Irritable Bowel Syndrome: What Kind of Fiber, What Kind of Oils?

Desiree Lie, MD, MSEd

Posted: 02/12/2009

Case 1

Mr. X is a healthy, active 33-year-old man who travels frequently for his job as a sales representative. He has a history of 1 depressive episode, which occurred at age 24 when he was attending graduate school. He was treated over a 6-month period with a selective serotonin reuptake inhibitor (SSRI), and he has not had a recurrence since. In his late 20s, he was diagnosed with constipation-predominant irritable bowel syndrome (IBS). Until recently, he was able to control his symptoms by carefully managing his diet, which he did by maintaining a high fiber intake and by avoiding foods that trigger his symptoms. His workup at the time of diagnosis by a gastroenterologist included colonoscopy and other laboratory tests to exclude other bowel pathology.

Over the past year, the IBS has increased in severity, resulting in cyclical constipation and associated abdominal spasms every 3 to 6 weeks. The IBS has begun to interfere with his work productivity, because he must take time off every few months. He has tried lactulose as a laxative, and he has increased his bran fiber intake, but there has been no improvement.

He is seeking control of his symptoms, but he prefers to try dietary measures before resorting to medications. He has no symptoms of depression and no recent major life stressors, other than a heavy workload. There are no bowel symptoms suggestive of peptic ulcer disease. Similarly, there are no “red flags” or systemic symptoms, such as weight loss, that would suggest the presence of other chronic diseases.

The physical examination reveals a healthy, young man with a body mass index of 26. The cardiovascular and respiratory examinations are normal. The abdominal examination, on deep palpation, reveals slight tenderness over the large bowel, mild distension, and an absence of masses. The rectal examination is normal, and test results for occult fecal blood are negative. The mental status examination is normal, and the constipation and associated abdominal spasms within normal limits.

What are some options for improving his symptoms?

Case 2
Mrs. Y is a 44-year-old woman with diarrhea-predominant IBS that was diagnosed a year ago after she underwent a complete gastroenterologic workup to exclude other pathologies. Her symptoms are persistent, and this causes her inconvenience at work, limits her social activities, and affects her ability to perform daily functions. Because of her IBS, she leads a sedentary lifestyle.

She has tried an anxiolytic for the abdominal pain and loperamide for the diarrhea, but the abdominal distension, bloating, and painful spasms continue. She takes fiber in various forms, including Metamucil® and wheat bran, but the fiber supplements do not seem to control the diarrhea. She admits that life is stressful and has been in counseling for a few months.

What else can she try to better control her IBS symptoms?