- In a U.K. study of adults with irritable bowel syndrome (IBS), 62% of those on the Mediterranean diet achieved clinically significant symptom relief compared with 42% of those given traditional dietary advice.
- Those assigned the Mediterranean diet also reported more improvement on the IBS Symptom Severity Scale.
- The findings support the use of the Mediterranean diet as a first-line IBS therapy.
The Mediterranean diet outperformed traditional dietary advice for irritable bowel syndrome (IBS), challenging current recommendations for standard dietary counseling as a first-line therapy, a U.K. randomized clinical trial found.
Among 139 adults with IBS, 62% of those following a Mediterranean diet achieved clinically significant symptom relief (95% CI 50%-73%) compared with 42% of those given traditional dietary advice (95% CI 31%-55%), reported Imran Aziz, MD, MBChB, of the University of Sheffield in England, and colleagues in the Annals of Internal Medicine.
The difference in clinical response confirmed that the Mediterranean diet was not just non-inferior, but also superior to standard dietary counseling (P=0.017), they reported.
Also, the mean improvement on the IBS Symptom Severity Scale (IBS-SSS) also was greater with the Mediterranean diet (101.2 vs. 64.5 points, P=0.034).
“Clinicians could now offer [the Mediterranean diet] as an alternative first-line option” to traditional dietary advice, Aziz told MedPage Today in an email. “In practice, this would involve presenting both dietary approaches to patients during initial consultations, allowing them to choose based on their current eating habits, dietary preferences, and cultural context.”
Current guidance recommends traditional dietary advice as the first step, followed by the more complex low FODMAP (fermentable oligosaccharides, disaccharides, monosaccharides, and polyols) diet as a second-line therapy. Although the low FODMAP diet helps up to 70% of patients, it can negatively affect gut microbiota and is complex, restrictive, costly, and socially inconvenient for patients.
“Due to these challenges, the low FODMAP diet should be undertaken only through the supervision of a specialist dietitian or nutritionist, although this can be difficult to access and stretches busy healthcare systems,” the authors noted. “Hence, patients with IBS seek other dietary options.”
The findings largely align with prior studies that have “basically shown similar results — that it works for a certain proportion of patients,” Prashant Singh, MBBS, of the University of Michigan Medical School in Ann Arbor, told MedPage Today. Singh, who was not involved in the current research, led a 2025 study comparing the Mediterranean diet to the low FODMAP one.
The data from Aziz’s group helps make “us feel better about offering the Mediterranean diet for IBS patients because there is more [supporting] evidence, so you feel more confident about offering that choice to your patients,” he said.
The study’s primary endpoint was a reduction of 50 or more points in IBS-SSS score at 6 weeks. A secondary endpoint was a 100-or-more point drop. The Mediterranean diet achieved the latter in 44% of participants (95% CI 32%-57%) compared with 32.4% for traditional dietary advice (95% CI 22%-45%).
The frequency of abdominal pain improved significantly more in the Mediterranean diet group than those following traditional advice, with patients experiencing 1.2 fewer days of pain per 10-day period (95% CI -2.0 to -0.4).
The mechanism behind these benefits remains unclear, the investigators wrote, and includes a counterintuitive finding: The diet actually increased participants’ intake of oligosaccharides — fermentable carbohydrates known to produce gas and worsen IBS symptoms — yet patients still improved. This runs counter to the low FODMAP diet, which specifically restricts such compounds, and warrants further study, the authors wrote.
“We acknowledge this is counterintuitive and suggest there may be a specific or synergistic effect of the [Mediterranean diet] in beneficially regulating the microbiome-gut-brain axis, implying that the overall dietary pattern may override individual component effects,” Aziz said. “This doesn’t invalidate low FODMAP for non-responders but suggests the broader nutritional context matters significantly.”
The study enrolled 139 adults with IBS between October 2023 and December 2024 through an online platform. Participants (mean age 40.4, 80% women) were randomized to traditional dietary advice (n=71) or a Mediterranean diet (n=68). They self-reported dietary adherence every 2 weeks and completed baseline and 6-week assessments. Nineteen dropped out and another 10 were excluded for poor adherence, leaving 110 for per-protocol analysis.
Study limitations included the inability to blind participants, short follow-up, and exclusion of non-English speakers and those without internet access. Strengths included national recruitment, patient-led diet implementation after diet education, and real-world generalizability within a non-Mediterranean country.
