The Role of FODMAPs in Upper GI Effects, Colonic Motor Activity and Gut-brain Signaling at the Behavioral Level

In this study, the investigators aim to assess the effect of acute FODMAP infusion on gastric motility and on gastrointestinal and psychological symptoms. 20 healthy volunteers and 20 patients with irritable bowel syndrome (IBS) will undergo respectively four and two/three pressure measurements of the stomach after an overnight fast as a measure for gastric motility. During this pressure measurement, which takes approximately 4 hours, one of four FODMAP or control solutions will be administered directly into the stomach through a nasogastric tube. Administration will be stopped when the participant is fully satiated. The four solutions that will be tested in healthy volunteers are (1) a fructan solution, (2) a fructose solution, (3) a FODMAP mix and (4) a glucose solution as a control. In IBS patients, only the fructan and glucose solution will be tested, where after they can choose to come for a third visit to test the fructose solution. The solutions will be tested on separate occasions in a randomized order. During the pressure measurement, participants will be asked to complete several questionnaires: (1) a gastrointestinal symptom questionnaire to assess their gastrointestinal symptoms, (2) a satiation questionnaire during infusion of one of the solutions, (3) psychological questionnaires (POMS, SAM, PANAS and STAI) to evaluate possible psychological effects of FODMAP infusion. The investigators hypothesize that there will be differences in gastric motility between healthy volunteers and IBS patients. Furthermore, it is hypothesized that gastrointestinal symptoms will be increased in IBS patients, and that FODMAP infusion will have more psychological effects in patients than in healthy volunteers.