Fecal Microbiota Transplantation Combined with a Low FODMAP Diet for the Treatment of Irritable Bowel Syndrome with Predominant Diarrhea

BACKGROUND: Fecal microbiota transplantation (FMT) has been found to be effective in irritable bowel syndrome with predominant diarrhea (IBS-D). We conducted this study to determine the impact of a low FODMAP diet (LFD) on the gut microbiota and the efficacy of FMT in the treatment of IBS-D. METHODS: A retrospective analysis of a single-arm open-label prospective study was conducted to investigate the impact of FMT alone (n = 40) and FMT+LFD (n = 40) in refractory IBS-D. The IBS-quality of life (QOL), IBS-severity scoring system (SSS), gastrointestinal symptom rating scale (GSRS), Hamilton anxiety scale (HAMA), and Hamilton depression scale (HAMD) were used to evaluate the efficacy, and partial 16S rDNA amplicon sequencing was used to profile the microbiota. RESULTS: The response rates were higher in the FMT+LFD group than in the FMT group (1 mo, 3 mo, 6 mo: 70.0% vs. 55.0%, 67.5% vs. 57.5%, 62.5% vs. 27.5%, respectively). The FMT+LFD group showed significantly better improvement in IBS-QOL at 1, 3, and 6 months; IBS-SSS at 6 months; and GSRS at 1 month compared to FMT alone. Changes in HAMA and HAMD were similar in the two groups. The LFD significantly upregulated the FMT-induced microbial diversity (OTUs: 666 vs. 574, Adonis: P = 0.02) and significantly strengthened the upregulation of Bacteroides, Alistipes, and Ruminococcaceae_UCG-002 and the downregulation of Bifidobacterium. CONCLUSION: An LFD enhanced the efficacy of FMT, increased the gut microbial diversity after FMT, and strengthened the inhibitory effect of FMT on conditional pathogens.