OREGON STATE UNIVERSITY

Marathon runners deplete vitamins, raise oxidative stress

02/26/2002

CORVALLIS - A recent study from the Linus Pauling Institute at Oregon State University suggests that intense exercise can actually increase oxidative stress in humans, as the body struggles to detoxify free radicals while muscles use oxygen at 100-200 times their normal rate. In continuing research, scientists hope to identify ways to decrease that oxidative stress. The findings could be of value not only to athletes, but also to people suffering from degenerative diseases that increase oxidative stress, and those who are obese, smoke, or are just couch potatoes in lousy shape.

"Everyone knows that there are many health benefits of exercise, but fewer people understand that it can also cause some metabolic damage," said Maret Traber, an associate professor of nutrition and food management and one of the nation's leading experts on the role of vitamin E in human health.

"When running or doing other intense exercise, there's a 10-20 fold increase in whole body oxygen consumption," Traber said. "This can produce reactive oxygen species, which can be harmful, at rates that exceed the body's natural capacity to detoxify them."

Some theories hold that even the process of muscle strengthening is actually a form of damage control, Traber said. By this perspective, cells and weak muscle fibers may be damaged and replaced by stronger ones. After this type of activity the body is literally in a recovery period.

With a two-year, $100,000 grant from the National Institutes of Health, Traber is studying this process along with Angela Mastaloudis, a doctoral student and holder of a fellowship from the Linus Pauling Institute. The goal, the scientists said, is to better understand the metabolic processes going on when the body faces oxidative stress, its impact on the levels of antioxidants such as vitamins C and E, and ways in which diet or supplements might be used to address this issue for people ranging from top athletes to those who are critically ill.

In this research, they have studied the effects of exercise on ultramarathon runners, people who have competed in races of 50 kilometers, or more than 30 miles, on a route in McDonald Forest near Corvallis, Ore., that also includes a total elevation gain and loss of 12,000 feet. It's not for the faint of heart.

"In our last study of runners who competed in this ultramarathon, we found that this type of intense exercise did increase oxidative stress and deplete levels of vitamin E, and we analyzed 'biomarkers' that also suggest lipid damage," Mastaloudis said.

The findings were published in the professional journal Free Radical Biology and Medicine.

To do their experiments, the researchers literally set up a laboratory complete with expensive analytical instruments in the middle of a conifer forest, doing blood analysis and other measurements just as the runners were completing their exhaustive races.

Another study using the ultramarathoners is planned for this April, and the scientists are now seeking about 20 subjects --- 10 men and 10 women --- to participate. They want to find out if supplementation with vitamins C and E can provide a level of protection against the oxidative stress or metabolic damage caused by exercise. The amount of supplementation to be used --- 1,000 milligrams of vitamin C, 400 international units of natural-form vitamin E --- are far above the recommended daily minimums outlined by federal panels, but are amounts that many people routinely take to supplement their diet. The research will also use a control group that receives placebos.

"This research is not really about enhancing physical performance, that's not the goal and there's little evidence that antioxidant supplements could do that," Traber said. "What's most interesting to us is that some of the markers of lipid damage which we're seeing go up in long-distance runners are the same type of elevated levels we see in people with degenerative diseases, such as diabetes."

The question at hand, Traber and Mastaloudis said, is whether vitamin supplementation can really prevent metabolic damage. It would be impractical and unethical to test this theory in very sick patients, they said, but what is learned from studies of strong athletes make be equally relevant to both groups.

"We need better data on how much vitamin E or other antioxidants you really need in different situations, including athletic stress and chronic disease," Traber said. "Some medical experts say we have not proven that higher levels of antioxidants can prevent disease or have other health benefits. That's largely because we've poured billions of dollars into studying the value of costly prescription medicines, but very little into studying inexpensive supplements such as vitamin E."

The current recommended minimum standards for vitamin E was based mostly on data from the 1950s, Traber said --- she was on the national panel that recently revised those standards. But it's far less clear, she said, what the optimal level of these micronutrients might be for human health and people who have depressed levels for various reasons --- athletic exertion, diseases such as diabetes or heart disease, smoking, obesity, or even lack of physical activity.