1 3 Eur J Nutr DOI 10.1007/s00394-015-0922-1 ORIGINAL CONTRIBUTION Does a diet low in FODMAPs reduce symptoms associated with functional gastrointestinal disorders? A comprehensive systematic review and meta-analysis Abigail Marsh 1 · Enid M. Eslick 1 · Guy D. Eslick 1 Received: 23 March 2015 / Accepted: 4 May 2015 © Springer-Verlag Berlin Heidelberg 2015 In addition, there was a significant improvement in the IBS-QOL score for RCTs (OR 1.84, 95 % CI 1.12–3.03; I 2 = 0.00, p = 0.39) and for non-randomized interventions (OR 3.18, 95 % CI 1.60–6.31; I 2 = 0.00, p = 0.89). Fur- ther, following a low FODMAP diet was found to signifi- cantly reduce symptom severity for abdominal pain (OR 1.81, 95 % CI 1.13–2.88; I 2 = 0.00, p = 0.56), bloating (OR 1.75, 95 % CI 1.07–2.87; I 2 = 0.00, p = 0.45) and overall symptoms (OR 1.81, 95 % CI 1.11–2.95; I 2 = 0.00, p = 0.4) in the RCTs. In the non-randomized interventions similar findings were observed. Conclusion The present meta-analysis supports the effi- cacy of a low FODMAP diet in the treatment of functional gastrointestinal symptoms. Further research should ensure studies include dietary adherence, and more studies looking at greater number of patients and long-term adherence to a low FODMAP diet need to be conducted. Keywords FODMAP · Diet · Functional gastrointestinal disorders · FGID · Symptoms · Meta-analysis Introduction Functional gastrointestinal symptoms such as abdominal pain, bloating (distension), constipation, diarrhea and flatu- lence (gas) have been noted in patients with irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD). IBS is the most common diagnosis made by gastroenterolo- gists [1] and affects between 7 and 15 % of the population [2, 3]. The condition is characterized by recurrent episodes of functional gastrointestinal symptoms when anatomi- cal abnormalities and inflammation have been excluded. The pathophysiological mechanisms underlying IBS are not clearly understood [4] and are thought to result from a Abstract Background Functional gastrointestinal symptoms such as abdominal pain, bloating, distension, constipation, diar- rhea and flatulence have been noted in patients with irrita- ble bowel syndrome (IBS) or inflammatory bowel disease (IBD). The diversity of symptoms has meant that finding an effective treatment has been challenging with most treat- ments alleviating only the primary symptom. A novel treat- ment option for IBS and IBD currently generating much excitement is the low fermentable, oligo-, di-, mono-sac- charides and polyol (FODMAP) diet. The aim of this meta- analysis was to determine the evidence of the efficacy of such a diet in the treatment of functional gastrointestinal symptoms. Methods Electronic databases were searched through to March 2015 to identify relevant studies. Pooled odds ratios (ORs) and 95 % confidence intervals were calculated for the effect of a low FODMAP diet on the reduction in IBS [Symptoms Severity Score (SSS)] score and increase in IBS quality of life (QOL) score for both randomized clini- cal trials (RCTs) and non-randomized interventions using a random-effects model. Results Six RCTs and 16 non-randomized interven- tions were included in the analysis. There was a significant decrease in IBS SSS scores for those individuals on a low FODMAP diet in both the RCTs (OR 0.44, 95 % CI 0.25– 0.76; I 2 = 35.52, p = 0.00) and non-randomized interven- tions (OR 0.03, 95 % CI 0.01–0.2; I 2 = 69.1, p = 0.02). * Guy D. Eslick eslickg@med.usyd.edu.au 1 The Whiteley-Martin Research Centre, Discipline of Surgery, The University of Sydney, Nepean Hospital, Level 3, Clinical Building, Penrith, NSW 2751, Australia