Efficacy of the low FODMAP diet for treating irritable bowel syndrome: the evidence to date Wathsala S Nanayakkara,1 Paula ML Skidmore,1 Leigh O'Brien,2 Tim J Wilkinson,3 Richard B Gearry,3 1Department of Human Nutrition, University of Otago, Dunedin, New Zealand; 2Dietary Specialists, Christchurch, New Zealand; 3Department of Medicine, University of Otago, Christchurch, New Zealand Abstract: This review summarizes the published clinical studies concerning the management of irritable bowel syndrome (IBS) using restriction of Fermentable Oligosaccharide, Disaccharide, Monosaccharide, and Polyols in the diet (low FODMAP diet). In recent years, the data supporting low FODMAP diet for the management of IBS symptoms have emerged, including several randomized controlled trials, case-control studies, and other observational studies. Unlike most dietary manipulations tried in the past to alleviate gastrointestinal symptoms of IBS, all studies on low FODMAP diet have consistently shown symptomatic benefits in the majority of patients with IBS. However, dietary adherence by the patients and clear dietary intervention led by specialized dietitians appear to be vital for the success of the diet. Up to 86% of patients with IBS find improvement in overall gastrointestinal symptoms as well as individual symptoms such as abdominal pain, bloating, constipation, diarrhea, abdominal distention, and flatulence following the diet. FODMAP restriction reduces the osmotic load and gas production in the distal small bowel and the proximal colon, providing symptomatic relief in patients with IBS. Long-term health effects of a low FODMAP diet are not known; however, stringent FODMAP restriction is not recommended owing to risks of inadequate nutrient intake and potential adverse effects from altered gut microbiota. In conclusion, the evidence to date strongly supports the efficacy of a low FODMAP diet in the treatment of IBS. Further studies are required to understand any potential adverse effects of long-term restriction of FODMAPs. Keywords: irritable bowel syndrome, low FODMAP diet, gastrointestinal symptoms