Dietary index for gut microbiota and risk of incident irritable bowel syndrome: a large-scale prospective cohort study.

Background: The novel Dietary Index for Gut Microbiota (DI-GM) quantifies dietary patterns influencing microbiota health, yet its association with irritable bowel syndrome (IBS) risk remains unexplored. We aim to investigate prospective association of DI-GM with incident IBS in a long-term cohort.

Methods: Participants free of IBS at baseline with at least one record of 24-hour dietary recall from UK Biobank were included (N = 175,103). DI-GM was composed of 14 food/nutrient components known to influence gut microbial health. Each component was scored 0 or 1 based on sex-specific median intakes, and total scores were summed. The primary outcome was incident IBS. Multivariable Cox models were used to estimate associated risk.

Results: Over a 12.56-years of follow-up, 2,980 incident IBS cases were identified. Compared to participants with the lowest DI-GM quartile, those with the highest quartile had a 13% lower IBS risk (HR = 0.87; 95% CI: 0.79-0.97; P-value = 0.009), with significant trend (P-trend = 0.012). Moreover, per 1 score increase in DI-GM was associated with a 3% reduced IBS risk (HR = 0.97; 95% CI: 0.95-0.99; P-value = 0.009). Subgroup and sensitivity analyses consistently supported this inverse association.

Conclusions: Higher baseline DI-GM scores, reflecting dietary patterns supportive of gut microbiota, are associated with lower risk of developing IBS. These findings suggest that the DI-GM score may serve as a useful predictive tool for assessing IBS risk and facilitating the implementation of targeted dietary interventions. Future studies should examine changes in DI-GM scores over time help establish a potential causal link with IBS.