Intake of fruit and vegetables and risk of esophageal squamous cell carcinoma: a meta-analysis of observational studies.

Quantification of the association between the intake of fruit and vegetables and risk of esophageal squamous cell carcinoma (ESCC) is controversial even though several studies have explored this association. We summarized the evidence from observational studies in categorical, linear and non-linear dose-response meta-analyses. Eligible studies published up to 31 July 2012 were retrieved via computer searches of MEDLINE and EMBASE as well as manual review of references. Random-effects models were used to calculate summary relative risks (SRRs) and the corresponding 95% confidence intervals (CIs). A total of 32 studies involving 10,037 cases of ESCC were included in this meta-analysis. The SRRs for the highest vs. lowest intake were 0.56 (95% CI: 0.45-0.69) for vegetable intake and 0.53 (95% CI: 0.44-0.64) for fruit intake (pheterogeneity <0.001 for both). Similar results were observed in a linear dose-response analysis. There was evidence of non-linear associations for intakes of fruit (pnon-linearity <0.001) and vegetables (pnon-linearity =0.041). There was no evidence of publication bias. These data support the hypothesis that intakes of vegetables and fruit may significantly reduce the risk of ESCC. Further investigation with prospective designs, validated questionnaires and good control of important confounders is warranted.