Vitamin E may counteract effect of free radicals
(Miami University)
Citation: Cancer Weekly, March 22, 1993 p8(2)
Subjects: Vitamin E Physiological aspects
Free radicals (Chemistry) Physiological aspects
Exercise Physiological aspects
Full Text COPYRIGHT Charles Henderson, Publisher 1993
Miami University
Researchers concede they can't prove its value, but some believe
additional vitamin E is a good idea for exercisers worried about
potentially dangerous free radicals, which have been implicated in cell
damage ranging from cancer and heart disease to aging.
The researchers are looking at signs that exercise increases production
of free radicals.
The radicals are unstable oxygen molecules with an extra electron that
try to become balanced by latching onto more electrons, setting off a
chain of electron -grabbing that batters other molecules. "Right now, as
you are breathing air, about 5 percent of the oxygen is breaking down
into free radicals," said Helaine M. Alessio, associate professor of
exercise physiology at Miami University in Oxford, Ohio. When you
exercise, your oxygen consumption easily could increase tenfold, so your
production of free radicals could theoretically increase tenfold as
well, Alessio said. But researchers don't yet know exactly how much free
radicals do increase or what the consequences are, she said.
And one prominent researcher doubts the effects are meaningful in
practice. "This is an interesting idea here, and there's no question
from these observations that in the short run exercise may yield higher
indices of oxidative stress," said Dr. Charles H. Hennekens, professor
of medicine and preventive medicine at Harvard Medical School,
Cambridge, Massachusetts. But Hennekens says these effects seem to be
short -term and overbalanced by the obvious good that exercise does. He
notes that exercise is associated with reduced risk of heart disease and
some forms of cancer - which works against the argument that free
radicals raise an exerciser's risk of those conditions.
To an extent, free radicals are good because they work as part of the
white blood cell's defenses against infection and injury, said Lester
Packer, professor of molecular and cell biology at the University of
California, Berkeley. But they can get out of hand, he said. Free
radicals can damage cell membranes and protein, said Robert R. Jenkins,
a professor of biology at Ithaca College in Ithaca, New York. "The major
concern would be cell damage where free radicals actually enter the
nucleus and affect DNA," said Alessio. "Once you do that, you're talking
the next generation of cells."
Several antioxidant enzymes work to control oxygen free radicals,
according to researcher Li Li Ji of the University of Illinois, Urbana.
And it appears that the stress of exercise makes skeletal muscle more
efficient in using these enzymes, Ji wrote in Medicine and Science in
Sports and Exercise, the journal of the American College of Sports
Medicine. The journal published a five-part section on free radicals.
Vitamins C and E and the compound beta-carotene also act as
antioxidants, but whether exercisers need supplements is unproven,
Alessio said. |
