The purpose of this study is to find out the relationship between the bile acids, fatty acids (fatty acids are part of the diet) and bacteria that are present in the intestines.

There is emerging evidence that alterations in bile acids and SCFA associated with IBS could be associated with changes in the gut microbiota. In addition to modulating levels of intraluminal organic acids, it has been hypothesized that gut microbiota may alter local immune responses, modulate visceral pain responses, and impair gut barrier function.

Our overall goal is to investigate the relationship between fecal bile acids, SCFA and the gut microbiota in IBS. Results of this pilot study could reveal insights into the interplay of the gut microbiota and small molecule mediators of IBS to suggest targeted clinical strategies for improved diagnosis and management of this important syndrome.

AIM 1: Test the hypothesis that fecal organic acids (SFCA and bile acids) and fecal microbiota play an important role in IBS.

AIM 2: Test the hypothesis that there is association between colonic transit and fecal microbiota in IBS

Inclusion Criteria:

• Patients with IBS, ages 18-65 fulfilling Rome IV criteria and asymptomatic controls with no prior history of GI disease or symptoms.
• Participants should be on a stable and consistent diet regimen and should not be following an extreme diet intervention such as gluten-free or a low FODMAP diet at the time of study participation.

Exclusion Criteria:

• Participants with microscopic/lymphocytic/collagenous colitis, inflammatory bowel disease, celiac disease, visceral cancer, chronic infectious disease, immunodeficiency, uncontrolled thyroid disease, history of liver disease or history of elevated AST/ALT > 2.0x the upper limit of normal
• Prior radiation therapy of the abdomen or abdominal surgeries with the exception of appendectomy or cholecystectomy > 6 months prior to study initiation
• Ingestion of any prescription, over the counter, or herbal medications which can affect GI transit or study interpretation (e.g. opioids, narcotics, anticholinergics, norepinephrine reuptake inhibitors, nonsteroidal anti-inflammatory drugs, COX-2 inhibitors, bile acid sequestrants) within 6 months of study initiation for asymptomatic volunteers or within 2 days before study initiation for IBS patients
• Any females who are pregnant or trying to become pregnant or breast-feeding
• Antibiotic usage within 3 months prior to study participation
• Prebiotic or probiotic usage within the 2 weeks prior to study initiation
• Use of tobacco products within the past 6 months.

The target study population will be patients with IBS (both diarrhea- and constipation-predominant) and healthy controls.