VITAMIN A

Vitamin A (retinoid) is a fat-soluble vitamin found

mainly in animal foods in the vitamin form and in plant

foods primarily as carotenes, substances that are formed

into vitamin A chiefly in the small intestine.

Function: Essential for growth and for keeping skin

and other tissues healthy; helps eyes to adapt to dim light

and perceive colors; essential for normal tooth

development.

Sources: Beef, chicken and pork livers; whole and

vitamin A-fortified milk; cheddar cheese; butter;

margarine; egg yolk; deep green, yellow or orange

vegetables and fruits (including carrots, spinach,

collards, broccoli, kale, nectarines, apricots, mangoes,

cantaloupe, pumpkins, winter squash, turnip greens, sweet

potatoes, and watermelon).

Deficiency: Vitamin A deficiency is reare in the

United States; it mainly occurs among some people in

developing countries. Some signs include skin changes,

stunted growth, night blindness, and serious eye problems

(such as drying, thickening, wrinkling, and muddy

pigmentation of the mucous membrane lining the eyelid and

eyeball, which eventually can destroy the eye). Inadequate

intakes of foods containing vitamin A have been associated

with some types of cancer, but the effect, if any, appears

related to lack of carotene.

Excess: Because vitamin A is fat soluble, it is stored

in the body. As a result, continued high doses (several

times the U.S. RDA) have toxic effects. Signs of toxicity

include dry and itching skin, headaches, and nausea and

diarrhea. High vitamin A intake during pregnancy also may

cause birth defects, but it is not known at what level this

can occur. Excessive amounts of carotene are not known to

be toxic, but will cause the skin to turn deep yellow. The

color disappears when the amount of carotene in the diet is

decreased.