
Athletes Need Enough ZincBy Judy
McBride August 17, 1999Peak athletic performance depends on
adequate zinc as well as iron and copper, according to a new study from the
Agricultural Research Service, USDA's chief
scientific agency. While most athletes don't have to worry, those who avoid beef and load up on
carbohydrates may fall short in zinc. Beef is the major source of this
essential trace element in the U.S. diet. Wrestlers, gymnasts and ballerinas
who eat sparingly to maintain a low body weight may also be at risk of not
getting enough zinc. With these athletes in mind, ARSphysiologist Henry C.
Lukaski studied the effects of a low-zinc diet on 12 athletic men in their
twenties. Based at the Grand Forks, N. D., Human Nutrition Research Center,
Lukaski wanted to fill in the limited data on low-zinc intake. He focused on a zinc-containing enzyme--carbonic anhydrase--in red blood
cells. The enzyme helps red blood cells pick up carbon dioxide and drop it off
in the lungs to be exhaled. This exchange helps maintain the chemical
environment muscle cells need to contract and produce energy. If the exchange
is sluggish, the athlete pays the price in performance. For nine weeks each, the men ate a diet containing 18 milligrams of zinc per
day--slightly more than the recommended amount--and another containing only 3
mg/day--one fifth of the recommendation. After the low-zinc diet, the men had significant drops in peak oxygen uptake
and peak carbon dioxide output as they cycled all-out on an ergometer. Their
respiratory exchange ratios also dropped, indicating energy production during
peak exercise was not up to snuff. The low-zinc diet also depressed these measurements while the men cycled at
75 percent of peak capacity. The activity of the carbonic anhydrase enzyme also
was lower after the low-zinc diet. The recommended 12-15 mg/day is adequate for peak performance. Supplementing
with several times that level can cause health risks, researchers caution. Scientific contact: Henry C. Lukaski, ARS
Grand Forks Human Nutrition Research
Center, Grand Forks, N.D., phone (701) 795-8355, fax (701) 795-8395,
[email protected].
U.S. Department of Agriculture | |