Antioxidant: an agent that inhibits oxidation; any number of chemical substances including certain natural body products and nutrients that can neutralize the oxidant effect of free radicals and other substances.
Free radicals, formed in the course of normal cellular respiration and metabolism, and more abundantly under the influence of certain environmental chemicals and sunlight, have been inculpated in various types of tissue damage, particularly those involved in atherosclerosis, the aging process, and the development of cancers.
A free radical is any atom or molecule that has 1 or more unpaired electrons and is therefore highly reactive; seeking to acquire electrons from other substances. Free radicals are normally scavenged from tissues by the antioxidant enzymes, super-oxide dismutase and glutathione peroxidase. Ubidecarenone (coenzyme Q10) is also thought to act as an antioxidant in mitochondrial respiration reactions. In addition, a number of nutrient substances, vitamins, and minerals have been shown to contribute to antioxidant functions, generally by serving as co-factors or coenzymes. These include selenium beta-carotene, vitamin C, and vitamin E.
It has been postulated that an imbalance between the production of free radicals and natural antioxidant processes may be a major causative factor in aging and in many chronic and degenerative disorders. Some researchers have speculated that antioxidant nutrients may have a role in disease prevention as well.
Oxidation of low-density lipoprotein cholesterol does indeed seem to be responsible for foam cell formation in the genesis of antherosclerotic plaques. In addition, free radicals have been shown to damage DNA in ways that can culminate in malignant change. Oxidations also occur in many beneficial processes, however, including chemotaxis of cells with immunologic functions, phagocytosis, clotting mechanisms, and apoptosis.
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