Vitamin A

Vitamin A is responsible for the normal structure and function of skin and the lining of the digestive system and lungs. Maintaining healthy skin/linings helps prevent invasion of bacteria and viruses into the body, which assists the body’s immune system. Vitamin A is also involved in cell differentiation, including normal cell growth and development, vision and the immune system.

There are two forms of Vitamin A, retinol which is found in animal sources and carotenoids (beta carotene) from plant sources. Beta carotene can be converted to retinol in the body.

Recommended daily intakes (RDI) for Vitamin A (mg/day)

 

Age (years)

 

19+ years

Women

750 µg

Men

750 µg

NB: Retinol equivalents. 6mg beta carotene = 1mg retinol

Vitamin A status depends on the adequacy of the Vitamin A stores (90% stored in the liver) and protein (carriers). If a person stops consuming foods containing Vitamin A, signs of deficiency will not appear until all of the stores are depleted.

Vitamin A deficiency

Vitamin A deficiency is the developing world’s major nutrition problem, but is very rarely seen in Western countries. One of the symptoms is night blindness, in which a person will lose the ability to recover promptly from a temporary blinding when a flash of bright light occurs at night or when a light goes out. In serious cases of deficiency this leads to blindness.

Vitamin A toxicity

High levels of retinol in a pregnant woman’s diet have been linked to an increase risk of birth defects. Pregnant women should avoid taking high doses of Vitamin A unless as advised by a medical professional.

Acne medicine is made from Vitamin A but is chemically very different. Vitamin A itself has no beneficial effect on acne, and therefore taking supplements for the prevention or healing of acne is of no benefit.

Food sources of Vitamin A

Sources of Retinol include liver, whole milk, cheese and butter. Good sources of carotenes are milk, carrots, dark green leafy vegetables and orange coloured fruits. The intake of carotenes is strongly related to the amount of fruit and vegetables consumed. People should be encouraged to eat brightly coloured – yellow, orange, red and green – fruits and vegetables as these are the richest in Vitamin A compounds.