We thank Dr Hopayian for his thoughtful letter discussing our recent article dealing with the management of irritable bowel syndrome (IBS).1 In the network meta-analysis he refers to, there were 24 randomised controlled trials (RCTs), containing 1803 patients, comparing a diet low in FODMAPs with either habitual diet, sham dietary intervention, or another active whole dietary intervention.2 This compares with only two trials of a Mediterranean diet, recruiting 85 patients, although another RCT of a Mediterranean diet in 139 patients with IBS has been published since the network meta-analysis was conducted.3
In the network meta-analysis,2 in terms of global symptom improvement, a starch- and sucrose-reduced diet ranked first, a gluten-free diet second, and a tritordeum-based diet third, but these interventions were each studied in only one or two RCTs. A low-FODMAP diet ranked fourth in the network (RR of IBS symptoms not improving = 0.51; 95% CI = 0.37 to 0.70). The Mediterranean diet was not superior to any of the control interventions or any of the other active dietary interventions. Finally, there were no data on the effect on quality of life scores reported.
In terms of endpoints studied in dietary intervention trials in IBS, all RCTs in the network meta-analysis reported the effect of the intervention on global symptoms rather than on constipation, pain, or bloating separately.2 Most trials used either adequate relief of symptoms or an improvement on the IBS severity scoring system,4 a validated questionnaire. Both are widely accepted as endpoints in treatment trials in IBS. In terms of the bowel habit of participants in these RCTs, 17 of the 28 eligible trials recruited patients with a mixed bowel habit among their participants, although the effect of dietary interventions by specific bowel habit was not reported by many.
In terms of the evidence, there was moderate certainty in the network meta-analysis that a low-FODMAP diet was superior to habitual diet for global IBS symptoms.2 All other comparisons across the network were rated low or very low confidence. Hence, the best evidence exists for the use of a low-FODMAP diet, although care is needed with its implementation because of the high levels of restrictive eating behaviours seen in patients with IBS.5 It should, therefore, only be implemented by a FODMAP-accredited dietitian who can assess for red flags, in the context of restrictive diets, and monitor nutritional adequacy.
- © British Journal of General Practice 2026
References
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