- Female and male patients with IBS between the ages of 18 and 68 will be recruited. IBS will be diagnosed according to the Rome III diagnostic criteria (Drossman and Dumitrascu, 2006). The history of previous chronic GI symptoms suggestive of IBS should be at least 3 months (not necessarily consecutive) over the preceding 6 months. The stool culture of each subject should be negative for hemoccult, pathogens (Salmonella and Shigella), parasites (Giardia) and ova/ cyst. Only patients who had IBS symptoms for at least one month prior to the study and whose IBS symptom score is of at least a moderate severity on at least one of IBS symptoms will be eligible for inclusion into the study.