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Irritable Bowel Syndrome (IBS), Diet & Fiber

Posted Aug 30 2009 12:31pm




Health Report:


Irritable Bowel Syndrome (IBS), Diet & Fiber


"A critical weekly review of important new research findings for health-conscious readers..."


By, Robert A. Wascher, MD, FACS
Photo of Dr. Wascher

Updated:  08/30/2009

The information in this column is intended for informational purposes only, and does not constitute medical advice or recommendations by the author.  Please consult with your physician before making any lifestyle or medication changes, or if you have any other concerns regarding your health.






An estimated 10 to 20 percent of the population suffers from a complex of gastrointestinal symptoms that are collectively referred to as irritable bowel syndrome (IBS). Irritable bowel syndrome affects women three times more commonly than men, and has historically been considered a “wastebasket” diagnosis for patients with functional gastrointestinal (GI) complaints when no other specific diagnosis can be found. While the precise mechanisms underlying IBS are not well understood at this time, various theories have been proposed. These include abnormal responses to infections of the GI tract, abnormal hormonal and neurologic function of the intestines, hypersensitivity to certain types of foods, abnormal motility of the colon, a “hyper-awareness” of bodily functions, and certain psychiatric conditions, in addition to other hypotheses. (It is almost certain, however, that there is more than one cause for IBS.)
There are a variety of symptoms that have been associated with IBS, and the incidence, severity and frequency of each of these symptoms varies considerably from one IBS patient to another. Typically, however, IBS-associated symptoms include bloating, crampy abdominal pain, diarrhea alternating with periods of constipation, and the passage of clear or white mucus from the rectum. In many cases, IBS symptoms are more pronounced after eating, and patients with IBS often experience a powerful urge to move their bowels after meals. IBS symptoms are also more frequent and more severe during times of stress. In women with IBS, these distressing symptoms may become more intense around the time of patients’ menstrual periods. Other symptoms that have been commonly observed in patients with IBS include frequent heartburn, nausea and vomiting.
Because the true causes of IBS are poorly understood, there have been a wide range of treatments recommended for this syndrome. For example, exercise and other stress-reducing activities may be helpful for some IBS sufferers. Giving up tobacco, and reducing or eliminating alcohol consumption may also help to reduce IBS symptoms, while promoting improved overall health at the same time. Keeping a food diary can also help to identify foods that tend to provoke or worsen IBS symptoms in many patients. Finally, dietary fiber supplementation has been almost universally advocated by most IBS experts. Unfortunately, these and other recommended treatments for IBS are often ineffective in reducing the troubling GI symptoms of irritable bowel syndrome for many patients. Moreover, there have been only a handful of small, prospective, randomized clinical research studies, to date, looking at dietary interventions for IBS. Now, a newly published prospective, randomized, placebo-controlled fiber supplement study offers some helpful new clinical data regarding the treatment of IBS, and this data offers some hope for IBS sufferers. 
This new clinical study, just published in the British Medical Journal, enrolled 275 adult patients with IBS. Patients were then randomized to one of three different groups within this study. A control group was given rice flour, which is a starch and contains no significant fiber. A second group of patients were given supplements of indigestible (insoluble) fiber in the form of bran. The third group received digestible (soluble) supplementation with psyllium powder (Metamucil). The type of supplement received by each patient wasn’t revealed until the end of the study.
Following 12 weeks of fiber (or placebo) treatment, the participants in this study were reassessed for the severity of their symptoms. Among the three treatment groups in this IBS fiber supplementation study, only supplementation with psyllium significantly improved IBS-related symptoms. When compared to the placebo group, IBS patients who had been randomized to receive psyllium were 22 percent more likely to report improved IBS symptoms. In comparison, there was no statistically significant improvement in IBS symptoms with bran fiber supplementation when compared to placebo, and, in fact, many IBS patients in this group actually dropped out of this clinical study because their IBS symptoms worsened while taking bran fiber supplements.
It should be noted there were two significant limitations of this study. First of all, nearly 40 percent of the patients who volunteered for this trial dropped out prematurely. However, this is a rather common phenomenon in clinical studies where the treatments are unpleasant, or when the response to such treatments is not immediate or dramatic. A second limitation is that, despite the researchers’ efforts to “blind” the patients as to which supplement they were actually receiving, three-fourths of the patients were still able to accurately guess the supplement that they had been randomized to receive. This finding, of course, introduces the possibility of bias in the perceptions and responses of these patients at the conclusion of the study.  Moreover, to complicate matters further, and as prior studies have also shown, 35 percent of the control group of patients also reported an improvement in their IBS symptoms with a placebo supplement.
While there are significant limitations inherent in this study, it still represents one of only a very few existing prospective, randomized, placebo-controlled clinical research studies of fiber supplementation as a treatment for IBS. Based upon the findings of this study, despite its limitations, dietary supplementation with soluble (digestible) fiber appears to be a prudent and potentially helpful intervention for patients suffering from IBS-related symptoms; while insoluble (indigestible) fiber supplements, like bran, may actually worsen the symptoms of IBS.

Disclaimer:  As always, my advice to readers is to seek the advice of your physicianbeforemaking any significant changes in medications, diet, or level of physical activity


Dr. Wascher is an oncologic surgeon, a professor of surgery, a widely published author, and a Surgical Oncologist at the Kaiser Permanente healthcare system in Orange County, California

(Anticipated Publication Date:  March 2010)

Link to TV36 Interview with Dr. Wascher

(Click above image for TV36 interview of Dr. Wascher)


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