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Low FODMAP Plus PEG 3350 for the Treatment of Patients With Irritable Bowel Syndrome-Constipation

November 5, 2019


The University of Michigan is testing the effectiveness of PEG 3350 (Miralax) and low FODMAP diet for people with irritable bowel syndrome (IBS) and constipation. The FODMAP  diet is low in simple sugars and short chain carbohydrates carbohydrates, poorly absorbed in the small intestine, and sugar substitutes. The chemical name for these foods is the acronym of FODMAP.


Study Information

The study will compare the PEG 3350, low FODMAP diet against a sham diet that doesn’t include apples, bananas, and pears, wheat, oranges, raspberries, strawberries or rice. Researchers hypothesize the PEG 3350 and low FODMAP diet subjects will have decreased abdominal pain and bloating and increased quality of life with IBS. Those who participate will either follow a low FODMAP diet and take PEG 3350 (Miralax) daily for 4 weeks or follow a sham diet and take PEG 3350 (Miralax) daily for 4 weeks.


Inclusion Criteria

Subjects aged 18 and older meeting the Rome IV criteria for IBS-C*:

Frequent abdominal pain, on average, at least 1 day per week in the last 3 months, associated with two or more of the following:

  1. related to defecation (bowel movement) 
  2. a change in the frequency of stool (reduction of stools)
  3. a change in the form of stool (hard or lumpy stools) AND more than 25% hard stools and less than 25% loose stools 


Exclusion Criteria

  • Any IBS type other than IBS-C (IBS with constipation)
  • More than 3 spontaneous bowel movements during the last 7 days
  • Unable to understand or provide written informed consent
  • Pregnancy
  • Comorbid (possibly deadly) medical problems that may affect gastrointestinal function
  • Inflammatory bowel disease
  • Extra-intestinal disease that affects the gastrointestinal system (i.e., scleroderma, unstable thyroid disease, etc.)
  • Severe renal or hepatic disease
  • Previous abdominal surgery other than appendectomy, cholecystectomy, and gynecologic/urologic surgery
  • Previous treatment with the low FODMAP diet under the supervision of a dietician 
  • Medications not permitted including probiotics, antibiotics, prescription or over-the-counter medication for IBS, and narcotics
  • New antidepressant use (less than 3 months on stable dose)
  • Active participation in another form of dietary therapy



You may participate in this study at the University of Michigan in Ann Arbor, Michigan. If you have any questions feel free to contact Stacy Menees, MD at 734-232-3739 or at You may also contact Elaine Brady, MBA at 734-647-4794 or at



This study is sponsored by the University of Michigan with Stacy, Menees, MD at the Principal Investigator.

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