Effects of iron and zinc supplementation on cognitive function, achievement and behavior of lead-exposed Mexican school children

We conducted a 2 x 2 factorial, placebo-controlled trial of 6-month iron and zinc supplementation among lead-exposed children in Torreón, Mexico (altitude 1060 m). Nine schools were selected based on proximity to a lead smelter and first-graders were individually randomized to daily treatment with 30 mg iron, 30 mg zinc, both, or placebo. In addition to biochemical indicators, cognitive functions were measured: learning (3 assessments), psychomotor speed and visual spatial abilities (5 assessments) and memory and attention (6 assessments).; At baseline, 602 children ages 6.2–8.5 years were enrolled. The mean blood lead concentration (PbB) was 11.5 ± 6.1 μg/dl and 51% of children had concentrations above 10 μg/dl. The prevalence of anemia and stunting was low (10% with hemoglobin < 12.4 g/dl and 2.5% height-for-age z-score < −2 SD). The presence of iron deficiency was moderate (21.4% children with serum ferritin <15 μg/1 and 14.9% with zinc protoporphyrin <80 μmol ZP/mol heme). Lead was negatively associated with 7 of 14 cognitive tests, including 2 tests of learning, 3 tests of psychomotor speed and 2 tests of memory and attention.; Lead levels at baseline were associated with teacher ratings of behavior. The prevalence of problem behavior ratings was higher among children with PbB ≥ 10 μg/dl. Children with higher PbB were also observed in passive behaviors more often than children with leads <10 μg/dl. Lead was not associated with on-task behaviors in class or physical activity at recess.; The supplementation lasted for 147 ± 15 days and the average compliance was 92%. Seventy-five children (13%) were lost to follow-up, yielding a sample of 527 children at short-term follow-up. Iron supplementation improved zinc protoporphyrin by 3.1 μmol/mol heme (p < 0.001). Zinc reduced the benefits of iron on hemoglobin and serum ferritin, whereas iron diminished the effects of zinc on serum zinc.; Cognitive tests showed overall improvement at follow-up (p < 0.01), as expected with age. Iron improved performance on two stimulus discrimination tasks (p < 0.05), but diminished short-term memory outcomes (p = 0.005). Zinc tended to improve visual spatial abilities (p = 0.068). Cognitive effect sizes ranged from 0.12 to 0.19 SD. (Abstract shortened by UMI.)...