Low-FODMAP diet, rifaximin equally efficacious in IBS with diarrhoea

In patients with diarrhoea-predominant inflammatory bowel disease (IBS-D), a low FODMAP diet (LFD) intervention and rifaximin treatment both result in improved outcomes, as shown in a study.

The study included 65 adult patients with IBS-D. These patients were randomly assigned to undergo LFD or receive rifaximin for 5 weeks.

Changes in mean daily abdominal pain and bloating at week 5 were evaluated as the primary endpoints. Secondary endpoints included changes in IBS Symptom Severity Score (IBS-SSS) and Bristol Stool Form Scale (BSFS) at week 5. Exploratory analyses were also performed to determine the percentage of responders, defined as patients who achieved a ≥30-percent reduction in abdominal pain or bloating.

Stool samples were collected at baseline and weeks 2, 4, and 5 for 16S rRNA sequencing. Additionally, glucose breath testing was conducted at baseline and week 5.

At week 5, patients in both LFD and rifaximin groups had substantial reductions in abdominal pain (–0.29 vs –0.24 points per week, respectively), bloating (–0.29 vs -0.19 per week), and IBS-SSS (–14.2 vs –13.3 per week; p<0.0001 for all). There was no significant change observed in BSFS.

Breath test results were mixed in terms of predicting treatment response. For example, positive baseline hydrogen BT was associated with lower odds of rifaximin response, whereas methane conversion at week 5 showed inconsistent associations with rifaximin response.

Meanwhile, distinct baseline taxa were associated with treatment response. LFD response was associated with lower abundance of putative saccharolytic taxa (Butyricimonas, Bacteroides, Intestinibacter). On the other hand, rifaximin response correlated with an enrichment in taxa with putative short-chain fatty acid-producing and bile acid-modifying potential (Ruminococcus, Coprococcus, Odoribacter). Nonresponse was associated with an enrichment of putative proteolytic taxa (Bilophila, Alistipes, Prevotella).

More studies are needed to validate the findings before informing personalized treatment approaches.