Irritable bowel syndrome (IBS) is a very common, sometimes disabling disorder for which there is a lack of effective treatments. Many patients report that the make-up of the diet has an effect on their symptoms. The western diet consists of many different molecules. Some of them are small, fermentable and cannot be absorbed (FODMAPs). The low FODMAP diet was recently developed in Australia. In randomised controlled trials 37-45% of IBS patients experience symptom reduction with this diet. The low FODMAP diet starts with a 6-week elimination phase. If symptoms decrease substantially, it is followed by a structured reintroduction phase of the various FODMAPs over several weeks, after which patients are left with a diet that is simpler to follow.