Vitamin A: Sources, RDA, Functions, and Deficiency

Vitamin A

A fat soluble vitamin whose active form is present only in animal tissues and whose pro-vitamin, beta carotene, is present in plant tissues.

Retinoids

A term referring to all compounds with vitamin A activity.

Retinol

The alcohol form of Vitamin A.

Retinal

The aldehyde form of Vitamin A which combines with opsin to form rhodopsin.

Retinoic acid

The acid form of Vitamin A; it acts as a key hormone-like growth factor for epithelial cells and other cell types.

Beta carotene

A pro-vitamin present in plant tissues (e.g., carrots, papaya, mango) that acts as an antioxidant.

Animal sources of Vitamin A

Milk, butter, cream, cheese, egg yolk, liver, and fish liver oils.

Plant sources of Vitamin A

Carrot, Papaya, mango, pumpkins, and green leafy vegetables like spinach and amaranth.

RDA for Children

$$400-600\,\mu g/day$$

RDA for Men

$$750-1000\,\mu g/day$$

RDA for Women

$$750\,\mu g/day$$

RDA for Pregnancy

$$1000\,\mu g/day$$

Rhodopsin

An essential light-absorbing molecule ($11\text{-cis-retinal-opsin}$) needed for color vision and seeing in dim light.

Wald's visual cycle

The biochemical