The relationship between zinc intake and indices of cognitive function: A systematic review and meta-analyses

Abstract

.The databases searched included MEDLINE, EMBASE (both on Ovid) and the Cochrane Library CENTRAL from inception to March2013. Following the EURRECA protocol of screening and sorting, 2173 studies were assessed for eligibility criteria. Data was extractedfrom 19 studies across all population groups that met the inclusion and exclusion criteria (12 randomised controlled trials (RCTs), and7 observational studies). Meta-analysis of data extracted from 7 RCTs conducted in children was undertaken using Review Manager (5.2).A random effects model was used to investigate the impact of zinc intake on indices of cognitive function including intelligence (7 datasets from 862 children), executive function (7 data sets from a 942 children), and motor development (4 data sets from 622 children).The analysis yielded a pooled standard mean difference for the impact of zinc supplementation on intelligence of 0.06 (95% CI - 0.10,0.22) p = 0.47; executive function, 0.13 (95% CI, - 0.02, 029) p = 0.10 and motor development, - 0.05 (95% CI - 0.36, 0.26) p = 0.75.These results revealed that there was no signiÞcant overall effect of zinc supplementation on these cognitive function outcomes assessedin children.Due to the heterogeneity of the cognitive function test methodology, only a small number of studies could be included in the meta-analysis. To date, the evidence regarding the effect of zinc intake on cognitive function remains inconclusive. However, taking all thestudies per population as a whole there is some evidence for a positive association between zinc and cognitive function and there is a needfor further high quality RCTs to investigate this relationship.