Gulf War Digestive Health Study

Inclusion Criteria: * Men and women age 32-75 years * Rome III criteria for diarrhea-predominant IBS * Symptom onset after an apparent episode of acute gastroenteritis * Symptoms of \> 3 months duration * Normal endoscopic appearance of the colonic mucosa * Negative markers for celiac disease and inflammatory bowel disease. * Normal thyroid function and serum calcium levels. * Must have served in the military or reserves during the time of Operation Desert Storm (August 1990 to May 1991) Exclusion Criteria: * Clinically significant cardiac, pulmonary, hepatic or renal dysfunction * History of/or presence of systemic malignancy * Current evidence of any gastrointestinal disorder such as celiac disease or inflammatory bowel disease (i.e. Crohns disease or ulcerative colitis) * Current effects of drug or alcohol abuse * Investigator perception of patients inability to comply with study protocol * Unstable psychiatric disease * Recent change in gastrointestinal medications * Subjects with a positive pregnancy test * Subject is currently participating in another research protocol that could interfere or influence the outcome measures of the present study