An interventional study of Low FODMAP diet/PEG 3350 and sham diet/PEG 3350 in Irritable Bowel Syndrome Characterized by Constipation, sponsored by University of Michigan. Recruiting at 1 site in United States. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2025-03-04.
Sponsored by University of Michigan · Not applicable, Interventional, and Treatment
Consecutive patients with Irritable Bowel Syndrome with Constipation (IBS-C) will be recruited from the outpatient clinics of the University of Michigan Health System. Eligible patients will be asked to participate in a study that will test the efficacy the PEG 3350 + a diet low in fermentable oligo, di, monosaccharides, and polyols (FODMAP) vs. PEG 3350 plus sham diet. Blinding dietary advice trials is challenging and therefore the sham diet was based on the criteria set forth by Staudacher et al. which emphasizes that the diet must give the impression that is the true intervention diet with similar restrictions, modifications, and time intensity without impacting the intake of essential nutrients, fiber, and FODMAPs. An example of the sham diet's carbohydrates includes: apples, bananas, and pears, and wheat. Oranges, raspberries, strawberries and rice would not be allowed. Additionally, the physicians analyzing the data will be blinded as to which group the patients were randomized.
A. Specific Aims: While a diet low in fermentable oligo, di, monosaccharides and polyols (FODMAPs) has gained popularity as a treatment for patients with Irritable Bowel Syndrome and diarrhea (IBS-D), the impact of this diet on patients with IBS and constipation (IBS-C) is unknown. We propose a randomized, controlled trial in IBS-C patients to compare the efficacy of PEG 3350 and the low FODMAP diet to PEG 3350 and a sham diet. We hypothesize that:
We plan to test our central hypothesis and, thereby, accomplish the objective of this application by pursuing the following 2 specific aims:
Aim 1: Compare the proportion of patients with IBS-C on a diet of low FODMAP diet plus PEG 3350 vs. sham diet plus PEG 3350 reporting an improvement of abdominal pain. Our working hypothesis is that a higher proportion of patients randomized to the low FODMAP diet plus PEG 3350 will experience a reduction in the abdominal pain when compared to PEG 3350 plus sham diet alone.
Aim 2: Compare the efficacy of the low FODMAP diet plus PEG 3350 vs. sham diet plus PEG 3350 on pre-specified key clinical and disease specific quality of life endpoints in patients with IBS-C. Through our randomized controlled trial, we will assess the impact of the dietary interventions on stool consistency, stool frequency, and bloating and quality of life endpoints.
A positive result to this study would have significant impact on the treatment of patients with IBS by expanding the indications for the low FODMAP diet to all affected patients, regardless of bowel subtype. This would be particularly relevant to IBS-C patients for whom we currently have few evidence-based diet recommendations outside of increasing fiber intake.
1,062 studies on the registry are indexed under Irritable Bowel Syndrome; 190 are open to participants now.
This study's planned enrollment of 78 is close to the median of 71 across 853 interventional studies indexed under Irritable Bowel Syndrome.
Browse Irritable Bowel Syndrome studies →University of Michigan is the lead sponsor of 1,475 studies on the registry; 196 are open to participants now.
Of its 162 completed or terminated interventional studies of FDA-regulated products, 128 (79%) have results posted.
Counted across the registry records on this site, refreshed daily.
Exclusion Criteria:
Subjects will follow a low FODMAP diet and will take PEG 3350 (Miralax).
Other: Low FODMAP diet/PEG 3350
Subjects will follow a sham diet and will take PEG 3350 (Miralax).
Other: sham diet/PEG 3350
Subjects will follow a low FODMAP diet and will take PEG 3350 (Miralax) at 17.7 g (single dose) daily for 4 weeks.
Also known as: low FODMAP diet
Subjects will follow a sham diet and will take PEG 3350 (Miralax) at 17.7 g (single dose) daily for 4 weeks.
Also known as: sham diet
Improvement of abdominal pain as measured by 11-point numerical rating scale
Compare the proportion of patients with IBS-C on a diet of low FODMAP diet plus PEG 3350 vs. sham diet plus PEG 3350 reporting an improvement of abdominal pain. It is defined 30% reduction in abdominal pain during weeks 3 \& 4 of each diet compared with baseline using an 11-point numerical rating scale (NRS) (0-no pain, 11-intolerable pain). Appropriate between-group statistical comparisons will be conducted.
Time frame: during weeks 3 and 4
Bloating
The change in mean score from baseline on the daily 11-point NRS averaged over each treatment week for bloating severity will be compared between the 2 groups.
Time frame: each treatment week (4 weeks)
abdominal discomfort
30% reduction in abdominal discomfort during weeks 3 \& 4 of each diet compared with baseline using an 11-point NRS. Appropriate between-group statistical comparisons will be conducted.
Time frame: during weeks 3 and 4
Mean number of SBMs per day
These will be measured in the last treatment week (the 7-day period before visit 4): The proportion of responders between the 2 groups will be compared. An SBM was defined as a bowel movement that occurred without the use of rescue medication or ≥24 h after the use of rescue medication.
Time frame: week 4
Mean weekly number of spontaneous complete bowel movements
These will be tallied in the last treatment week (the 7-day period before visit 4):(SCBMs; derived from the number of SBMs without a feeling of incomplete evacuation)
Time frame: last treatment week
Composite endpoint: Full responder was defined as a patient with >3 SBM per week, an increase of ≥1 SBM per week and >30% pain reduction.
during weeks 3 \& 4
Time frame: during weeks 3 & 4
stool consistency
a responder will be defined as one who reports an increase in mean daily BSFS value of 1 or more compared to baseline for ≥2 of 4 treatment weeks. The proportion of responders between the 2 groups will be compared. Between group differences in the proportion of patients with an increase in BSFS value of ≥1
Time frame: Over the 4 weeks of treatment
Straining
The change from baseline in daily numerical rating scale scored as 0 (none), 1 (slight), 2 (mild), 3 (moderate) and 4 (severe) scores averaged over each treatment week for straining will be compared between the 2 groups
Time frame: 4 weeks
IBS-QOL
assess change in IBS-QOL from baseline and the last week of treatment week 4
Time frame: baseline and week 4
HADS score
assess change in HADS score from baseline and the last week of treatment of week 4
Time frame: baseline and week 4
WPAI questionnaire
assess change in WPAI questionnaire from baseline and the last week of treatment of week 4
Time frame: baseline and week 4
Sleep Assessment questionnaire
assess change in Sleep Assessment questionnaire from baseline and the last week of treatment of week 4
Time frame: baseline and week 4
Eligibility is decided by the study team. Share this record with your doctor or contact the team directly.
Contact study teamGet an email when the registry record changes — status, dates, results — or when someone posts here.
Sign in to followQuestions and observations about this study, from anyone following it. Not medical advice, and not a channel to the study team — their contact details are on the registry record.
Sign in to join the discussion. Reading takes no account; posting does. You choose a display name, and a pseudonym is the default.
Nothing here yet. If you are running this trial, taking part in it, or weighing whether to, this is the place to say so.
University of Michigan