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Free-radical theory of aging

The free radical theory of aging (FRTA) states that organisms age because cells accumulate free radical damage over time. A free radical is any atom or molecule that has a single unpaired electron in an outer shell. While a few free radicals such as melanin are not chemically reactive, most biologically-relevant free radicals are highly reactive. For most biological structures, free radical damage is closely associated with oxidative damage. Antioxidants are reducing agents, and limit oxidative damage to biological structures by passivating them from free radicals.

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The Free Radical Theory of Aging With age comes increasing and sometimes cumulative exposure to both natural and synthetic environmental toxins, from heavy metals and pesticides to tobacco smoke and radiation--even life-giving oxygen can be harmful. Much of the damage from these exposures results from the generation of free radicals. These extremely reactive molecules or fragments of molecules have unpaired, or "free," electrons that in the normal course of metabolism are channeled into energy production. In some cells they may be used to kill viruses and bacteria. But because of their extremely high energy and inexorable search for another electron, they can also damage normal tissues if too many are produced or are not adequately controlled. The prematurely aged, wrinkled skin of smokers is caused by the free radical-induced damage that smoking engenders. In fact, smoking is probably the greatest source of voluntary exposure to free radicals. Free radicals disrupt the normal production of DNA and RNA and alter the lipids, or fats, in cell membranes. They also damage cells lining blood vessels and interfere with the production of prostaglandins, which are derived from essential fatty acids and regulate many physiological functions. Partly as a result of free radical damage, aging leads to alteration of proteins (cross-linking). Proteins are complex chains of amino acids that bend into three-dimensional structures. Cross-linking takes place when attachments are formed along the chain in abnormal places, disrupting the protein's function. This leads to poor cell membrane performance in molecular transport, decreased enzyme activity, and inhibition of immune function.1 The total effect is a variable rate of decline depending on the level of exposure to free radicals. Oxygen derivatives are involved in most free radical reactions. In a sense, the aging process could be viewed as one of gradual oxidation, or in physical chemistry terms--rusting. Although free radicals are usually associated with excessive oxygen and oxidation, in the right concentrations oxygen can reduce free radical damage.2 Oxygen free radicals include hydroxyl and superoxide, while activated oxygen species (those that react readily and trigger free radical production) include singlet oxygen and peroxide. Natural Protection The body produces essential antioxidant defenses internally. Enzymes that control free radicals include superoxide dismutase, glutathione peroxidase, and catalase, as well as other molecules such as cholesterol, steroid hormones and sulfur-containing amino acids that neutralize free radicals. It is also possible to choose many nutrients in both foods and supplements that help fight free radicals. Most free radical protection involves eating a better diet, exercising, maintaining a clean environment both internally and externally, and reducing stress, in addition to taking dietary supplements. Eating better means eating whole, organic foods whenever possible and avoiding processed foods and artificial chemicals used for preservation, coloring and flavoring. Exercising increases production of free radical-scavenging enzymes, which protect the body from the increased oxygen-related stress associated with a higher respiratory rate. A clean environment means avoiding excessive exposures to toxic air pollution, chemicals such as solvents and industrial waste that leach into water supplies, harsh cleaning and cosmetic chemicals, heavy metals, unnecessary medications, and pesticides. Pesticides can generate free radicals, and many also mimic hormones and can disrupt the normal hormonal balance. Stress increases the metabolic rate and alters hormonal balance, which also generates free radicals.

Contributed by Lily Barkin

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