Academic journal article Research Quarterly for Exercise and Sport

Physical Activity as a Natural Antioxidant Booster and Its Effect on a Healthy Life Span

Academic journal article Research Quarterly for Exercise and Sport

Physical Activity as a Natural Antioxidant Booster and Its Effect on a Healthy Life Span

Article excerpt

The first of three broad goals of Healthy People 2000: National Health Promotion and Disease Prevention Objectives (U.S. Public Health Service, 1991) is to improve the healthy life span of all Americans (Mason & McGinnis, 1990). Several studies have established that regular physical activity contributes to good health and longevity (Morris et al., 1953; Paffenbarger, Wing, & Hyde, 1978; Blair, 1989). It is no coincidence that many objectives supporting the goals of Healthy People 2000 and the Surgeon General's report on physical activity and health (U.S. Department of Health and Human Services, 1996) include promoting physical activity and reducing sedentary behaviors. The ways regular physical activity impact health and longevity have, in the past, focused on improved cardiovascular health (Caspersen, 1987) and, recently, on decreased cancer risk (Lee, 1995). Another explanation for a healthy life span associated with physical activity may be related to antioxidant status.

By definition, an antioxidant is any substance that prevents the oxidation of lipids, carbohydrates, proteins, DNA, and other oxidizable substrates (Halliwell, 1990). In effect, this means that antioxidants protect lipids, carbohydrates, proteins, and DNA. Many enzymatic (e.g., superoxide dismutase, catalase) and nonenzymatic (e.g., Vitamin E, C, beta-carotene, glutathione, ubiquinol-10) substances act as antioxidants. Those having primary physiological importance are superoxide dismutase, catalase, and the glutathione system. Antioxidant systems such as Vitamin E, C, and glutathione (GSH) act synergistically with a variety of compounds to remove radical molecules or interrupt radical reactions.

The role of antioxidant activity in health has gained attention partly because of the mass marketing of antioxidant supplements purporting to have antiaging effects. Several informative reviews on exercise and antioxidants have been published recently (Jenkins, 1993; Ji, 1995; Sen, 1995; Kanter, 1994). These reviews have carefully explained the biochemistry of oxygen toxicity during exercise. Most have focused on nutritional modification or supplements that may enhance antioxidant status. This paper is intended for health and physical education professionals for whom physical activity is a mainstay both in and out of the work setting. The purpose of this paper is to summarize findings from studies over the past two decades that have focused on life span, health, antioxidants, and the effectiveness of physical activity as a natural antioxidant booster.

What Are Antioxidants and How Do They Contribute to Health and Longevity?

Atoms and molecules usually contain in their outer valence shells paired electrons which circle around the molecule and contribute to its stability. Free radicals are unstable molecules with an unpaired electron in their outer shells. It is estimated that 1 of every 25 oxygen molecules used for metabolism can result in an unstable form of oxygen called superoxide radical ([O.sub.[2.sup.*]]; McCord & Fridovich, 1969). This can occur during oxidative phosphorylation when oxygen is reduced to water, one electron at a time. An electron can escape at the ubiquinone step, resulting in an unpaired electron in oxygen's outer shell. Therefore, in the case when oxygen is not completely reduced to water by the transfer of four hydrogens and four electrons, an [O.sub.[2.sup.*]] or some other reactive oxygen species (ROS) may be created instead. To restore stability, [O.sub.[2.sup.*]] vigorously seeks to strip an electron from a hydrogen contained within all types of cell sources. [O.sub.[2.sup.*]] attacks sugars, proteins, DNA, polyunsaturated fatty acids, and other biological molecules for an electron to pair up with the lone one in its outer shell. ROS is a general term often used to describe oxygen-centered radicals such as [O.sub.[2.sup.*]] and hydroxyl radical (*OH), and some nonradical derivatives of oxygen, such as hydrogen peroxide, hypochlorous acid, and ozone. …

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