Clinical trial: A Mediterranean diet is feasible and improves gastrointestinal and psychological symptoms in irritable bowel syndrome

Aliment Pharmacol Ther. 2023 Nov 15. doi: 10.1111/apt.17791. Online ahead of print.


Heidi M Staudacher 1Sophie Mahoney 1Kim Canale 1Rachelle S Opie 1Amy Loughman 1Daniel So 1 2Lauren Beswick 3 4Chris Hair 3 4Felice N Jacka 1 5


Author information

1Food & Mood Centre, The Institute for Mental and Physical Health and Clinical Translation (IMPACT), School of Medicine and Barwon Health, Deakin University, Geelong, Victoria, Australia.

2Department of Nutritional Sciences, King's College London, London, UK.

3Department of Gastroenterology, Barwon Health, Geelong, Victoria, Australia.

4School of Medicine, Deakin University, Geelong, Victoria, Australia.

5Centre for Adolescent Health, Murdoch Children's Research Institute, Parkville, Victoria, Australia.


Background: Diet is fundamental to the care of irritable bowel syndrome (IBS). However, some approaches are not appropriate for individuals experiencing psychological symptoms.

Aims: To assess feasibility of a Mediterranean diet in IBS and its impact on gastrointestinal and psychological symptoms.

Methods: We recruited adults with Rome IV IBS and mild or moderate anxiety and/or depressive symptoms to an unblinded 6-week randomised controlled trial. Patients were randomised to Mediterranean diet counselling or habitual diet. We collected gastrointestinal and psychological symptom data, dietary data and stool samples for metagenomic sequencing.

Results: We randomised 59 individuals (29 Mediterranean diet, 30 control); 48 completed the study. The Mediterranean Diet Adherence Screener score was higher in the Mediterranean diet group than controls at week 6 (7.5 [95% CI: 6.9-8.0] vs. 5.7 [5.2-6.3], p < 0.001), and there was a greater score increase than controls (2.1 [95% CI: 1.3-2.9] vs. 0.5 [95% CI: 0.1-1.0], p = 0.004), demonstrating Mediterranean diet feasibility. There was a greater proportion of gastrointestinal symptom responders in the Mediterranean diet group than controls (24/29, 83% vs. 11/30, 37%, p < 0.001) and depression responders (15/29, 52% vs. 6/30 20%, p = 0.015). There was no difference in FODMAP intake at week 6 (p = 0.51). Gastrointestinal adverse events were similar (p = 0.588). There were no differences in change in microbiome parameters between groups.

Conclusions: A Mediterranean diet is feasible in IBS and leads to improvement in gastrointestinal and psychological symptoms. Although this study was unblinded, these findings together with the broader benefits of the Mediterranean diet, provide strong impetus for future research in IBS. Australia New Zealand Clinical Trials Registry: ACTRN12620001362987.

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