Studies of marginal zinc deprivation in rhesus monkeys. VIII. Effects in early adolescence.

Arrested adolescent growth and sexual maturation are striking symptoms of severe dietary zinc deprivation. More general implications of mild or marginal Zn deficiency during adolescence are not known. Five marginally Zn-deprived (ZD) male monkeys (4 mg Zn/kg diet) were compared with five controls pair fed a diet containing 100 mg Zn/kg during early adolescence. Mean plasma Zn levels were 38% lower in ZD group than in controls when evaluations began. During rapid growth plasma Zn decreased in controls but not ZD animals. ZD animals had delayed onset of accelerated weight gain and linear growth; loss of subcutaneous fat typical of early adolescence did not occur. ZD monkeys required two to three times more trials for both learning and reversal a visual discrimination task. Immune function was depressed 20-30% as reflected in early reduced proliferative response of peripheral lymphocytes and later lower immunoglobulin levels. Marginal dietary Zn deprivation affects growth and function in adolescence without producing frank developmental retardation.