Vitamin A

Also known as retinol

Functions

Used in photochemical reactions within the eye to aid light perception in rods. Also thought to help prevent cancer, along with its precursor beta-carotene. Helps prevent night-blindness and defective eyesight. Vitamin A is essential for healthy development of a fetus and young children. It protects the hair and skin and dictates the condition of mucous membranes. Beta-carotene helps protect the body from harmful effects of excessive sunlight. Beta-carotene is an important antioxidant used in foods, not least because the best antioxidant, vitamin C is very sensitive to conditions, and can easily be destroyed by heat, light or oxygen.

Sources

Vitamin A itself is only present in animal products. However its many precursor including retinal, retinoids, carotene and carotinoids can be found in yellow and orange vegetables such as carrots, squashes, and sweet potatoes as well as animal fats, egg white, fish and some green vegetables. Once adsorbed by the body, they are easily converted.

Requirements

Recommended Daily Amount:   5000 IU (international units), about 1mg. The actual amounts required depend on which precursors are present in your food. Vitamin A is absorbed in the small intestine with fats, and so its uptake can be affected by diarrhoea. It is stored in the liver, so hepatic diseases can affect its processing.

Related diseases

A deficiency in vitamin A leads to Xerophthalmia, a disease which causes drying and degeneration of the cornea and leads to blindness. Minor deficiencies can lead to nightblindness.