Lower Serum Zinc Concentration Despite Higher Dietary Zinc Intake in Athletes: A Systematic Review and Meta-analysis
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SYSTEMATIC REVIEW
Lower Serum Zinc Concentration Despite Higher Dietary Zinc Intake in Athletes: A Systematic Review and Meta-analysis Anna Chu1 • Cushla Holdaway1 • Trishala Varma1 • Peter Petocz2 Samir Samman1,3
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Ó Springer International Publishing AG, part of Springer Nature 2017
Abstract Background Zinc is an essential trace element that has been implicated in numerous biological functions, including immunity, energy metabolism and antioxidative processes. Recent evaluations of the literature have provided evidence of significant acute changes in zinc metabolism following a bout of aerobic exercise. Objective The aim of this study was to determine the zinc status of trained athletes compared with control populations, as described in cross-sectional studies. Design We conducted a systematic literature search of the PubMed, Scopus, SPORTDiscus and Cochrane Library electronic databases from inception to 28 January 2016 to identify cross-sectional studies that determined the zinc status of athletes compared with a control population.
Meta-analysis of the differences in serum zinc concentration and dietary zinc intake between groups were conducted. Results Twelve studies were included in the systematic review. Of the included studies, nine and eight studies provided sufficient data for the meta-analysis of serum zinc concentration and dietary zinc intake, respectively. Serum zinc concentration was significantly lower in athletes [- 0.93 lmol/L, 95% confidence interval (CI) - 1.62 to - 0.23] despite significantly higher dietary zinc intake compared with the control population (2.57 mg/day, 95% CI 0.97–4.16). Data on erythrocyte and urinary zinc from the included studies were insufficient for meta-analysis. Conclusions Despite higher total dietary zinc intake, athletes generally have lower serum zinc concentration, which suggests that athletes have higher requirement of zinc than those who are physically inactive. Further investigations of zinc metabolism during exercise and dietary zinc requirement in active populations are needed to establish evidence-based recommendations.
Key Points Electronic supplementary material The online version of this article (https://doi.org/10.1007/s40279-017-0818-8) contains supplementary material, which is available to authorized users. & Samir Samman [email protected] 1
Department of Human Nutrition, University of Otago, PO Box 56, Dunedin 9054, New Zealand
2
Department of Statistics, Macquarie University, Sydney, NSW 2109, Australia
3
School of Life and Environmental Sciences, University of Sydney, Sydney, NSW 2006, Australia
Athletes appear to be at risk of suboptimal zinc status, despite higher consumption of dietary zinc compared with controls. The discrepancies between dietary zinc intake and markers of zinc status may be indicative of altered zinc metabolism in athletes. Further studies are required to establish evidencebased clinical recommendations regarding dietary zinc intake in physically active populations.
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1 Introduction
2 Method
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