April 4, 2005 -- Middle school students might do a bit better in class if they consume enough zinc, new research suggests.
That's based on a relatively small and brief study of nearly 200 seventh-grade students. Their mental performance and in-school behavior were noted before and after taking zinc or a placebo for 10 weeks.
The results show better mental performance in the students who took zinc. But overdoing it might not be a great idea. Only a small amount of zinc was tested, not megadoses. It's possible to get too much zinc, says the National Institutes of Health (NIH).
Zeroing in on Zinc
Zinc is an essential mineral. The body uses it in lots of different ways. Those include healing wounds, maintaining a healthy immune system, and growth and development during pregnancy, childhood, and adolescence, says the NIH. It also plays an important role in neurological and reproduction functions.
Zinc has also been linked to thinking, behavior, and motor skills in very young children and adults, the new study notes. Is that also true for teens? No one knew for sure, say the researchers, who work in North Dakota at the U.S. Department of Agriculture's Grand Forks Human Nutrition Research Center.
"There have been no studies of older children who may be at risk of zinc deficiency while undergoing rapid growth during puberty," write James Penland and colleagues. They set out to change that with a 10-week experiment.
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.
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
- 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.