By Kathleen Doheny
April 4, 2005
Study found 20 milligrams a day improved memory, attention span in seventh graders.
Zinc may give your teenager a mental edge. Researchers found that adding the mineral to the diets of middle schoolers led to improvements in their memories and attention spans. They reported the results on April 4 at the Experimental Biology 2005 meeting in San Diego.
Seventh graders given 20 milligrams of zinc five days a week for 10 to 12 weeks performed better on memory tasks and had longer attention spans than did those who did not receive zinc supplements, said James G. Penland, a research psychologist at the U.S. Department of Agriculture's Grand Forks Human Nutrition Research Center, in North Dakota.
Zinc has been studied in relation to motor function, thinking and social skills in very young children and in adults, Penland said, but "this is the first study to look at that relationship in adolescence." These older children may be at risk for zinc deficiency, especially while undergoing rapid growth during puberty, he added.
The current daily requirement for zinc is 11 milligrams for boys aged 14 to 18; 9 milligrams for girls aged 14 to 18, and 8 milligrams for kids aged 9 to 13, Penland said.
His team studied 209 seventh grade boys and girls who consumed 4 ounces of fruit juice that came one of three ways: with no zinc, 10 milligrams of the supplement, or 20 milligrams of the mineral every weekday for 10 weeks. The kids didn't know if they got the juice with zinc or without.
They were then given a battery of tests to measure attention, perception, memory and reasoning. Those given 20 milligrams of zinc answered questions on a visual memory task test 12 percent more accurately and quickly, compared to 6 percent for those not given extra zinc. The group given 20 milligrams of zinc increased the number of questions answered correctly on a word recognition task by 9 percent, compared to 3 percent for the no-zinc group. The group that got just 10 milligrams a day of zinc did not show improved performance.
Some of the tasks involved tapping a key on a keyboard as quickly as possible, using a mouse to follow an object moving across the computer screen, learning, and remembering lists of word and categorizing objects.
Exactly how zinc improved performance isn't known, Penland said. "Deficiencies of zinc alter the function of the hippocampus, which is associated with memory functioning," he noted.
Zinc also helps regulate cell growth, helps wounds heal, and boosts the immune system.
Another expert calls the study "out-of-the-box" thinking. "This is news to me," said Dr. Ken Fujioka, director of nutrition and metabolic research at Scripps Clinic in La Jolla, Calif. "I have not seen this type of study done particularly in this age group."
But he cautions parents not to supplement their children with zinc without checking first with the pediatrician or family doctor. "If you take too much zinc for too long, you can also run into problems," he said.
Added Penland: "My advice to parents would be to look at their kids' diet and make sure it provides the recommended amount of zinc and other nutrients."
Good sources of zinc include meat, seafood, eggs and milk, according to the American Dietetic Association.
Penland hopes more research will be done focusing on older children's dietary needs "because the dietary guidelines that are out there are simply not based on data collected directly from children, by and large. The recommendations [for children] are based on the best data available, but not the best data possible."