Introduction
Inflammatory bowel disease (IBD) represents a growing global health burden, with rising incidence across both Western and developing countries. Environmental and lifestyle factors, particularly dietary patterns, are increasingly recognized as important contributors to disease pathogenesis. Plant-based dietary patterns rich in fiber, antioxidants, and anti-inflammatory nutrients may influence gut microbiota composition and immune regulation, thereby modifying IBD risk. The Healthy Plant-Based Diet Index (hPDI), which emphasizes intake of fruits, vegetables, whole grains, legumes, nuts, and other healthful plant foods while limiting less healthy plant and animal products, has been associated with reduced risk of several chronic inflammatory conditions. However, the relationship between adherence to hPDI and incident IBD remains incompletely defined, with inconsistent findings across observational studies. We therefore conducted a systematic review and meta-analysis to evaluate the association between adherence to a healthy plant-based dietary pattern and risk of developing IBD.
Aims & Methods
A systematic literature search of PubMed was performed according to PRISMA guidelines to identify cohort studies evaluating associations between hPDI adherence and incident IBD. Eligible studies reported hazard ratios (HRs) with corresponding 95% confidence intervals (CIs). Data were pooled using random-effects meta-analysis models to account for between-study variability. Heterogeneity was assessed using subgroup and sensitivity analyses, including evaluation based on hPDI categorization (tertiles versus quartiles/quintiles). Publication bias was evaluated using funnel plot visualization, Begg’s and Egger’s tests, and leave-one-out sensitivity analyses. Statistical analyses were conducted using STATA version 15.1.
Results
Among 45 identified records, eight cohort datasets from four eligible studies met inclusion criteria. Higher adherence to hPDI was associated with a significantly reduced risk of developing IBD (pooled HR = 0.82; 95% CI: 0.74 - 0.89). Substantial variation in effect estimates was explained by differences in dietary exposure categorization. Studies comparing the highest versus lowest quartile or quintile of hPDI demonstrated a strong protective association (HR = 0.70; 95% CI: 0.59 - 0.80), whereas analyses using tertile-based categorization did not show a statistically significant association (HR = 0.95; 95% CI: 0.84 - 1.06). No evidence of publication bias was identified (Egger’s test p = 0.624; Begg’s test p = 0.805). Sensitivity analyses confirmed the robustness and stability of pooled estimates, with no single study disproportionately influencing results.
Conclusion
Greater adherence to a healthy plant-based dietary pattern is associated with a significantly lower risk of incident IBD. These findings support the hypothesis that diet-mediated modulation of intestinal inflammation may play an important role in disease prevention. The stronger protective effect observed with higher-resolution dietary categorization suggests a dose response relationship between plant-based diet quality and IBD risk. Promotion of healthful plant-forward dietary patterns may represent a feasible population level strategy for primary prevention of IBD. Future prospective and mechanistic studies are needed to clarify causal pathways and identify dietary components most strongly associated with protective effects.
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