Effect of Diet on Gulf War Illness

Inclusion Criteria: * Gulf War Veterans * Men and women age 25-90 years * Gulf War Illness: Veterans will have Rome III criteria for IBS and two or more of the non-intestinal symptom groups (chronic-once a week or more often-fatigue, insomnia, joint pains, general stiffness, and headache, neurological an mood, respirator and skin symptoms) * Symptoms of \> 6 months duration * No significant findings on physical examination, complete blood count and clinical chemistry panel * Normal gross appearance of the colonic mucosa (small colon polyps not an exclusion criteria) * Veterans with psychological disorders will not be excluded but will be identified for sub-group analysis. Exclusion Criteria: * Current evidence of any lower gastrointestinal disorder such as celiac disease or inflammatory bowel disease * Clinically significant chronic disease: HIV, cardiac, pulmonary, hepatic or renal dysfunction * Presence of Giardia antigen, and Clostridium difficile toxin in stool * Current history of drug or alcohol abuse * Investigator perception of patient's inability to comply with study protocol * Recent change in gastrointestinal medications * Subject is currently participating in another research protocol. These subjects will be allowed to enroll after a washout period of one month.