Zinc intake, status and indices of cognitive function in adults and children: a systematic review and meta-analysis.
In developing countries, deficiencies of micronutrients are thought to have a major impact on child development; however, a consensus on the specific relationship between dietary zinc intake and cognitive function remains elusive. The aim of this systematic review was to examine the relationship between zinc intake, status and indices of cognitive function in children and adults. A systematic literature search was conducted using EMBASE, MEDLINE and Cochrane Library databases from inception to March 2014. Included studies were those that supplied zinc as supplements or measured dietary zinc intake. A meta-analysis of the extracted data was performed where sufficient data were available. Of all of the potentially relevant papers, 18 studies met the inclusion criteria, 12 of which were randomised controlled trials (RCTs; 11 in children and 1 in adults) and 6 were observational studies (2 in children and 4 in adults). Nine of the 18 studies reported a positive association between zinc intake or status with one or more measure of cognitive function. Meta-analysis of data from the adult's studies was not possible because of limited number of studies. A meta-analysis of data from the six RCTs conducted in children revealed that there was no significant overall effect of zinc intake on any indices of cognitive function: intelligence, standard mean difference of <0.001 (95% confidence interval (CI) -0.12, 0.13) P=0.95; executive function, standard mean difference of 0.08 (95% CI, -0.06, 022) P=0.26; and motor skills standard mean difference of 0.11 (95% CI -0.17, 0.39) P=0.43. Heterogeneity in the study designs was a major limitation, hence only a small number (n=6) of studies could be included in the meta-analyses. Meta-analysis failed to show a significant effect of zinc supplementation on cognitive functioning in children though, taken as a whole, there were some small indicators of improvement on aspects of executive function and motor development following supplementation but high-quality RCTs are necessary to investigate this further.
International Institute of Nutritional Sciences and Applied Food Safety Studies, University of Central Lancashire, Preston, UK.
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Warthon-Medina
Maternal and Infant Nutrition and Nurture Unit MAINN, University of Central Lancashire, Preston, UK.
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Moran
International Institute of Nutritional Sciences and Applied Food Safety Studies, University of Central Lancashire, Preston, UK.
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Stammers
International Institute of Nutritional Sciences and Applied Food Safety Studies, University of Central Lancashire, Preston, UK.
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Dillon
School of Psychology, University of Central Lancashire, Preston, UK.
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Qualter
1] Nutrition Research Group, Research Institute of Biomedical and Health Sciences, University of Las Palmas de Gran Canaria, Las Palmas de Gran Canaria, Spain [2] Ciber Obn Physiopathology of Obesity and Nutrition, Institute of Health "Carlos III", Madrid, Spain.
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Nissensohn
1] Nutrition Research Group, Research Institute of Biomedical and Health Sciences, University of Las Palmas de Gran Canaria, Las Palmas de Gran Canaria, Spain [2] Ciber Obn Physiopathology of Obesity and Nutrition, Institute of Health "Carlos III", Madrid, Spain.
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Serra-Majem
International Institute of Nutritional Sciences and Applied Food Safety Studies, University of Central Lancashire, Preston, UK.
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Lowe
D000369:Aged, 80 and over; D000375:Aging; D002657:Child Development; D002664:Child Nutritional Physiological Phenomena; D002675:Child, Preschool; D003071:Cognition; D003072:Cognition Disorders / Q000209:etiology / Q000517:prevention & control; D060825:Cognitive Dysfunction / Q000178:diet therapy / Q000517:prevention & control; D003677:Deficiency Diseases / Q000178:diet therapy / Q000517:prevention & control; D004032:Diet / Q000009:adverse effects; D019587:Dietary Supplements; D058620:Elder Nutritional Physiological Phenomena; D019317:Evidence-Based Medicine; D056344:Executive Function; D006801:Humans; D009048:Motor Skills; D055495:Neurogenesis; D009752:Nutritional Status; D015032:Zinc / Q000008:administration & dosage* / Q000172:deficiency / Q000627:therapeutic use
D015032:Zinc