Behavioral data and methodology issues in studies of zinc nutrition in humans.

Despite the widespread incidence of childhood zinc (Zn) deficiency and strong evidence that Zn deprivation during periods of rapid growth affect brain development and behavior in animals, there is little research on the behavioral effects of Zn deficiency in children or adults. A brief review of previous human studies is followed by more detailed discussion of recent studies of Chinese and Mexican-American children, which showed beneficial effects of Zn repletion on neuropsychologic function. Methodology issues are reviewed and recommendations are made to assess the following: 1) a broad range of cognitive, psychomotor, emotional and social factors; 2) performance in the presence of secondary stressors to approximate real-world conditions more accurately; 3) continuous activity and rest in older children by the use of electronic activity monitors; and 4) electrophysiologic measures of brain function. It is concluded that research on cognition, behavioral activity and brain electrophysiology as outcomes of Zn deficiency and response to improved Zn nutrition is critical, given that Zn deficiency is common in both developing and developed countries.