Zinc May Help Middle School Students Thinking

First, the students -- 111 girls and 98 boys -- took tests covering mental skills like memory, attention, perception, and reasoning. Their teachers also gauged the students' behavior in class.

Next, the students drank fruit juice containing 0, 10, or 20 milligrams of zinc each school day for 10 weeks. After 10 weeks, they retook the tests and the teachers reviewed student conduct again. The U.S. recommended dietary allowance for zinc in adolescents ranges from 9-11 milligrams per day.

The seventh-graders who took 20 milligrams of zinc fared best. Their reaction times on a visual memory test became 12% quicker, their scores on a word recognition test improved by 9%, and their results on a task requiring sustained attention rose by 6%.

The placebo group also improved, but their gains were smaller. Their reaction times fell 6% on the visual memory test, their word recognition test scores increased by 3%, and their results on the attention-based test inched up by 1%.

Behavior Held Steady

When it came to in-class conduct, the zinc takers didn't change. They didn't act up more or behave better than usual.

However, conduct problems increased by 10% in the girls taking the placebo. The reasons for that aren't clear.

"Young adolescents may benefit from increased zinc intakes and underscore the need to further determine the functional roles of zinc nutrition in older children," the researchers write.

The findings were presented at Experimental Biology 2005, a conference being held in San Diego.

Zinc Sources

Oysters are the No. 1 food source for zinc, says the Clinical Nutrition Service of the NIH. Other sources include:

• Fortified breakfast cereals (check the nutrition label)
• Red meat
• Poultry
• Pork
• Beans
• Nuts
• Whole grains
• Dairy products
• Some seafood

Zinc supplements are also available. Taking zinc supplements with certain antibiotics decreases absorption of the antibiotic and reduces its efficacy. Taking zinc supplements and antibiotics at least two hours apart should prevent this from occurring.

SOURCES: Experimental Biology 2005, San Diego, April 2-6, 2005. News release, Federation of American Societies for Experimental Biology. Clinical Nutrition Service, Office of Dietary Supplements, National Institutes of Health, "Facts About Dietary Supplements: Zinc." Linus Pauling Institute.