Exercise: activity that requires physical or mental exertion, especially when performed to develop or maintain fitness (Halliwell and Whiteman, 2004). Exercise requires the body perform physical work, which in turn causes increased levels of oxygen.
As oxygen enters the body and is processed, oxygen free radicals are created. Free radical levels in exercising individuals can be up to three times the levels of non-exercising individuals.
Oxidation is defined as the addition of oxygen to a compound which results in a loss of electrons (Halliwell and Whiteman, 2004). Free radicals are compounds that have lost an electron, and they damage cells in the body through a chain reaction. An oxygen free radical will, in the presence of an absent electron, steal another molecule's electron. In turn, the "victimized" molecule must steal another electron from another molecule, and the chain moves on.
setting off a ripple effect of free radical formation called
lipid peroxidation,which eventually leads to
damage of the cell" (ABC Bodybuilding, 2004).
DNA damage is onset by common oxidants such as oxygen and lipid peroxidation (Kim et al., 2001).
Common belief suggests that oxygen free radicals play a role in the development of many diseases and age-related disorders (Halliwell and Whiteman, 2004). As the free radical chain takes effect on different cells in the body, different health issues ensue. Cancer results as the chain damages cell membranes and DNA.
Respiratory complications occur due to cell damage in the respiratory tract. Numerous studies have linked oxidative damage to Alzheimer's disease, atherosclerosis, diabetes, and other neurodegenerative diseases (Halliwell and Whiteman, 2004). Free radicals have also been shown to damage lipids, carbohydrates, proteins, and mitochondrial and nuclear DNA.
Damage of these structures also coincides with diseases such as cancer, diabetes, cardiovascular disease, chronic inflammatory disease, and the aging process (Kim et al., 2001).
Furthermore, increased levels of oxygen free radicals lead to increased levels of the hydroxyl free radical. The hydroxyl radical formation in living systems is a proposed product of a transition metal reacting with molecular oxygen (Aust et al., 1999), as shown below.
The hydroxyl radical can attack DNA, causing damage that if not repaired, can lead to mutations.
The negative effects of oxygen free radicals are well known. The production of such free radicals in the body appears to be unavoidable at this time, but the negative effects can theoretically be lessened by means of antioxidants. In theory, as an individual increases the oxygen in his or her body, the level of oxidative stress would increase also.
Different levels of exercise should presumably require different levels of antioxidant supplementation to counter exercise-induced oxidative stress.
Vitamin E, an antioxidant, can be found in numerous foods such as:
- Whole grain breads
- Green leafy vegetables
- Wheat germ
- Vegetable oils
- Dried beans
Vitamin E is a fairly large organic molecule with a molecular weight of 430.7128 g/mol; it is composed of carbon, hydrogen, and oxygen.
These molecules form two hexagonal rings and a carbon chain. Located on the benzene ring is a hydroxyl group. This hydroxyl group is of great importance because it possesses the ability to stabilize free radicals in the body.
Vitamin E reduces oxidative stress via hydroxyl hydrogen, which is able to use it's electron to neutralize the free radical. In turn, vitamin E is left with a free electron.
The newly formed vitamin E free radical will either react with another of the same "species" through a radical-radical reaction, be repaired by Ubiquinone 10 (reduced coenzyme Q), or be recycled with vitamin C (Zheng, 2003).
Vitamin E is a widely known antioxidant, and is the subject of numerous research projects. Consequently, the RDA of vitamin E may, in time, be increased for exercising individuals. Presently, the United States Recommended Daily Allowance of vitamin E is 10mg per day. The hardcore bodybuilder or fitness fanatic should be supplementing with the RDA to reduce and prevent oxidative stress to the body.
- ABC Bodybuilding. [ online ] (accessed December 2004).
- Abu-Qare, A., and Abou-Donia, M., Increased 8-hydroxy-2'-deoxyguanosine, a biomarker of oxidative DNA damage in rat urine following a single dermal dose of DEET (N,N-diethyl-m-toluamide), and permethrin, alone and in combination. Tox. Letters. 2000; 117:151-160.
- Aust, Ann E; Eveleigh, Jamie F. Mechanisms of DNA Oxidation. Soc. for Exp. Biol. and Med. 1999; 222:246-252.
- Chemfinder.com Database. [ online ] (accessed December 2004).
- Halliwell, B., Whiteman, M. Measuring reactive species and oxidative damage in vivo and in cell culture: how should you do it and what do the results mean. Br. J. Pharmacol. 2004; 142:231-255.
- Kim, M-H., Moon, H-R., and Hong, S-H., Determination of urinary 8-hydroxy-2'-deoxyguanosine as a DNA damage marker. Amer. Clin. Lab. 2001; 42-45.
- Oda, Yasushi; Uesugi, Seiichi; Ikehara, Morio; Nishimura, Susumu; Kawase, Yasutoshi; Ishikawa, Hiroyuki; Ohtsuka, Eiko. NMR studies of a DNA containing 8-hydroxydeoxyguanosine. Nucleic Acids Res. 1991; 19: 1407-1412.
- Sigma Aldrich Company. [ online ] (accessed December, 2004).
- Zheng, Xiaomei. Tocopheroxy Radical. Free Radical Biol. Med. 2003; 77:222