Among individuals with irritable bowel syndrome (IBS), the Mediterranean diet proved superior to established traditional dietary advice and achieved response rates comparable to those typically expected from the low fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAP) diet, according to a randomized trial.
“IBS patients rank dietary options as a top research priority, yet evidence-based choices are limited,” senior author Imran Aziz, MBChB, MD, a Consultant Gastroenterologist at the University of Sheffield, United Kingdom, told GI & Hepatology News. “Most patients receive traditional dietary advice as first-line therapy (with only 40% responding), with non-responders escalated to the complex, restrictive low FODMAP diet requiring specialist dietetic supervision. This study addresses whether the Mediterranean diet, which is easier to implement and has established broader health benefits, could serve as an effective first-line alternative.”
The study, published in the Annals of Internal Medicine, enrolled 139 adults across the United Kingdom who met Rome IV criteria for IBS and scored 75 or greater on the IBS Symptom Severity Scale (IBS-SSS). The researchers randomized participants 1:1 to 6 weeks of traditional dietary advice or the Mediterranean diet delivered via an online group education model, a pragmatic design reflecting real-world clinical practice. The primary endpoint was a 50-point or greater reduction on the IBS-SSS.
The researchers reported that 62% of participants assigned to the Mediterranean diet achieved the primary endpoint, compared with 42% receiving traditional dietary advice. The between-group difference favored the Mediterranean diet by 20%, demonstrating not only noninferiority but statistical superiority.
For the secondary endpoint of a 100-point or greater reduction on the IBS-SSS, response rates again numerically favored the Mediterranean die (44% vs. 32%), but this difference did not reach statistical significance. Mean improvement in IBS-SSS was significantly greater with the MD than with TDA (−101.2 vs. −64.5), with the largest separation appearing at the 6-week mark. Symptom improvements emerged early, with both groups showing significant reductions by week 2.
In other findings, both groups improved across IBS-SSS components of pain, bloating, bowel dissatisfaction, and interference with life. Only frequency of abdominal pain showed a statistically greater benefit with the Mediterranean diet. Measures of mood based on the Patient Health Questionnaire-4, somatic symptom burden based on the Patient Health Questionnaire-12, and quality of life based on the Short Form-8 Health Survey improved within groups but did not differ significantly between diets. Diet satisfaction was comparable between both groups.
The authors noted that the mechanism by which the Mediterranean diet alleviates IBS symptoms remains unclear. “Whether there is a specific or synergistic effect of the [Mediterranean diet] in beneficially regulating the microbiome–gut–brain axis warrants investigation,” they wrote. “For example, the [Mediterranean diet] positively affects the gut microbiome, and some of its ingredients, such as olive oil, possess anti-inflammatory and antioxidant properties, while also reducing visceral hypersensitivity in animal models.”
Aziz acknowledged certain limitations of the trial, including the inability to blind participants to their assigned diets, the 6-week duration which limits assessment of long-term benefits, and exclusion of those under 18 or over 65 years old. “The Mediterranean diet is widely available, culturally acceptable, and has numerous established health benefits,” he said. “This makes it an attractive first-line option for IBS that patients can implement without requiring specialist dietetic support.”
The researchers had no relevant disclosures.