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Beta carotene is one of the most important naturally occurring antioxidants. It is a fat-soluble pigment found in plants (notably carrots and many colorful vegetables and fruits) and in the sea alga Dunaleilla salina and D. bardawil. Naturalbeta carotene supplements are derived primarily from D. salina. Beta carotene is one of the major dietary carotenoids and one of the most biologically active of approximately 800 carotenes and more than 1,000 carotenoids present in food. It is responsible for the orange or yellow colors of many fruits and vegetables. In the human body, beta carotene is found in lipids and in fat tissues. Sometimes beta carotene is called provitamin A because it is more easily converted to vitamin A (retinol) in the liver than other carotenoids. Beta carotene is considered to be a conditionally essential nutrient because it becomes essential when vitamin A intake is low.
Beta carotene consists of a chain of 40 carbon atoms, with conjugated double bonds and a ring structure at each end of the chain. Depending on the positions of the molecular groups attached to the carbon chain, naturally occurring beta carotene may be:
Synthetic beta carotene is primarily all-trans.
In plants and alga, beta carotene and other carotenoids attract light for photosynthesis and provide protection from toxic forms of oxygen. Beta carotene is a powerful antioxidant because it destroys toxic free radicals, including singlet oxygen—an oxygen atom that is missing an electron and is very damaging to human tissue if not taken up quickly and "deactivated."
Vitamin A is obtained in the diet from animal products or is made in the liver from beta carotene and other carotenoids. Vitamin A is essential for:
In sub-Saharan Africa about three million children under the age of five suffer from an eye disorder, caused by vitamin-A deficiency, that can lead to blindness and death. Although red palm oil, a traditional African food, contains high provitamin A, its substitution by imported cooking oils has reduced this dietary source in many homes. Many vegetables and fruits also contain provitamin A, but are not always consumed in adequate amounts. Vitamin A deficiency is the leading cause of blindness worldwide.
In the 1920s vitamin-A deficiency was linked to stomach cancer and to precancerous conditions in the epithelial (lining) cells of the throat and lungs. In 1977 vitamin A supplementation was shown to inhibit certain cancers and to reduce the growth of certain tumors in atrisk animals.
Author Info: Margaret Alic, The Gale Group Inc., Gale, Detroit, Gale Encyclopedia of Alternative Medicine, 2005
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