To address this gap in knowledge, the Michigan Medicine researchers designed the first randomized controlled trial to compare the Mediterranean diet directly against another established therapeutic diet for IBS. In previous studies, the Mediterranean diet had typically been compared only to a participant’s regular, "typical" diet, which often lacked the rigor of a randomized controlled trial format.
In this pilot study, participants were randomized into two distinct groups. One group followed the Mediterranean diet, while the other followed the intensive restriction phase of the low FODMAP diet. The trial lasted for four weeks, a duration intended to capture the initial physiological response to the dietary shifts. All participants in the study had been clinically diagnosed with either IBS-D, where diarrhea is the predominant symptom, or IBS-M, which involves mixed symptoms of both constipation and diarrhea.
The researchers established a primary endpoint based on standards recognized by the Food and Drug Administration (FDA): a 30% reduction in the intensity of abdominal pain after the four-week period. This metric is considered a significant clinical marker for improvement in IBS trials.
The results of the study were encouraging for proponents of the Mediterranean diet. In the group following the Mediterranean eating pattern, 73% of patients met the primary endpoint for symptom improvement. In comparison, 81.8% of the patients in the low FODMAP group met the same endpoint. While the low FODMAP diet did result in a higher percentage of patients achieving relief and showed a greater overall improvement when measured by both abdominal pain intensity and a standardized IBS symptom severity score, the success rate of the Mediterranean diet was substantial enough to suggest it as a powerful tool for clinical use.
"Restrictive diets, such as low FODMAP, can be difficult for patients to adopt," explained Prashant Singh, MBBS, a gastroenterologist at Michigan Medicine and the lead author of the paper. Dr. Singh highlighted the practical barriers that often prevent patients from successfully managing their condition through diet alone. "In addition to the issue of being costly and time-consuming, there are concerns about nutrient deficiencies and disordered eating when trying a low FODMAP diet. The Mediterranean diet interested us as an alternative that is not an elimination diet and overcomes several of these limitations related to a low FODMAP diet."
The distinction between an elimination diet and an inclusive diet is critical in the context of long-term disease management. For a patient with IBS, the prospect of never eating garlic, onions, or certain fruits again can be daunting and socially isolating. The Mediterranean diet, by contrast, focuses on the quality and variety of whole foods, making it easier to follow in social settings and more sustainable over several years.
