Inclusion Criteria:

• Men and women must be: 18-70 years old, have had symptoms of Irritable Bowel Syndrome (IBS) at least 6 mo prior to their diagnosis, and have had their diagnosis for at least 6 months, and the diagnosis had to be made by a health care provider (e.g., internist, gastroenterologist, family, nurse practitioner, physician assistant).
• In addition, the subjects must be experiencing IBS symptoms as described in the Rome-III criteria.161 That is recurrent abdominal pain or discomfort at least 3 days a mo in the last 3 mo associated with 2 or more of the following: improvement with defecation, onset associated with a change in frequency or form (appearance) of their stool.
• Adults 50 or older must have a negative colonoscopy, sigmoidoscopy, abdominal ultrasonography, or barium enema.
• Anyone with a "red flag" symptom (e.g., lost 10 lbs without trying, blood in stool, anemia) will be contacted for additional clarification.

Exclusion Criteria:

• Participants will be excluded if they are taking the following medications: antibiotics, daily use of anticholinergics, tricyclic antidepressants, calcium-channel blockers
• Have a medical history of abdominal surgery (except appendectomy, Caesarian section, tubal ligation, laparoscopic cholecystectomy, hysterectomy, or abdominal wall hernia repair)
• Active organic GI disease, gluten intolerance (celiac disease), or chronic moderate to severe pain condition (e.g., low back pain, fibromyalgia)
• Recent travel to regions with endemic parasitic diseases
• Current mental health disorders (psychosis, bipolar disorder, current moderate to severe depressive episode, suicide attempt, drug or alcohol abuse or dependence within 2yrs)
• Cardiac valvular disease, immune compromised immunologic disorders (e.g., autoimmune conditions)
• Women who are pregnant, breast feeding, or planning to get pregnant in the next year