Inflammatory, antioxidant, and gut microbiota-related dietary indices and gastric cancer risk: a case-control study

Dietary patterns may influence gastric carcinogenesis through inflammatory, oxidative, intestinal permeability, and gut microbiota-related pathways. However, comprehensive studies simultaneously evaluating inflammatory, antioxidant, and microbiota-oriented dietary indices together with multiple biological biomarkers in gastric cancer remain limited.

This case-control study included 960 adults comprising 480 patients with histologically confirmed gastric cancer and 480 control participants. Dietary intake was assessed using a validated food frequency questionnaire. The Dietary Inflammatory Index (DII), Composite Dietary Antioxidant Index (CDAI), and Dietary Index for Gut Microbiota (DI-GM) were calculated and categorized into tertiles. Inflammatory, oxidative stress, intestinal permeability, and microbiota-related biomarkers were measured using standardized laboratory methods. Multivariable logistic regression analyses were performed to evaluate associations between dietary indices and gastric cancer risk.

Patients with gastric cancer had significantly higher DII scores and significantly lower CDAI and DI-GM scores compared with controls (all p < 0.001). In fully adjusted models, participants in the highest DII tertile had substantially greater odds of gastric cancer (OR: 6.21; 95% CI: 4.39-8.79), whereas higher CDAI (OR: 0.20; 95% CI: 0.14-0.28) and DI-GM (OR: 0.25; 95% CI: 0.18-0.35) were inversely associated with disease risk (all P-trend < 0.001). DII showed positive correlations with inflammatory and oxidative biomarkers, including CRP, TNF-α, MDA, zonulin, and NLR. However, the biomarker differences across dietary-index tertiles were generally modest. Among gastric cancer cases, DI-GM tertiles were significantly associated with zonulin concentrations. ROC analyses demonstrated moderate discriminatory performance for DII (AUC: 0.712), CDAI (AUC: 0.688), and DI-GM (AUC: 0.631).

In conclusion, proinflammatory dietary patterns were associated with greater odds of gastric cancer, whereas diets rich in antioxidants or supportive of gut microbiota showed inverse associations. These associations were accompanied by differences in inflammatory, oxidative stress, intestinal permeability, and microbial metabolism related biomarkers. However, due to the case-control design, causality cannot be inferred, and the findings should be considered associational rather than causal.