Serine Proteases in Gastrointestinal Function and Irritable Bowel Syndrome (IBS)

Inclusion Criteria: * Any sex, race, or ethnicity. * At least 18 years of age (no upper age limit). * D-IBS patients must meet Rome III criteria for IBS and must have been evaluated by a physician to exclude other diseases that could explain the symptoms. For the latter, patients self statement is acceptable (no official document is required). * Participation in Dr. Whitehead's 'heterogeneity of IBS' and/or Dr. Ringel's 'intestinal inflammation in patients with D-IBS' research study. Exclusion Criteria: * Healthy controls must have no significant or recurring gastrointestinal symptoms. * Patients and healthy controls should not have a serious, unstable medical condition. * Patients and healthy controls must have had no gastrointestinal tract surgery other than appendectomy or cholecystectomy. * Patients and healthy controls must not be pregnant (by self-report). Pregnant women will not be allowed to participate as pregnancy can affect gastrointestinal symptoms. * Patients and healthy controls must not have a history of inflammatory bowel disease, celiac disease, or other diagnosis that could explain chronic or recurring bowel symptoms in IBS patients or controls. * Patients and healthy controls should have no history of lactose malabsorption (by self-report). * Patients and healthy controls should have no history of clinical symptoms of acute infections during the last 8 weeks prior to enrolment in the study. * Patients and healthy controls should have no history of anti-inflammatory agents including aspirin, non-aspirin, non-steroid anti-inflammatory (NSAID) or steroids in the last four weeks prior to study enrollment. * Patients should not intentionally consume probiotics or undergo antibiotic treatment during the last 4 weeks prior to enrolment in the study. If the subject consumed any of these medications, a washout period of 4 weeks will be required). * Patients must have no history of fainting or light headedness during periods of fasting. * Patients must not have diabetes mellitus, or any similar conditions, that would cause an adverse reaction to the sugar drink.