Inclusion Criteria:

1. 18 - 65 years old
2. IBS-C by Rome III criteria (for IBS-C participants)
3. No abdominal surgery (except appendectomy and cholecystectomy)

Exclusion Criteria:

1. History of Inflammatory Bowel Disease (IBD) , microscopic colitis or celiac disease
2. Use of tobacco products within the past 6 months
3. Use of NSAIDs or aspirin within the past week
4.  Use of oral corticosteroids within the previous 6 weeks
5. Ingestion of artificial sweeteners such as SplendaTM (sucralose), Nutrasweet TM(aspartame), lactulose or mannitol 2 days before the study begins, e.g., foods to be avoided are sugarless gums or mints and diet soda
6. Ingestion of any prescription, over the counter, or herbal medications which can affect gastrointestinal transit 7 days before study begins
   1. Any treatment specifically taken for IBS, including loperamide, cholestyramine, alosetron
   2. Drugs with a known pharmacological activity at 5-HT4, 5-HT2b or 5-HT3 receptors (e.g, tegaserod, ondansetron, tropisetron, granisetron, dolasetron, mirtazapine);
   3. All narcotics (e.g, codeine, morphine, and propoxyphene, either alone or in combination)
   4. Anti-cholinergic agents (e.g, dicyclomine, hyoscyamine, propantheline)
   5. Ultram
   6. GI preparations
      1. Anti-nausea agents (e.g, trimethobenzamide, promethazine, prochlorperazine, dimenhydrinate, hydroxyzine)
      2. Osmotic laxative agents (e.g, lactulose, sorbitol or PEG solutions as Miralax and Glycolax)
      3. Prokinetic agents (e.g, cisapride, metoclopramide, itopride, domperidone)
7. Antimuscarinics
8. Peppermint oil
9. Systemic antibiotics, rifaximin, metronidazole.
10. Bleeding disorders or medications that increase risk of bleeding from mucosal biopsies
11. Score > 8 for anxiety or depression on Hospital anxiety and depression scale.
12. Pregnancy