Low FODMAP diet significantly improves IBS symptoms: an Irish retrospective cohort study



There is growing evidence that a diet low in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAP) improves symptoms in irritable bowel syndrome (IBS) patients. We aimed to retrospectively investigate the effects of this diet in Irish IBS cohort over a 12-month follow-up period, including after re-introduction of the high FODMAP foods.


All the tertiary referrals seen by an FODMAP-trained dietician were reviewed (2013–2016). Patients were evaluated for IBS symptoms by a questionnaire (four-point Likert scale). Subsequently, advice regarding the low FODMAP diet was given. Symptoms’ response was assessed at 3-, 6-, and 12-month follow-up, by use of the same questionnaire. Re-introduction of high FODMAP foods was aimed to commence at the subsequent follow-up.


A total of 164 patients were identified. Thirty-seven patients were excluded due to failure to attend for follow-up. Hundred and twenty-seven patients (77% patients, of which 85% were female) completed the initial 3-month follow-up. Forty-five percent (74/164) and twenty-five percent (41/164) of the patients had continued follow-up at 6 and 12 months, respectively. Of the 127 patients who returned for follow-up, their commonest baseline symptoms were lethargy (92%), bloating (91%), flatulence (91%), and abdominal pain (89%). All symptoms were significantly improved at the initial follow-up (p < 0.0001 for all). Most patients (66%) were satisfied with their overall symptoms control. In patients who had a longer follow-up duration, all symptoms remained significantly improved compared to the baseline (p < 0.0001 for combined symptoms at 6 and 12 months). After re-introduction of the high FODMAP foods, all patients maintained their symptomatic response (n = 14/14 and n = 7/7 at 6- and 12-month follow-up, respectively). The best symptoms’ improvement was seen in those who were fully adherent to the FODMAP diet.


In this Irish retrospective cohort study, the low FODMAP diet significantly improved all IBS symptoms at 3-, 6-, and 12-month follow-up. Following the re-introduction of the high FODMAP foods in a subgroup of patients, they were able to maintain their long-term symptomatic response up to 9 months. The low FODMAP diet might be continued for longer than 3 months; however, further studies are needed to assess the long-term safety of this diet.

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We would like to acknowledge the rest of the team members in the gastroenterology unit and the nutrition and dietetic department, for their support and assistance with the study.

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Correspondence to Carol Goulding.

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The authors declare that there are no conflicts of interest to disclose.


This study had been performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki and its later amendments.

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Nawawi, K.N.M., Belov, M. & Goulding, C. Low FODMAP diet significantly improves IBS symptoms: an Irish retrospective cohort study. Eur J Nutr 59, 2237–2248 (2020). https://doi.org/10.1007/s00394-019-02074-6

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  • Irritable bowel syndrome
  • Low FODMAP diet
  • Retrospective study
  • Ireland