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

Despite the widespread incidence of childhood zinc (Zn) deficiency and stro ng evidence that Zn deprivation during periods of rapid growth affect brain development and behavior in animals, there is little research on the behav ioral effects of Zn deficiency in children or adults. A brief review of pre vious human studies is followed by more detailed discussion of recent studi es of Chinese and Mexican-American children, which showed beneficial effect s of Zn repletion on neuropsychologic function. Methodology issues are revi ewed 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 m ore accurately; 3) continuous activity and rest in older children by the us e of electronic activity monitors; and 4) electrophysiologic measures of br ain function. It is concluded that research on cognition, behavioral activi ty and brain electrophysiology as outcomes of Zn deficiency and response to improved Zn nutrition is critical, given that Zn deficiency is common in b oth developing and developed countries.