Rifaximin and Low FODMAP Diet Provide Comparable Symptom Relief in IBS-D: Study
USA: Researchers have found in a randomized trial that both rifaximin and a low FODMAP diet provide similar improvement in symptoms for patients with Irritable Bowel Syndrome with Diarrhea, suggesting either approach can be an effective treatment option.
A new study published in Clinical Gastroenterology and Hepatology by Allen Lee and colleagues from the University of Michigan provides fresh insight into how these two commonly used therapies compare, while also exploring whether gut microbiome patterns can help predict which patients are more likely to benefit. Irritable Bowel Syndrome with diarrhea (IBS-D) remains a challenging condition to manage, with fewer than half of patients responding to currently available treatments, prompting the need for more targeted strategies.
For this purpose, the researchers conducted a randomized controlled trial involving 65 adults diagnosed with IBS-D. Participants were assigned to receive either a low FODMAP diet or rifaximin therapy for five weeks. The primary outcomes focused on changes in daily abdominal pain and bloating, while secondary measures included the IBS Symptom Severity Score (IBS-SSS) and stool consistency assessed using the Bristol Stool Form Scale.
The trial revealed the following findings:
- Both the low FODMAP diet and rifaximin resulted in significant and similar reductions in abdominal pain and bloating during the study period.
- IBS Symptom Severity Score improved in both groups, reflecting an overall decrease in symptom burden.
- There was no meaningful change in stool consistency in either group, indicating bowel habits remained largely unchanged despite symptom relief.
- Breath testing showed inconsistent values in predicting treatment response.
- A positive baseline hydrogen breath test was associated with a lower likelihood of responding to rifaximin.
- Changes in methane levels demonstrated mixed and inconclusive associations with treatment outcomes.
- Overall, breath testing alone may not be a reliable predictor for guiding treatment decisions in IBS-D.
- Gut microbiome analysis provided more informative insights into treatment response.
- Responders to the low FODMAP diet had lower baseline levels of saccharolytic (carbohydrate-fermenting) bacteria.
- Responders to rifaximin showed higher abundance of microbes linked to short-chain fatty acid production and bile acid metabolism.
- Non-responders to both interventions had increased levels of proteolytic (protein-fermenting) bacteria.
These microbiome-related differences underscore the potential for utilizing gut microbial profiles to inform personalized treatment strategies in the future. However, the authors caution that these findings are preliminary and require further validation in larger cohorts before being applied in routine clinical practice.
Overall, the study confirms that both rifaximin and dietary modification, particularly through a low FODMAP approach, are viable options for managing IBS-D symptoms. At the same time, it opens the door to more individualized care by suggesting that microbial signatures could eventually help clinicians match patients with the most effective therapy.
Reference:
Lee, A., Rao, K., Singh, P., Fehlman, J., Gao, J., Takakura, W., Lynett, A., Haller, E., Ball, S., Marand, A., Liu, A., Shah, E., Menees, S., Punglia, R., Nojkov, B., Eswaran, S., Baker, J., Chey, W. D., Owyang, C., . . . Hasler, W. L. (2026). A Randomized Trial of Rifaximin vs Low FODMAP Diet for Symptom Outcomes and Microbiome Changes in Irritable Bowel Syndrome. Clinical Gastroenterology and Hepatology. https://doi.org/10.1016/j.cgh.2026.04.014
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