The Journal of Nutrition Community and International Nutrition
Zinc Supplementation Sustained Normative Neurodevelopment in a Randomized, Controlled Trial of Peruvian Infants Aged 6–18 Months1,2 John Colombo,3* Nelly Zavaleta,4 Kathleen N. Kannass,5 Fabiola Lazarte,4 Carla Albornoz,4 Leah L. Kapa,6 and Laura E. Caulfield7
Abstract A double-blind, randomized clinical trial was conducted to determine the effects of prevention of zinc deficiency on cognitive and sensorimotor development during infancy. At 6 mo of age, infants were randomly assigned to be administered a daily liquid supplement containing 10 mg/d of zinc (zinc sulfate), 10 mg/d of iron (ferrous sulfate), and 0.5 mg/d of copper (copper oxide), or an identical daily liquid supplement containing only 10 mg/d of iron and 0.5 mg/d of copper. Various controls were implemented to ensure adherence to the supplement protocol. A battery of developmental assessments was administered from 6 to 18 mo of age that included a visual habituation/recognition memory task augmented with heart rate at 6, 9, and 12 mo of age; the Bayley Scales of Infant Development, 2nd edition (BSID2) at 6, 12, and 18 mo; the A-not-B error task at 9 and 12 mo; and free-play attention tasks at 12 and 18 mo. Only infants supplemented with zinc had the normative decline in look duration from 6 to 12 mo during habituation and a normative decline in shifting between objects on free-play multiple-object attention tasks from 12 to 18 mo of age. The 2 groups did not differ on any of the psychophysiologic indices, the BSID2, or the A-not-B error task. The findings are consistent with zinc supplementation supporting a profile of normative information processing and active attentional profiles during the first 2 y of life. This trial was registered at clinicaltrials.gov as NCT00589264. J. Nutr. 144: 1298–1305, 2014.
Introduction Zinc is a trace mineral essential to all forms of life because of its fundamental role in gene expression, cell development, and replication, but millions of people throughout the world have an inadequate concentration of zinc in the diet because of limited access to zinc-rich foods and the abundance of zinc inhibitors common in cereal-based diets (1). Two periods appear to increase the risk of zinc deficiency in the young child: gestation and older infancy. Fetal accumulation of zinc during pregnancy is a function of maternal zinc status, and thus, newborn zinc deficiency (low serum zinc concentration) is likely in populations with inadequate dietary zinc intakes during pregnancy (2). This deficiency is likely transitory for all but the most vulnerable (preterm or low-birth-weight infants) because the zinc content of colostrum is high, and some zinc becomes available to the infant as part of the hematologic changes accompanying the transition to the extra-uterine environment (3). Beginning at around 6 mo of age, however, breast milk intakes no longer provide sufficient 1
This research was supported by grants R01HD045430, P30DC005803, and P30HD02528. 2 Author disclosures: J. Colombo, N. Zavaleta, K. N. Kannass, F. Lazarte, C. Albornoz, L. L. Kapa, and L. E. Caulfield, no conflicts of interest. * To whom correspondence should be addressed. E-mail: [email protected].
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zinc to meet requirements (4), making zinc-rich complementary foods necessary (5). If zinc-rich sources are not available on a routine basis, zinc deficiency develops over time, and concern regarding the potential adverse effects of inadequate zinc intakes on growth and development will continue as long as dietary intakes remain inadequate. Multiple lines of evidence suggest that zinc nutriture influences child development (6,7). Zinc is a critical nutrient for central nervous system development; it is necessary for enzymes involved in brain growth, for proteins that provide brain structure for neurotransmission, and for neurotransmitters involved in brain memory function. Zinc is also involved in steroid hormone transport, receptor binding and metabolism, and neurotransmitter precursor production, all of which ultimately affect brain function (6). In the brain, zinc is found predominantly in the areas that modulate cognitive, behavioral, and affective responses to stimuli, including the hippocampus, the cerebellum (8), and the prefrontal cortex (9). In addition, zinc is concentrated in neurons found in the cortex and the limbic system, particularly in regions providing corticocortico, cortico-limbic, and thalamocortic connections (10,11), where it functions as an important neuromodulator (12). It was postulated that zinc deficiency affects cognitive development during infancy by influencing motor development, activity,
ã 2014 American Society for Nutrition. Manuscript received December 10, 2013. Initial review completed January 7, 2014. Revision accepted May 5, 2014. First published online May 21, 2014; doi:10.3945/jn.113.189365.
Downloaded from jn.nutrition.org at VIRGINIA TECHNICAL UNIVERSITY on August 17, 2014
3 Schiefelbusch Institute for Life Span Studies and Department of Psychology, University of Kansas, Lawrence, KS; 4Nutritional Research Institute, Lima, Peru; 5Department of Psychology, Loyola University of Chicago, Chicago, IL; 6Department of Speech, Language, and Hearing Sciences, University of Arizona, Tucson, AZ; and 7Center for Human Nutrition, Department of International Health, Bloomberg School of Public Health, The Johns Hopkins University, Baltimore, MD
Participants and Methods Study population and recruitment The study was conducted at the Centro de Salud Materno Infantil San Jose in Villa El Salvador, a large shantytown with over 300,000 inhabitants of varying socioeconomic status within the metropolitan area of Lima, Peru. Most homes have electricity and access to safe water and a toilet (although not always within the home). Housing varies from brick (55%) to wood (15%) to cardboard (25%). Micronutrient intake in the diet of children from this population is particularly inadequate for calcium, iron, and zinc (33). The protocol was approved by the institutional review boards at the Instituto de Investigacion ´ Nutricional, the University of Kansas, and The Johns Hopkins University Bloomberg School of Public Health. Potential participants were identified through a field survey of infants 0–6 mo of age and pregnant women. Field workers explained the study to mothers of infants 4–6 mo of age and made an appointment for them at the study clinic. Once there, they learned more about the study and provided signed consent, and we determined their final eligibility for the study. Inclusion criteria were the following: birth weight >2500 g, gestational age >37 wk completed, free from major malformations, 8 Abbreviations used: AT, attention termination; BSID2, Bayley Scales of Infant Development, 2nd edition; FC, supplement containing copper and iron; FCZ, supplement containing iron plus copper and zinc; HR, heart rate; LAZ, length-for-age Z-score; MDI, Mental Development Index; MO, multiple object; PDI, Psychomotor Development Index; SA, sustained attention; SO, single object; WAZ, weight-for-age Z-score.
genetic abnormalities, or health problems associated with developmental delays, no known vision or hearing problems, and no plans to move from the hospital catchment area during the study duration. To avoid potential confounding effects of pre-existing anemia, we took a blood sample via finger prick. Infants with hemoglobin concentrations >103 g/L were considered eligible for enrollment (34); those with concentrations #103 g/L were treated with supplemental iron and followed up separately. Supplementation Random assignment to supplement type was carried out in blocks of 2 within strata based on sex. The FCZ group was administered a liquid supplement containing 10 mg/d of zinc (as zinc sulfate), 10 mg/d of iron (as ferrous sulfate), and 0.5 mg/d of copper (as copper oxide), whereas the FC group was administered an identical liquid supplement containing only 10 mg/d of iron and 0.5 mg/d of copper. The Peruvian Ministry of Health guidelines for preventing iron deficiency anemia in infancy indicate universal supplementation beginning at age 6 mo with 10 mg/d of iron. The dosage of zinc was chosen because it was the most common dose used in prior supplementation studies in this age group. To ensure adequate copper status, given the dosages of iron and zinc, we chose a dosage of copper about twice the 2001 U.S. RDA for 12- to 18-mo-old infants (35). The supplements were prepared by IQFARMA, a certified national laboratory. The supplement bottles and liquids themselves were indistinguishable, and each had a spoon metered to deliver 2.5 mL of supplement. At enrollment, the infants were assigned a unique identification number, which corresponded to the correct supplement type to be taken by the next infant recruited within that stratum. The correspondence between ID number and supplement type was sealed in a document and kept with the manufacturer and the director of the Instituto de Investigacion ´ Nutricional. The investigators, the families of study participants, and data analysts had no knowledge of treatment groups until data analyses were complete. Data collection At enrollment, women were interviewed to gather information on socioeconomic status and family characteristics. All infants were evaluated by a physician and anthropometric measures of weight and length were taken following standard protocols; for analyses, these were expressed as Z-scores (14,36). Mothers were then provided an initial allocation of the supplement and advised to give their infant 1 daily dose. During subsequent monthly pediatric evaluations, the nurse collected the used supplement bottle and provided them with a new one. Each bottle was weighed prior to distribution, and the nurse weighed and then recorded the amount of liquid remaining in each returned bottle. Fieldworkers visited participantsÕ homes weekly to inquire about illnesses since the last visit and supplement administration. Specifically, they asked the mother to recall the days she had given the supplement to her infant since their last visit. Blood samples were taken at 6 (baseline), 12, and 18 mo of age to assess iron, copper, and zinc status. A detailed report on compliance with supplementation and the biochemical findings on infant iron, zinc, and copper status was published (37). Overall median compliance was high (81% of dose delivered) and did not differ over time or by supplement type. At baseline, the mean plasma zinc concentrations in the 2 groups did not vary by supplement type (11.0 6 2.1 and 11.0 6 2.0 mmol/L for the FC and FCZ groups, respectively), with the proportion of children with zinc deficiency (plasma zinc concentrations
Zinc Supplementation Sustained Normative Neurodevelopment in a Randomized, Controlled Trial of Peruvian Infants Aged 6–18 Months1,2 John Colombo,3* Nelly Zavaleta,4 Kathleen N. Kannass,5 Fabiola Lazarte,4 Carla Albornoz,4 Leah L. Kapa,6 and Laura E. Caulfield7
Abstract A double-blind, randomized clinical trial was conducted to determine the effects of prevention of zinc deficiency on cognitive and sensorimotor development during infancy. At 6 mo of age, infants were randomly assigned to be administered a daily liquid supplement containing 10 mg/d of zinc (zinc sulfate), 10 mg/d of iron (ferrous sulfate), and 0.5 mg/d of copper (copper oxide), or an identical daily liquid supplement containing only 10 mg/d of iron and 0.5 mg/d of copper. Various controls were implemented to ensure adherence to the supplement protocol. A battery of developmental assessments was administered from 6 to 18 mo of age that included a visual habituation/recognition memory task augmented with heart rate at 6, 9, and 12 mo of age; the Bayley Scales of Infant Development, 2nd edition (BSID2) at 6, 12, and 18 mo; the A-not-B error task at 9 and 12 mo; and free-play attention tasks at 12 and 18 mo. Only infants supplemented with zinc had the normative decline in look duration from 6 to 12 mo during habituation and a normative decline in shifting between objects on free-play multiple-object attention tasks from 12 to 18 mo of age. The 2 groups did not differ on any of the psychophysiologic indices, the BSID2, or the A-not-B error task. The findings are consistent with zinc supplementation supporting a profile of normative information processing and active attentional profiles during the first 2 y of life. This trial was registered at clinicaltrials.gov as NCT00589264. J. Nutr. 144: 1298–1305, 2014.
Introduction Zinc is a trace mineral essential to all forms of life because of its fundamental role in gene expression, cell development, and replication, but millions of people throughout the world have an inadequate concentration of zinc in the diet because of limited access to zinc-rich foods and the abundance of zinc inhibitors common in cereal-based diets (1). Two periods appear to increase the risk of zinc deficiency in the young child: gestation and older infancy. Fetal accumulation of zinc during pregnancy is a function of maternal zinc status, and thus, newborn zinc deficiency (low serum zinc concentration) is likely in populations with inadequate dietary zinc intakes during pregnancy (2). This deficiency is likely transitory for all but the most vulnerable (preterm or low-birth-weight infants) because the zinc content of colostrum is high, and some zinc becomes available to the infant as part of the hematologic changes accompanying the transition to the extra-uterine environment (3). Beginning at around 6 mo of age, however, breast milk intakes no longer provide sufficient 1
This research was supported by grants R01HD045430, P30DC005803, and P30HD02528. 2 Author disclosures: J. Colombo, N. Zavaleta, K. N. Kannass, F. Lazarte, C. Albornoz, L. L. Kapa, and L. E. Caulfield, no conflicts of interest. * To whom correspondence should be addressed. E-mail: [email protected].
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zinc to meet requirements (4), making zinc-rich complementary foods necessary (5). If zinc-rich sources are not available on a routine basis, zinc deficiency develops over time, and concern regarding the potential adverse effects of inadequate zinc intakes on growth and development will continue as long as dietary intakes remain inadequate. Multiple lines of evidence suggest that zinc nutriture influences child development (6,7). Zinc is a critical nutrient for central nervous system development; it is necessary for enzymes involved in brain growth, for proteins that provide brain structure for neurotransmission, and for neurotransmitters involved in brain memory function. Zinc is also involved in steroid hormone transport, receptor binding and metabolism, and neurotransmitter precursor production, all of which ultimately affect brain function (6). In the brain, zinc is found predominantly in the areas that modulate cognitive, behavioral, and affective responses to stimuli, including the hippocampus, the cerebellum (8), and the prefrontal cortex (9). In addition, zinc is concentrated in neurons found in the cortex and the limbic system, particularly in regions providing corticocortico, cortico-limbic, and thalamocortic connections (10,11), where it functions as an important neuromodulator (12). It was postulated that zinc deficiency affects cognitive development during infancy by influencing motor development, activity,
ã 2014 American Society for Nutrition. Manuscript received December 10, 2013. Initial review completed January 7, 2014. Revision accepted May 5, 2014. First published online May 21, 2014; doi:10.3945/jn.113.189365.
Downloaded from jn.nutrition.org at VIRGINIA TECHNICAL UNIVERSITY on August 17, 2014
3 Schiefelbusch Institute for Life Span Studies and Department of Psychology, University of Kansas, Lawrence, KS; 4Nutritional Research Institute, Lima, Peru; 5Department of Psychology, Loyola University of Chicago, Chicago, IL; 6Department of Speech, Language, and Hearing Sciences, University of Arizona, Tucson, AZ; and 7Center for Human Nutrition, Department of International Health, Bloomberg School of Public Health, The Johns Hopkins University, Baltimore, MD
Participants and Methods Study population and recruitment The study was conducted at the Centro de Salud Materno Infantil San Jose in Villa El Salvador, a large shantytown with over 300,000 inhabitants of varying socioeconomic status within the metropolitan area of Lima, Peru. Most homes have electricity and access to safe water and a toilet (although not always within the home). Housing varies from brick (55%) to wood (15%) to cardboard (25%). Micronutrient intake in the diet of children from this population is particularly inadequate for calcium, iron, and zinc (33). The protocol was approved by the institutional review boards at the Instituto de Investigacion ´ Nutricional, the University of Kansas, and The Johns Hopkins University Bloomberg School of Public Health. Potential participants were identified through a field survey of infants 0–6 mo of age and pregnant women. Field workers explained the study to mothers of infants 4–6 mo of age and made an appointment for them at the study clinic. Once there, they learned more about the study and provided signed consent, and we determined their final eligibility for the study. Inclusion criteria were the following: birth weight >2500 g, gestational age >37 wk completed, free from major malformations, 8 Abbreviations used: AT, attention termination; BSID2, Bayley Scales of Infant Development, 2nd edition; FC, supplement containing copper and iron; FCZ, supplement containing iron plus copper and zinc; HR, heart rate; LAZ, length-for-age Z-score; MDI, Mental Development Index; MO, multiple object; PDI, Psychomotor Development Index; SA, sustained attention; SO, single object; WAZ, weight-for-age Z-score.
genetic abnormalities, or health problems associated with developmental delays, no known vision or hearing problems, and no plans to move from the hospital catchment area during the study duration. To avoid potential confounding effects of pre-existing anemia, we took a blood sample via finger prick. Infants with hemoglobin concentrations >103 g/L were considered eligible for enrollment (34); those with concentrations #103 g/L were treated with supplemental iron and followed up separately. Supplementation Random assignment to supplement type was carried out in blocks of 2 within strata based on sex. The FCZ group was administered a liquid supplement containing 10 mg/d of zinc (as zinc sulfate), 10 mg/d of iron (as ferrous sulfate), and 0.5 mg/d of copper (as copper oxide), whereas the FC group was administered an identical liquid supplement containing only 10 mg/d of iron and 0.5 mg/d of copper. The Peruvian Ministry of Health guidelines for preventing iron deficiency anemia in infancy indicate universal supplementation beginning at age 6 mo with 10 mg/d of iron. The dosage of zinc was chosen because it was the most common dose used in prior supplementation studies in this age group. To ensure adequate copper status, given the dosages of iron and zinc, we chose a dosage of copper about twice the 2001 U.S. RDA for 12- to 18-mo-old infants (35). The supplements were prepared by IQFARMA, a certified national laboratory. The supplement bottles and liquids themselves were indistinguishable, and each had a spoon metered to deliver 2.5 mL of supplement. At enrollment, the infants were assigned a unique identification number, which corresponded to the correct supplement type to be taken by the next infant recruited within that stratum. The correspondence between ID number and supplement type was sealed in a document and kept with the manufacturer and the director of the Instituto de Investigacion ´ Nutricional. The investigators, the families of study participants, and data analysts had no knowledge of treatment groups until data analyses were complete. Data collection At enrollment, women were interviewed to gather information on socioeconomic status and family characteristics. All infants were evaluated by a physician and anthropometric measures of weight and length were taken following standard protocols; for analyses, these were expressed as Z-scores (14,36). Mothers were then provided an initial allocation of the supplement and advised to give their infant 1 daily dose. During subsequent monthly pediatric evaluations, the nurse collected the used supplement bottle and provided them with a new one. Each bottle was weighed prior to distribution, and the nurse weighed and then recorded the amount of liquid remaining in each returned bottle. Fieldworkers visited participantsÕ homes weekly to inquire about illnesses since the last visit and supplement administration. Specifically, they asked the mother to recall the days she had given the supplement to her infant since their last visit. Blood samples were taken at 6 (baseline), 12, and 18 mo of age to assess iron, copper, and zinc status. A detailed report on compliance with supplementation and the biochemical findings on infant iron, zinc, and copper status was published (37). Overall median compliance was high (81% of dose delivered) and did not differ over time or by supplement type. At baseline, the mean plasma zinc concentrations in the 2 groups did not vary by supplement type (11.0 6 2.1 and 11.0 6 2.0 mmol/L for the FC and FCZ groups, respectively), with the proportion of children with zinc deficiency (plasma zinc concentrations
