Associations of dietary carbohydrate and salt consumption with esophageal cancer risk: a systematic review and meta-analysis of observational studies

Evidence has shown that essential nutrients are highly correlated with the occurrence of esophageal cancer (EC). However, findings from observational studies on the associations between dietary carbohydrate, salt consumption, and the risk of EC remain controversial.The aim of this study was to conduct a systematic review and meta-analysis to confirm the associations of dietary carbohydrate and salt consumption with EC risk.Various electronic databases (PubMed, MEDLINE, Embase, Google Scholar, Cochrane Library, Chinese Electronic Periodical Services, and China Knowledge Resource Integrated) were searched up until January 31, 2019.Data related to patient characteristics and study characteristics were extracted by 2 independent reviewers. The risk ratio reported as relative risk (RR) or odds ratio (OR) was extracted, and random-effects models were performed to estimate the summary risk ratio.In total, 26 studies were included in this analysis, of which 12 studies, including 11 case-control studies and 1 cohort study, examined dietary carbohydrates, and 18 studies, including 16 case-control studies and 2 cohort studies, examined dietary salt. The pooled OR showed that dietary carbohydrate intake was inversely related to EC risk (OR = 0.62; 95% confidence interval [CI], 0.50-0.77), but positive correlations between dietary salt intake and the risk of EC were supported by the recruited case-control studies (OR = 1.97; 95% CI, 1.50-2.61) and cohort studies (RR = 1.04; 95% CI, 1.00-1.08).Salt is an essential nutrient for body functions and biochemical processes. Providing health education and management regarding proper use of salt in daily foods and labeling the amount of sodium in manufactured products to reduce the risk of developing EC should be more appropriately performed in the general population.