Effects of Iron and/or Zinc Supplementation in Mexican School Children Exposed to Lead

Effects of Iron and Zinc Supplementation on Neuropsychological and Educational Achievement in Lead-exposed School Children

National Institute of Medical Sciences and Nutrition, Salvador Zubiran, National Polytechnic Institute, Mexico

Lead is negatively linked to nutritional status, behavior and cognition in children. Despite extensive knowledge of its toxicity and efforts to reduce exposure, lead continues to be a problem in developed and developing countries. When lead exposure is unavoidable due to its pervasive nature, effective means of protecting or disrupting that exposure need to be developed. Nutritional interventions are one such option. We conducted a 2x2 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 and behavior were evaluated at baseline, after the 6-month supplementation period, and again after another 6 months (without supplementation). At baseline, 602 children ages 6.2-8.5 years were enrolled.

We conducted a 2x2 factorial, placebo-controlled trial of 6-month iron and zinc supplementation among lead-exposed children in Torreón, Mexico (altitude 1060 m) to test the hypothesis that supplementation with iron, zinc or both will reduce blood lead concentrations of the children and improve their cognition and behavior. 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 (blood lead, serum ferritin, CRP, serum zinc, urinary arsenic concentrations), cognitive functions and behavior were measured. Assessments were conducted at three time points: at baseline, after the 6 month treatment, and again after another 6 months without treatment. At baseline, 602 children ages 6.2-8.5 years were enrolled.

Tablet, formulated as ferrous fumarate 30 mg plus zinc oxide 30 mg. Given once daily by mouth for 6 months.

Sugar tablet formulated to look like the experimental arms of the study. Given daily by mouth for 6 months.

Inclusion Criteria: 1st grade child Exclusion Criteria: Blood lead concentration =>45 ug/dL Hemoglobin concentration < 9 g/dL

Kordas K, Lopez P, Rosado JL, Garcia Vargas G, Alatorre Rico J, Ronquillo D, Cebrian ME, Stoltzfus RJ. Blood lead, anemia, and short stature are independently associated with cognitive performance in Mexican school children. J Nutr. 2004 Feb;134(2):363-71. doi: 10.1093/jn/134.2.363.

Kordas K, Canfield RL, Lopez P, Rosado JL, Vargas GG, Cebrian ME, Rico JA, Ronquillo D, Stoltzfus RJ. Deficits in cognitive function and achievement in Mexican first-graders with low blood lead concentrations. Environ Res. 2006 Mar;100(3):371-86. doi: 10.1016/j.envres.2005.07.007. Epub 2005 Sep 19.

Kordas K, Stoltzfus RJ, Lopez P, Rico JA, Rosado JL. Iron and zinc supplementation does not improve parent or teacher ratings of behavior in first grade Mexican children exposed to lead. J Pediatr. 2005 Nov;147(5):632-9. doi: 10.1016/j.jpeds.2005.06.037.

Rico JA, Kordas K, Lopez P, Rosado JL, Vargas GG, Ronquillo D, Stoltzfus RJ. Efficacy of iron and/or zinc supplementation on cognitive performance of lead-exposed Mexican schoolchildren: a randomized, placebo-controlled trial. Pediatrics. 2006 Mar;117(3):e518-27. doi: 10.1542/peds.2005-1172.

Rosado JL, Lopez P, Kordas K, Garcia-Vargas G, Ronquillo D, Alatorre J, Stoltzfus RJ. Iron and/or zinc supplementation did not reduce blood lead concentrations in children in a randomized, placebo-controlled trial. J Nutr. 2006 Sep;136(9):2378-83. doi: 10.1093/jn/136.9.2378.

Rosado JL, Ronquillo D, Kordas K, Rojas O, Alatorre J, Lopez P, Garcia-Vargas G, Del Carmen Caamano M, Cebrian ME, Stoltzfus RJ. Arsenic exposure and cognitive performance in Mexican schoolchildren. Environ Health Perspect. 2007 Sep;115(9):1371-5. doi: 10.1289/ehp.9961.

Kordas K, Casavantes KM, Mendoza C, Lopez P, Ronquillo D, Rosado JL, Vargas GG, Stoltzfus RJ. The association between lead and micronutrient status, and children's sleep, classroom behavior, and activity. Arch Environ Occup Health. 2007 Summer;62(2):105-12. doi: 10.3200/AEOH.62.2.105-112.

Roy A, Kordas K, Lopez P, Rosado JL, Cebrian ME, Vargas GG, Ronquillo D, Stoltzfus RJ. Association between arsenic exposure and behavior among first-graders from Torreon, Mexico. Environ Res. 2011 Jul;111(5):670-6. doi: 10.1016/j.envres.2011.03.003. Epub 2011 Mar 25.

Moodie S, Ialongo N, Lopez P, Rosado J, Garcia-Vargas G, Ronquillo D, Kordas K. The conjoint influence of home enriched environment and lead exposure on children's cognition and behaviour in a Mexican lead smelter community. Neurotoxicology. 2013 Jan;34:33-41. doi: 10.1016/j.neuro.2012.10.004. Epub 2012 Oct 27.

Kordas K, Roy A, Lopez P, Garcia-Vargas G, Cebrian ME, Vera-Aguilar E, Rosado JL. Iron and Zinc Supplementation Does Not Impact Urinary Arsenic Excretion in Mexican School Children. J Pediatr. 2017 Jun;185:205-210.e1. doi: 10.1016/j.jpeds.2017.02.040. Epub 2017 Mar 23.