title: Efficacy of iron and/or zinc supplementation on cognitive performance of lead-exposed Mexican schoolchildren: a randomized, placebo-controlled trial.
abstract: OBJECTIVE
  Lead exposure in children has been associated with both global and specific cognitive deficits. Although chelation therapy is advised for children with blood lead concentrations of >44 microg/dL, treatment options for children with lower blood lead values are limited. Because lead absorption is related to children's nutritional status, micronutrient supplements may be 1 strategy for combating low-level, chronic lead exposure. This study was designed to test the efficacy of iron and zinc supplementation for lowering blood lead concentrations and improving cognitive performance in schoolchildren who live in a lead-contaminated city.
  
  
  METHODS
  This randomized, double-blind, placebo-controlled field trial was conducted in public elementary schools in Torreón, an industrialized city in northern Mexico. A metal foundry, located close to the city center and within 3.5 km of 9 schools, was the main source of lead exposure. A total of 602 children who were aged 6 to 8 years and regularly attending first grade in the study schools were enrolled. Children were given 30 mg of iron, 30 mg of zinc, both, or a placebo daily for 6 months. A total of 527 completed the treatment, and 515 were available for long-term follow-up, after another 6 months without supplementation. Eleven cognitive tests of memory, attention, visual-spatial abilities, and learning were administered at baseline and each follow-up.
  
  
  RESULTS
  There were no consistent or lasting differences in cognitive performance among treatment groups.
  
  
  CONCLUSIONS
  Daily supplementation with iron and/or zinc may be of limited usefulness for improving cognition in lead-exposed schoolchildren. However, these treatments may be effective in settings with higher prevalence of nutritional deficiencies or in younger children.
authors.affiliation: Department of Psychology, National Autonomous University of Mexico, Mexico City, Mexico.
authors.forename: Javier Alatorre
authors.initials: JA
authors.lastname: Rico
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Kordas
authors.forename: Patricia
authors.initials: P
authors.lastname: López
authors.forename: Jorge L
authors.initials: JL
authors.lastname: Rosado
authors.forename: Gonzalo García
authors.initials: GG
authors.lastname: Vargas
authors.forename: Dolores
authors.initials: D
authors.lastname: Ronquillo
authors.forename: Rebecca J
authors.initials: RJ
authors.lastname: Stoltzfus
mesh_terms: D002648:Child; D003071:Cognition / Q000187:drug effects*; D004311:Double-Blind Method; D004359:Drug Therapy, Combination; D004522:Educational Status; D004781:Environmental Exposure; D005260:Female; D005293:Ferritins / Q000097:blood; D005296:Ferrous Compounds / Q000008:administration & dosage*; D006801:Humans; D007361:Intelligence Tests; D007854:Lead / Q000097:blood*; D008297:Male; D008669:Metallurgy; D015032:Zinc / Q000097:blood; D015034:Zinc Oxide / Q000008:administration & dosage*
chemical_list: D005296:Ferrous Compounds; D007854:Lead; D005293:Ferritins; D015032:Zinc; C031621:ferrous fumarate; D015034:Zinc Oxide