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Vitamin E: Nature’s Antioxidant
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The chemical definition of oxidation is that part of an oxidation-reduction reaction characterized by electron loss or by an algebraic increase in oxidation number. In practical terms, oxidation can be seen as the rusting of iron, the rancidity of fats and oils, or perhaps even human aging. The oxidation that occurs in the body is seen in the aging process; however, it can also lead to the development of degenerative diseases. The oxidation of food occurs when oxygen is added to unsaturated sites of organic molecules. Oxygen, light, heat, heavy metals, pigments, and alkaline conditions are catalysts in this process. Oxidation can be slowed down by the addition of antioxidants.
Antioxidants are defined as chemicals that specifically retard deterioration, rancidity, or discolouration due to oxidation. The use of antioxidants prevents or minimizes the phenomenon of oxidation in foods. There are two classes of antioxidants: metal sequestrants and free-radical scavengers. Metal sequestrants precipitate a metal or suppress its reactivity by occupying all coordination sites. Free-radical scavengers include butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), the tocopherols (vitamin E), and ascorbic acid (vitamin C).
Oxidation in the body usually occurs via naturally-produced free radicals. Radicals are compounds which contain one or more unpaired electrons and consequently are unstable. To achieve stability, free radicals "borrow" or "steal" electrons from stable compounds. Consequently, the formerly stable compounds become reactive and oxidation occurs. The result is the formation of a chain reaction. One of the ways the body controls oxidation is with vitamin E.
Vitamins E is a natural antioxidant and is often used to denote any mixture of biologically active tocopherols. There are four forms of tocopherols found naturally in vitamin E of which alpha-tocopherol is the most active. Vitamin E is fat soluble and therefore acts as an antioxidant in the lipid part of the cells. When lipids undergo oxidation they form peroxide radicals which are highly reactive. Vitamin E slows this process by donating one of its hydrogen atoms to the peroxide radical which then becomes stable and unreactive. As a result, the vitamin E becomes an unreactive free radical.
Dr. Keith Ingold at the National Research Council’s (NRC) Steacie Institute for Molecular Sciences in Ottawa, Ontario, is the world’s foremost researcher in the chemistry of vitamin E potency. Dr. Ingold is a physical organic chemist who studies reactions involving free radicals and is particularly interested in why vitamin E is so efficient at trapping radicals. Ingold is also interested in other chemically reactive intermediates where the major emphasis is on the fundamental studies of simplified systems which are used to develop and test concepts and techniques applicable to problems in environmental science, biology, and medicine. Some of the biological systems that Ingold is studying are the mechanism for atherosclerosis (the hardening of the arteries) and the detection of nitric oxide in vivo. Ingold is working with Australia’s Heart Research Institute to determine if atherosclerosis is initiated by the oxidation of a low density lipoprotein that carries fat around the human body. Nitric oxide, a radical found in vehicle exhaust, has been revealed to be a major signalling molecule in the human body and has many functions such as relaxing the blood vessels to control blood pressure.
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