Black CJ, Staudacher HM, Ford AC Efficacy of a low FODMAP diet in irritable bowel syndrome: systematic review and network meta-analysis. Gut. 2021 Aug 10. pii: gutjnl-2021-325214. doi: 10.1136/gutjnl-2021-325214.

OBJECTIVE: A diet low in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAP) is recommended for irritable bowel syndrome (IBS), if general lifestyle and dietary advice fails. However, although the impact of a low FODMAP diet on individual IBS symptoms has been examined in some randomised controlled trials (RCTs), there has been no recent systematic assessment, and individual trials have studied numerous alternative or control interventions, meaning the best comparator is unclear. We performed a network meta-analysis addressing these uncertainties.

DESIGN: We searched the medical literature through to 2 April 2021 to identify RCTs of a low FODMAP diet in IBS. Efficacy was judged using dichotomous assessment of improvement in global IBS symptoms or improvement in individual IBS symptoms, including abdominal pain, abdominal bloating or distension, and bowel habit. Data were pooled using a random effects model, with efficacy reported as pooled relative risks (RRs) with 95% CIs, and interventions ranked according to their P-score.

RESULTS: We identified 13 eligible RCTs (944 patients). Based on failure to achieve an improvement in global IBS symptoms, a low FODMAP diet ranked first vs habitual diet (RR of symptoms not improving=0.67; 95% CI 0.48 to 0.91, P-score=0.99), and was superior to all other interventions. Low FODMAP diet ranked first for abdominal pain severity, abdominal bloating or distension severity and bowel habit, although for the latter it was not superior to any other intervention. A low FODMAP diet was superior to British Dietetic Association (BDA)/National Institute for Health and Care Excellence (NICE) dietary advice for abdominal bloating or distension (RR=0.72; 95% CI 0.55 to 0.94). BDA/NICE dietary advice was not superior to any other intervention in any analysis.

CONCLUSION: In a network analysis, low FODMAP diet ranked first for all endpoints studied. However, most trials were based in secondary or tertiary care and did not study effects of FODMAP reintroduction and personalisation on symptoms.

Ratings by Clinicians (at least 3 per Specialty)
Specialty Score
Internal Medicine
Family Medicine (FM)/General Practice (GP)
General Internal Medicine-Primary Care(US)
Comments from MORE raters

Gastroenterology rater

This network meta-analysis shows that the low-FODMAP diet may be superior to other dietary interventions in reducing symptoms of irritable bowel syndrome, including abdominal bloating or distension. The study combines the results of 13 randomized controlled trials, conducted in Sweden, Australia, China, USA, United Kingdom, Thailand, or Iran, among other countries. I wonder to what extent all the studies applied the same FODMAP diet formulated with homogeneous criteria, or whether the different diets used in each cultural setting represented local consumption patterns that could be too much heterogeneous to be combined in a meta-analysis. This aspect prior to any meta-analysis was not addressed by the authors and I believe that this point is essential to interpret properly the results of this network meta-analysis.

Gastroenterology rater

IBS is a very difficult syndrome to manage. Patients do not have the same response to therapies and frustration often affects them after treatment failure. Low FODMAP diet is a frequently adopted srategy for IBS management. This meta-analysis supports with high-quality evidence about its usefulness.

General Internal Medicine-Primary Care(US) rater

The Fodmap Diet for IBS is worth a try. This interesting article demonstrates benefit from a low FODMAP diet. Whether all components of the diet are necessary is uncertain, but patients could reintroduce one at a time and see what works.

Internal Medicine rater

The studies had a short duration (3-6 weeks, only one of 3 months). Longer duration studies are needed in order to see the effect persistence. The second question is how difficult is it to maintain such a diet, comparing to the magnitude of effect.

Internal Medicine rater

Very good results for a simple intervention in this hard-to-treat condition.