vitamin D.

An antarafacial [1,7] shift is observed in the conversion of lumisterol to vitamin D, where following an electrocyclic ring opening to previtamin D, a methyl hydrogen shifts.

Although sunscreens could almost entirely block the solar induced production of cutaneous previtamin D3 on theoretical grounds or if administered under strictly controlled conditions, in practice they have not been shown to do so.

Those hoping to reduce their risk of cancer through supplements of vitamin A or its previtamin, beta-carotene, should know that the evidence for cancer prevention in people is based on eating foods rich in beta-carotene, not on taking supplements.

People living in latitudes far from the equator developed light skin in order to help absorb more vitamin D. People with light (type II) skin can produce previtamin D3 in their skin at rates 5-10 times faster than dark-skinned (type V) people.