Citrus fruit intake and the risk of nasopharyngeal carcinoma

Background and Objectives: Citrus fruit are suggested to be associated with reduced risk of nasopharyngeal carcinoma (NPC), but findings from epidemiologic studies have been inconsistent. We aimed to synthesize the association by conducting a meta-analysis of existing evidence. Methods and Study Design: Databases including Medline, EMBASE, Web of science, and the Cochrane Library were searched for eligible studies up to March 2019 using a series comprehensive searching terms. The adjusted odds ratios (ORs) of citrus fruit intake with NPC risk from each study were extracted to calculate a pooled association estimate with its 95% confidence interval (CI). Results: Nine studies totaling 3304 cases and 3850 controls were included in this analysis. Citrus fruit intake was significantly associated with reduced risk of NPC (OR: 0.72, 95% CI 0.58-0.91, p=0.005). In addition, this association tended to be stronger in Chinese (OR: 0.67, 95% CI 0.54-0.84, p<0.001). Dose-response analysis using cubic splines showed the risk of NPC decreased by 21% for citrus fruit intake of 4 times/week (OR: 0.79, 95% CI 0.66-0.94).