The investigators will give four different drinks: one beverage consisting of a very well absorbed sugar, glucose, another consisting of the less well absorbed sugar fructose, a third which is a mixture of glucose and fructose, and a fourth consisting of several fructose subunits joined together (called fructan). The investigators will take MRI images of the stomach and intestines at intervals for 5 hours and compare these with the feelings of distension and bloating in our volunteers. The results will act as control for subsequent studies in IBS patients and these may help design diets to reduce symptoms in IBS.