Exercise: A Radical Proposition

By Judith Norkin

The annual meeting of the American Aging Association examined how exercise, as good as it may be for us, carries a downside in the excessive production of free radicals. Here's what that might mean for middle-aged and older adults.

The most recent meeting of the American Aging Association (AGE), held in Philadelphia, gave an enthusiastic "thumbs-up" on behalf of exercise, but with more than a nod toward its dangers as well. The conference hosted scientists from around the world presenting material on such topics as the mechanical and biochemical effects of exercise, the cognitive changes caused by aging, new diagnostic tools being used to evaluate physical fitness, and studies showing how exercise improves the health of older men and women.

But one of the most interesting aspects of exercise dealt with free radicals, how exercise-ostensibly good for us- may produce these harmful agents in our bodies, and what we can do about it. While exercise may be beneficial, scientists said, dealing with the free radicals that are an ultimate result of exercise can be a crucial consideration.

Free radicals are highly reactive molecules produced in the body, often derived from oxygen, that carry an unpaired electron on their surface, making them prone to causing damage to other molecules they encounter. The ongoing, damaging effects of free radicals may be involved in aging and degenerative disease.

According to Donald Ingram, Ph.D., current AGE president and a research psychologist at the Gerontology Research Center of the National Institute on Aging, in Baltimore (and also a member of the Life Extension Foundation's Scientific Advisory Board), "In examining the cellular and molecular mechanisms of aging in humans and animals, it is clear that the benefits of exercise represent a delicate balance between anabolic and catabolic forces involving oxygen radicals. Acute exercise increases metabolism and thus increases generation of potentially damaging oxygen radicals."

Of particular interest is the role of antioxidants in fighting the damage done by free radicals. Antioxidants react with and neutralize oxygen free radicals generated during normal metabolism. Natural antioxidants that can be taken as supplements to fight free radicals include vitamin C, vitamin E and beta carotene. as well as internally produced enzymes such as peroxide dismutase (SOD), catalase and glutathione peroxidase.

Charlotte Tate, Ph.D., professor of pharmacology at the University of Houston, and president of the American College of Sports Medicine, also touched on the paradoxical nature of this issue. "It's what we call the oxygen paradox," said Tate. "We need oxygen to live, but it produces free radicals. What the body has done to combat the paradox is to design enzymes and systems to scavenge free radicals. The key here appears to be that, when you age, you lose that ability, and the free radicals start doing bad things."

In Tate's view, the body's natural scavenging ability may adequately protect it from free radical damage, but with age, the body may have difficulty defending itself and thus be more prone to free radical damage.

Figuring out how to combat the effects of free radical damage in the aging body was a research goal for Arthur C. Cosmas, Ph.D., of the University of Connecticut. Cosmas suggested that free radical damage could be curtailed by limiting exercise after the early 40s, when people hit what he calls the "threshold age," when vulnerability to free radical damage increases.

"Exercise affects young people differently than older ones," said Cosmas. "We know physical activity causes the generation of free radicals. Younger animals have the antioxidant enzymes to neutralize free radicals before they cause damage. But as an organism ages, its ability to produce enzymes seems to diminish and it's less able to mend. We've found that exercise of a particular intensity might be fine for the body at a young age, but an older body may not be able to adapt to that level, and there are some potentially deleterious effects."

According to Cosmas, reducing the intensity of activity after the threshold age is beneficial because, at lower intensity, fewer free radicals will be produced and the body may be able to deal with them in lower concentration.

If free radical by-products of exercise do in fact pose a risk, should supplemental antioxidants be used regularly? Opinions at the conference varied. Mitchell Kanter, Ph.D., principal scientist with Quaker Oats, says free radical production may be "the dark side of exercise," but adds that too little is known to draw definitive conclusions.

"Experimental protocols in this field have varied, making it difficult to come down on either side of the antioxidant issue," he said. "Research conducted with 'mainstream' nutrients such as vitamins C and E have produced contradictory findings, although studies done with elderly subjects have been promising."

In general, Kanter suggests that the benefit of antioxidants may be greatest for those middle-aged and older whose bodies have diminishing amounts of antioxidants naturally produced in the body.

Thomas Manfredi, Ph.D., a researcher at the University of Rhode Island, warned against using antioxidants from unknown sources. "With mainstream vitamins such as C and B you can pretty much be assured that you are getting what the bottle says. But some things aren't so tightly regulated, and you have to be careful that anything you buy is taken in prudent doses and produced by reputable companies, especially the more exotic sounding herbs you hear about."

The Life Extension Foundation has long held that supplements should be taken in the proper doses shown by scientific studies to have actually produced benefits. In addition, supplements must be of high quality, meaning they are produced to the same exactingly high standards as the compounds used by scientists in research labs. It is those studies and their results, after all, that form the basis for the Foundation's support of nutritional supplements.

While researchers agreed that exercise increases free radical production, there was not a consensus about its health risk.

"I think there's a consensus of opinion that free radical generation increases with exercise," noted Manfredi. "But what are the biological implications of that? Based on what we've heard, intuitively we say that's not a good thing, but nobody has proven that."

"The antioxidant thing is really interesting but the conundrum is that although exercise produces lots of free radicals and people who exercise show evidence of genetic damage, there's no evidence that this interferes with function," said Kevin McCully, Ph.D., of the department of medicine at Allegheny University of Health Sciences. "Perhaps the muscles are designed to handle the damage. There's still a lot we need to learn here."

The Life Extension Foundation has pointed out that research is constantly clarifying how free radicals produced by exercise can be neutralized by antioxidants. Free radicals generated during exercise are most prevalent in the mitochondria, the energy producing factories in our cells. The best way of countering these free radicals, the Foundation advises, is to replenish the antioxidants that combat them naturally. Those antioxidants include alpha lipoic acid and coenzyme Q10.

Since antioxidants have not been shown to have any negative effects-and may, indeed, have a great deal of benefits in neutralizing free radicals and warding off the ravages of age-some researchers at the conference recommend using them as an "insurance policy."

"When people age they tend to not eat well-not enough calories and an unbalanced diet," said McCully. "Nutritional supplements can help them. There is still so much unknown about antioxidant supplements, but they don't appear to be harmful. What we may find is that it's not a general level of free radicals that are important, it's how they affect specific parts of the body. In other words, specific organs may be more vulnerable to free radical damage than others."

For more information about the American Aging Association, write to AGE, 2129 Providence Ave., Chester, Penn. 19013. Or call 1-215-874-7550.

Although it is well known that excessive weight gain is related to the diseases of aging, Barbara Hansen, Ph.D., from the University of Maryland Medical School, in Baltimore, notes that, "Exercise is not really an effective means of reducing body fat. The propensity for obesity is in the genes. Body fat can be altered by a small degree, say 10 percent, but fewer than 5 percent of the population can move their body weight by more than 10 percent and keep it off."

Hansen detailed how rhesus monkeys exhibit the same genetic differences in the relationship between diet and weight. When different individual animals are fed the same balanced diet, some monkeys will be thin and others will put on a great deal of added weight; it's the same with people.

Hansen admits there is some evidence that exercise does help people keep weight off. But she says that activity is good for other reasons. She advocated exercise for its ability to strengthen muscles, heart and lungs, improve flexibility and to confer psychological benefits.