Zinc improved the memory of seventh-graders who took part in the research, a study found. A total of 209 of them were involved in a study at the federal Human Nutrition Research Center in Grand Forks from 2002 through 2004.

James Penland, the project's lead researcher, said students who were given 20 milligrams of zinc a day with a glass of orange juice performed better in recalling information than students who were given 10 milligrams or students given a placebo with no zinc.

Penland, a research psychologist, launched the study to help the government determine recommended daily allowances for adolescents, most of which are based on research involving adults.

The study found no ill effects in students' school performance or social interactions from the higher zinc intake, he said. "I'm most confident of the findings with memory," Penland said.

Laurie Tweten, a seventh-grade health teacher at South Middle School in Grand Forks, helped coordinate students' participation in the study. The students were excited to contribute to science, she said, but researchers tabulated the results of the memory and cognitive-learning tasks, so she notice no difference in their classroom performance.

Penland said the risk of zinc deficiency is higher for adolescents because they are going through a time of rapid growth.

"We're in the midst of writing it up for publication," he said of the study, "and I think we're going to try to target adolescents who are more likely to be zinc deficient."