By Jack Challem
Copyright © 1997 by Jack Challem, The Nutrition Reporter™
All rights reserved.
Most people know that physical activity is good for health. However, in one of the ironies of biology, regular and strenuous exercise can increase formation of dangerous free radicals. These rogue molecules damage cell membranes, proteins, and deoxyribonucleic acid (DNA) - the material that forms your genes. The long-terms consequences may be faster aging and an increased risk of cancer.
The solution, according to a top antioxidant researcher, is not to become an exercise-avoiding couch potato. It's to make sure you take your antioxidants, including vitamins E and C and coenzyme Q10.
Lester Packer, PhD, of the University of California, Berkeley, has conducted extensive research on how exercise stimulates production of free radicals and how antioxidants minimize their damage. He reviewed his findings and those of other researchers in a recent article in the Journal of Sports Sciences.
Normally, "there is a delicate balance between oxidants [free radicals] and antioxidants in biological systems," Packer wrote. Both are essential for converting food into energy. Yet exercise, like disease, can tip the balance toward excessive free radical production.
Most free radicals - molecules missing an electron - are produced when cells burn glucose and fats for energy. This energy is carried by electrons, which are largely contained within chemical reactions and by antioxidants, such as vitamins E and C. However, during exercise, oxygen consumption can increase 10-20 times, with electrons leaking beyond the energy-producing chemical reactions. When they do, they can overwhelm the body's antioxidant defenses and lead to large numbers of free radicals injuring nearby cells.
Other free radicals are produced during a process known as ischemia-reperfusion. Ischemia describes the narrowing of blood vessels, which redirects oxygen-rich blood away from many organs and tissues and to muscles. When a person stops exercising, normal blood flow resumes and tissues become reoxygenated. This reoxygenation of oxygen-deprived tissues generates still more free radicals.
Animal and human studies have found that exercise-induced free radicals dramatically increase the oxidation of cell proteins. In particular, the oxidation of DNA can have serious long-term effects, and might speed the aging process and increase the risk of cancer.
However, a number of researchers, including Packer, have found that vitamin E supplements can prevent exercise-induced free radical damage to cells, including the breakage of DNA strands.
While Packer doubts that antioxidant supplements can increase exercise performance, they do appear to reduce exercise-induced fatigue. In one animal study, a diet deficient in vitamin E reduced endurance. Restoring vitamin E might correct the situation, giving the appearance of increased endurance.
"There is some evidence that bolstering cellular antioxidant status may increase muscle resistance to fatigue," Packer wrote. In one study, pretreatment with N-acetylcysteine, an antioxidant that boosts levels of glutathione, a major cellular antioxidant, increased physical output in animals by 15 percent.
In a separate study of exercisers, researchers found that a combination of antioxidants slowed the oxidation of low-density lipoprotein (LDL) cholesterol, considered a risk factor for coronary heart disease.
Tommi J. Vasankari, PhD, of the University of Turku, Finland, gave a small group of endurance athletes either a placebo or an antioxidant supplement containing 294 mg of vitamin E, 1,000 mg of vitamin C, and 60 mg of coenzyme CoQ10 daily daily for four weeks.
The supplements increased LDL's antioxidant capacity by 30-40 percent, both before and after exercise.
References: Packer L, "Oxidants, antioxidant nutrients and the athlete," J Sports Sciences, 1997;15:353-63; Vasankari TJ, Kujala UM, Vasankari TM, et al., "Increased serum and low-density-lipoprotein antioxidant potential after antioxidant supplementation in endurance athletes," Am J Clin Nutr, 1997;65:1052-6.
This article originally appeared in The Nutrition Reporter™ newsletter. The information provided by Jack Challem and The Nutrition Reporter™ newsletter is strictly educational and not intended as medical advice. For diagnosis and treatment, consult your physician.