Dietary inflammatory index and risk of major digestive tract cancers: a GRADE-assessed systematic review and dose-response meta-analysis.

BACKGROUND & AIMS: Gastrointestinal (GI) cancers are an umbrella term for a group of malignant tumors that affect the digestive system. This systematic review and meta-analysis aimed to evaluate the association between the Dietary Inflammatory Index (DII) and the risk of GI cancers by synthesizing evidence from observational studies. METHODS: PubMed, Scopus, and Web of Science were searched using terms related to GI cancers and DII. A total of 52 observational studies (18 cohort, 34 case-control) were analyzed. Random or fixed effects meta-analyses were conducted to pool risk ratio (RR) for the highest vs. the lowest DII categories, with dose-response analyses performed where feasible. Quality was assessed via the Risk of Bias in Non-randomised Studies of Exposures tool. Evidence certainty was graded using the GRADE framework. RESULTS: Higher DII scores (pro-inflammatory diets) were significantly associated with increased risks of colorectal (RR 1.16, 95% confidence interval [CI] 1.04–1.29), colon (RR 1.12, 95% CI 1.11–1.33), and rectal cancers (RR 1.25, 95% CI 1.07–1.47) in cohort studies. No significant associations were found for gastric or pancreatic cancers in cohort studies. Case-control studies showed stronger associations for oral (RR 2.46), esophageal (RR 2.63), and pancreatic cancers (RR 2.57). CONCLUSION: The findings highlight the importance of dietary modifications to reduce inflammation for cancer prevention. Further prospective studies are needed to clarify causal relationships and refine dietary recommendations. SYSTEMATIC REVIEW REGISTRATION: PROSPERO registration no. CRD42023484691.