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Antioxidant Potential Probed
By Marcia Wood
October 29, 2002
Zinc, a mineral essential to human
health, may help protect cells against oxidative damage. A preliminary study by
Agricultural Research Service scientists
has pinpointed the mineral's little-known role as an antioxidant. Janet C. King
and Leslie R. Woodhouse at the ARS Western
Human Nutrition Research Center, Davis, Calif., and Barbara Sutherland, now
with the University of California, Davis,
conducted the study, along with colleagues from the
University of California, Berkeley.
Zinc may safeguard red blood cell membranes against oxidative effects of
other minerals such as copper or iron. Cell membranes keep cell contents in
place and selectively allow salts and other compounds to flow in and out.
The findings suggest that cell membrane health may be an early, accurate
indicator of an individual's zinc needs. In addition, the findings emphasize
the importance of consistently consuming enough zinc from such foods as beans,
whole grains, shellfish, red meat or dark-meat poultry.
The researchers worked with eight healthy men, aged 27 to 47, who
volunteered for the 20-week experiment. The foods that the volunteers ate
provided only 4.6 milligrams of zinc, the amount recommended by the
United Nations' World Health Organization. For the first five
and last five weeks of the study, they also took gelatin capsules that
provided, by day's end, an additional 9.1 milligrams of zinc. For the middle 10
weeks of the experiment, the capsules were replaced with placebos, meaning the
only zinc provided during that time was the 4.6 milligrams from the food.
Volunteers' red blood cell membranes were significantly more fragile when
measured after the 10-week, low-zinc stint. This cell membrane change occurred
in the absence of standard indicators of zinc deficiency, according to the
researchers. They used several different laboratory procedures, including one
known as an osmotic fragility test, to assess membrane strength. Woodhouse
summarized the research at a recent conference of the International Society for
Trace Element Research in Humans, held in Quebec City, Canada.
ARS is the U.S. Department of
Agriculture's chief scientific research agency.