In study 2, the investigator would like to recruit 30 healthy volunteers, 30 patients with diarrhoea predominantly Irritable Bowel Syndrome, 30 patients with constipation predominantly Irritable Bowel Syndrome and 30 patients with Mixed irritable Bowel Syndrome. The best methods from study 1 for OCTT and WGT will be applied here to assess gastrointestinal transit on these subjects. Based on the first study, the best method to assess OCTT is the Lactose-C13 Ureide breath test and for the WGT, the best method is the MRI marker capsules. Participants will need to fill in questionnaires to assess their stress levels and to fill in symptom questionnaires during the study day.