Association between zinc intake and risk of digestive tract cancers: A systematic review and meta-analysis

Background & aims: Association between zinc intake and digestive tract cancers risk has been reported in several epidemiological studies, while the results were controversial. The aim of our study was to get a systemic review of this issue. Methods: PUBMED and EMBASE were searched up to April 2013, supplemented with manual-screening for relevant articles. Two independent reviewers independently extracted data from eligible studies, risk ratio (RR) or odds ratio (OR) with 95% CIs for the highest versus lowest categories of zinc intake was adopted. Either a fixed- or a random-effects model was adopted to estimate overall odds ratios. Besides, dose response, subgroup, and publication bias analyses were applied. Results: Nineteen studies with approximately 400,000 participants were included in this meta-analysis. The pooled relative risk (RR) of overall digestive tract cancers for the highest versus lowest categories of zinc intake was 0.82 (95% Cl: 0.70-0.96; p = 0.013). Comparing the highest with lowest categories, higher zinc intake was significantly associated with reduced colorectal cancer risk (pooled RR = 0.80, 95% CI: 0.70-0.92; p = 0.002), while zinc intake was not statistically associated with gastric cancer risk (pooled RR = 0.91, 95% Cl: 0.64-1.29; p = 0.581) or esophageal cancer risk (pooled RR = 0.72, 95% Cl: 0.44-1.17; p = 0.187). However, subgroup analyses showed that zinc intake was significantly associated with esophageal cancer risk and gastric cancer risk in Asia, but not in America and Europe. Conclusions: Dietary zinc intake was inversely associated with digestive tract cancers, especially colorectal cancer risk in this study. (C) 2013 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved.