A study led by Dr. James Penland of the Agricultural Research Service of the Department of Agriculture randomly assigned 209 seventh graders to one of three groups. The first group received 4oz. of juice containing 20mg of zinc daily, the second drank the same juice with 10mg, and the third drank the juice alone with no zinc.
At the beginning and end of the 12-week study, students were tested for attention, memory, problem-solving and hand-eye coordination.
Those who had taken 20mg of zinc increased their scores significantly on visual memory, word recognition, and attention and vigilance tasks compared with the plain-juice drinkers.
If further studies confirmed those results, Penland contends, it might follow that the current recommended dietary allowance for zinc of 10mg should be increased for adolescents.
“The prudent thing to do would not be to run out and buy zinc supplements, but to make sure that teenagers get the recommended 9mg to 11mg of zinc per day.” He suggests lean red meat, fish and some grains as good sources of zinc.