B I N A R A G A . I N F O

Vitamin A

Vitamin A is a fat-soluable vitamin which means that it is absorbed with the aid of fats and stored in the liver and body fat until needed. Body stores can last years. In nature it occurs in two forms; retinol and carotene. Retinol, its true form, is found in animal foods and by-products such as liver and fish liver oils. Carotene, a precursor of the actual vitamin, is found in yellow vegetables and fruits, and green leafy vegetables. Carotene is not directly used by the body, but converted into retinol with the aid of bile and fats. Vitamin A is needed to keep the mucous membranes which line the nose, throat, lungs, digestive tract and bladder healthy; to maintain normal vision (especially for seeing in low-light); for healthy skin, and for the proper formation of bones and teeth.

Deficiencies of vitamin A are relatively rare in Western countries, but it is common in Third World countries, where it is the major cause of childhood blindness. Signs of vitamin A deficiency include night blindness, reduced resistance to infection, reduced growth in children, red itchy eyes, kidney stones, and sensitivity to bright lights. Severe deficiencies can lead to blindness.

Since vitamin A is stored in the body, it can be dangerous to take regular supplements in excess of the body's needs. Symptoms of toxicity include blurred vision, headaches, fatigue, insomnia, joint pains, loss of appetite, and menstral irregularities. In severe cases it can lead to liver, brain, and nervous system damage. If consumed in large amounts during the first few months of pregnancy it can cause birth defects.

The unit used to measure vitamin A is the retinol equivalent (RE) or the internal unit (IU). From animal sources one RE is equal to three and a half IU, and from plant sources (beta carotene) one RE is equal to ten IU. No adult should ever consume daily more than 10,000 IU of vitamin A (from all sources); no newly pregnant woman (first trimester) should ever consume daily more than a total of 8,000 IU (from all sources); and no children should ever take any vitamin A supplements (including fish liver oils) unless prescribed by a doctor. Beta-carotene has not been shown to cause short-term toxicity, though consuming excessive amounts of carotene-rich foods like carrot juice may make your skin turn yellow.

Good sources of vitamin A include liver, egg yolks, butter, cheese, chicken, whole-milk, margarine, carrots and carrot juice, sweet potato, pumpkin, squash, spinach, broccoli, apricots, peaches, and rockmelon. Little vitamin A is lost with normal cooking temperatures, freezing, or canning; but allowing vegetables that are normally high in vitamin A to wilt or dry out before cooking them, rapidly lowers their vitamin A content.