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Marathon Runners
Deplete Vitamins, Raise Oxidative Stress.
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 ultra-marathon 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 ultra-marathon, 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
ultra-marathoners 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.
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