Research Summary

Mediterranean Low-FODMAP Diet Superior to NICE Guidance for Non-Constipation IBS in Randomized Trial

Edited by:
Anthony Calabro, MA

Key Highlights

  • Mediterranean-style low-FODMAP diet (MED–LFD) resulted in greater reductions in IBS Symptoms Severity Score (IBS-SSS) than NICE guidance at first follow-up and at 6 months.
  • Responder rates (≥50-point IBS-SSS reduction) were significantly higher with MED–LFD in both intention-to-treat and per-protocol analyses.
  • Improvements in quality of life, anxiety, depression, and stool form favored MED–LFD.

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A randomized controlled parallel-group trial demonstrated that a Mediterranean version of a low-FODMAP (Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols) diet (MED–LFD) was superior to NICE dietary recommendations for managing irritable bowel syndrome (IBS) without constipation. The findings, published in Nutrients, showed sustained improvements in symptom severity and quality of life through 6 months.

Investigators enrolled 108 adults aged 18 to 65 years with Rome IV non-constipation IBS and baseline IBS-SSS >175, consistent with at least moderate symptom severity. Participants were randomized 1:1 to MED–LFD (n = 54) or a NICE-guidance–based weekly dietary plan (n = 54). Assessments were conducted at baseline, first follow-up (4 weeks after NICE initiation and at completion of MED–LFD reintroduction), and at 6 months. The primary endpoints were change in IBS-SSS and responder rate, defined as a ≥50-point reduction. Secondary endpoints included symptom burden (GSRS-IBS), quality of life (IBS-QoL; SF-12), anxiety and depression (HADS), stool form (Bristol Stool Form Scale), adequate relief, adherence, and safety. A subset of 40 participants underwent stool volatile compound analysis using gas chromatography/mass spectrometry.

Study Findings

Symptom severity improved in both groups, with significantly greater reductions in the MED–LFD arm. In per-protocol analyses, IBS-SSS scores favored MED–LFD at the first follow-up (159 ± 80 vs 253 ± 94; P < .001) and at 6 months (168 ± 117 vs 245 ± 98; P = .001).

Responder rates were consistently higher with MED–LFD. In intention-to-treat analyses, 81.5% of MED–LFD participants vs 57.4% of NICE participants achieved a ≥50-point reduction at first follow-up (P = .007); at 6 months, rates were 70.4% vs 42.6% (P = .004). Per-protocol responder rates were 84.6% vs 60.8% at first follow-up (P = .007) and 79.2% vs 52.3% at 6 months (P = .006). In multivariable analysis, assignment to MED–LFD was the strongest independent predictor of response (first follow-up OR, 6.66; 95% CI, 1.46-30.4; second follow-up OR, 4.85; 95% CI, 1.31-17.96).

Secondary endpoints also favored MED–LFD. Improvements in GSRS-IBS, IBS-QoL total and subscales, SF-12, and HADS scores were greater in the MED–LFD group at both time points, as detailed in the study tables. Stool form normalized more frequently in the MED–LFD arm, with a higher proportion achieving Bristol Stool Form Scale types 3–5 at first follow-up (84.62% vs 60.78%; P = .023) and at 6 months (81.25% vs 61.36%; P = .021).

Adherence was higher with MED–LFD (first follow-up: 75% vs 41%; second follow-up: 45% vs 7%; both P < .001). No serious adverse events occurred; adverse events were reported in both groups without treatment discontinuations due to adverse effects.

In the exploratory subgroup, total stool short-chain and branched-chain fatty acid concentrations decreased from baseline in both groups at both follow-ups. The authors observed a polynomial association between changes in IBS-SSS and changes in volatile compound levels from baseline to first follow-up.

Clinical Implications

The authors concluded that integrating Mediterranean dietary elements into a structured low-FODMAP intervention was more effective than NICE guidance for improving symptoms and quality of life in adults with non-constipation IBS, with benefits sustained for at least 6 months and no serious safety concerns. They noted that further research is needed to determine whether stool volatile compounds may serve as objective markers of dietary response.

Expert Commentary

“Our randomized controlled parallel-group design study demonstrated that our innovative dietetic intervention, a low-FODMAP diet with components of the Mediterranean diet, is superior to the NICE recommendations for the management of symptoms of IBS without constipation,” the researchers concluded.

Reference
Kasti AN, Katsas K, Pavlidis DE, et al. Clinical trial: A Mediterranean low-FODMAP diet alleviates symptoms of non-constipation IBS-randomized controlled study and volatomics analysis. Nutrients. 2025;17(9):1545. Published April 30, 2025. doi:10.3390/nu17091545.