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Irritable Bowel Syndrome and Control Volunteers: Diet Challenge

Fecal Bile Acids, Fecal Short Chain Fatty Acids and the Intestinal Microbiota in Patients With Irritable Bowel Syndrome (IBS) and Control Volunteers: Diet Challenge

Who can join

Ages 18 to 75 · All sexes · Healthy volunteers welcome

Inclusion Criteria:

* Age 18-75
* Individuals with irritable bowel syndrome (IBS)
* Healthy volunteers (healthy controls) with no prior history of gastrointestinal (GI) disease or symptoms
* No dietary restrictions other than vegetarian

Exclusion Criteria:

* Inflammatory bowel disease, celiac disease, or certain types of abdominal cancer, as well as those with thyroid or liver issues
* Abdominal surgery or abdominal radiation within 6 months of study participation, with an exception for C-section or gallbladder removal
* Use of any prescription, over the counter, or herbal medications known to affect gastrointestinal function or study interpretation, such as opioids, inflammatory drugs or certain antidepressants, within 6 months prior to study participation for healthy volunteers, or within 2 days of study participation for participants with IBS.
* An exception will be permitted for limited use of stable low doses of antidepressants for individuals who have been taking them for a period greater than one month.
* Rescue medication such as Bisacodyl (dulcolax) to relieve severe constipation and allow for stool collection will be permitted when needed.
* Use of Ozempic and Ozempic-type medications
* Pregnant or breastfeeding women
* Antibiotic use within 3 months of study participation
* Use of prebiotics or probiotics within the 2 weeks before the study initiation
* Regular tobacco use within the past 6 months

About the study

The study will investigate the relationship between fecal bile acids, short-chain fatty acids (SCFAs), and the gut microbiota in irritable bowel syndrome (IBS). The central hypothesis of this study is that specific shifts in the GI microbiome composition correlate with altered colonic SCFAs and BAs and contribute to IBS symptoms. Primary aims include: (a) identifying GI microbiome signatures in IBS subtypes (IBS-C and IBS-D) and matched controls, and test if microbiome signatures in these groups correlate with fecal SCFAs and bacterial fermentation of an indigestible carbohydrate (inulin) after a dietary challenge (fecal inulin), and (b) determining if GI microbiome signatures in IBS subtypes and controls correlate with fecal BAs or markers of SCFA production (fecal SCFAs or inulin) and test if BAs correlate with fecal SCFAs or inulin.

The target population is adults ages 18-65 years meeting Rome IV criteria for IBS (both diarrhea- and constipation-predominant, IBS-D and IBS-C) and asymptomatic controls. Primary outcomes will be fecal bile acid excretion and profile, short-chain fatty acid excretion and profile, colonic transit, and fecal microbiota. Secondary outcomes will be stool characteristics based on responses to validated bowel diaries. Stool samples will be collected from participants during the last 2 days of a 4-day 100 g fat diet and split into 3 samples for fecal microbiota, SCFA, and bile acid analysis.

What is being tested

• Inulin (dietary supplement)

Sponsor: University of California, Los Angeles · Participants: 72 · Started: Nov 28, 2024

Contact the study team

Official record on ClinicalTrials.gov — NCT06668922

Locations in the U.S.

Conditions

• Irritable Bowel Syndrome

From ClinicalTrials.gov, data retrieved Oct 1, 2026. Each study sets its own eligibility; the study team decides who can join.