Irritable Bowel Syndrome and Control Volunteers: Diet Challenge

During the study:

Screening/Visit 1

• Participants will be asked to read and sign this informed consent after all questions about the study have been answered to satisfaction.
• This is a screening visit, and we may determine that a participant is ineligible to continue to participate in the study.
• The study team will collect medication and medical history.
• A physical exam will be performed by the physician. Vital signs and body measurements will be collected.
• Participants will be provided with a take-home lasagna meal (vegetarian and non-vegetarian option) and dessert.
• Participants will receive a stool collection kit and instructions for the collection, storage, and transportation of stool.
• Instructions will be provided for a low fiber, high fat diet for Days 2-4.
• Participants will be asked to complete diet recall using the ASA24 and a bowel pattern diary to record bowel symptoms over the course of the study.
• IBS participants will complete the irritable bowel syndrome severity scoring system questionnaires (IBS-SSS).

Day 2-4 (at home):

• Participants will record stool symptoms and patterns in a diary daily.
• Participants will be instructed to consume a low fiber diet (maximum one piece of fruit and 100 g of vegetables a day, and white flour instead of whole grain products), avoid alcohol, and start a 4-day 100 g fat diet.
• On the evening before Day 5, participants will be instructed to collect a stool sample at home and return during Visit 2.

Day 5 (Visit 2):

• Participants will return to the clinic on Day 5 after an overnight fast.
• Participants in the reproductive age range will be given a urine pregnancy test prior to inulin ingestion and the study team will confirm a negative test result.
• Participants will receive breakfast onsite. The non-vegetarian option will consist of pancakes, butter, syrup, hard-boiled eggs, and bacon. The vegetarian option will substitute the bacon with a cheese snack (approximately 790 to 840 kcal) along with 10 g inulin Orafti® powder) thoroughly mixed in 200 mL of water.
• Take-home meals will be provided for lunch and dinner and are to be consumed at 4 and 8 hours from breakfast.
• IBS participants will complete the irritable bowel syndrome severity scoring system (IBS-SSS) questionnaire.
• A stool sample will be collected on Day 5.
• Participants will continue to complete diet recall using the ASA24 and a bowel pattern diary to record bowel symptoms over the course of the study.

Day 6

• Participants will be instructed to collected a final stool sample (Day 6).
• Participants will continue to complete diet recall using the ASA24 and a bowel pattern diary to record bowel symptoms over the course of the study.

Day 7 (Visit 3)

• Participants will return to the clinic to return stool collections (Day 5 and Day 6), the daily diaries, and the IBS-SSS forms (if applicable).

Day 30-90 (Optional dietary follow-up): To further assess the utility of the 24 hour dietary recall, willing participants will be invited to participate in a an optional follow-up activity during which they will complete the Automated Self-Administered Dietary Assessment Tool with or without assistance of a trained interviewer. Interested volunteers will be contacted by phone and provided instructions on how to complete the tool online by the study team.

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