Introduction: There is a lack of data on the efficacy of dietary therapies by IBS subtype (IBS-D, IBS-C, and IBS-M). In a multi-center, double-blind trial, we recently showed that an experimental diet based on a novel discriminatory p-value-based IgG assay was superior to a sham diet in IBS patients. In the current analysis, we evaluated the efficacy of the IgG assay-guided experimental diet compared to a sham diet among IBS subtypes.

Methods: Adults with IBS (Rome IV) were enrolled from 6 centers. Patients who tested positive ≥1 food with the 18-food IgG assay (inFoods® IBS ELISA, Biomerica, CA) and who reported an average daily IBS abdominal pain intensity (API) score (0-10) between ≥3 to ≤7.5 during a 2-week baseline period were randomized to either an experimental or sham diet for 8 weeks. Patients on the experimental diet were instructed to eliminate foods for which they tested positive, while patients on the sham diet were instructed to eliminate foods for which they tested negative. The sham diet was balanced with the treatment diet for the number of foods, quantity consumed, and groups (i.e., cereals, vegetables) of eliminated foods. Daily assessments included API, bloating, and bowel habits. Weekly assessments included IBS Adequate Relief (AR), and Subject Global Assessment of Relief (SGA). Linear mixed and logistic regression modeling of endpoints in the intent-to-treat (ITT) population is presented for the three IBS subtypes and non-IBS-D (IBS-C+M) patients.

Results: 223 IBS patients (IBS-C = 80, IBS-M = 69, and IBS-D=74) were included. A higher proportion of IBS-C and IBS-M patients receiving the experimental diet met the primary endpoint for IBS-API (30% decrease in IBS-API) for ≥ 2 of the last 4 weeks compared to patients receiving the sham diet (67.1% vs. 35.8%, P=0.03 and 66% vs. 29.5%, P=0.015 respectively) (Figure 1). IBS-C patients on the experimental diet also had a significantly higher decrease in mean IBS-API, and SGA scores than IBS-C patients on the sham diet (P=0.03, and 0.01 respectively) (Table 1). IBS-M patients on the experimental diet met the IBS-API primary endpoint (p=0.0154) and a numerical improvement in bloating and SGA scores (p=0.053 and p=0.09, respectively) compared to the sham diet. Non-IBS-D patients on the experimental diet met the primary endpoint IBS-API and IBS-SSS (P=0.002, and p=0.045 respectively).

Conclusion: Among patients with IBS-C and IBS-M, an experimental elimination diet based on the results from the novel discriminatory -p-value-based IgG assay was superior to a sham diet across multiple endpoints and could pave the way to a more personalized approach to dietary therapy in patients with IBS.

Will Takakura

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