Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) refers to a chronic intestinal disorder marked by recurring symptoms of abdominal pain and alteration of bowel habit. Nutritional influences on this syndrome are due primarily to the effects of macronutrients as well as to idiosyncratic reactions to specific foods.

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Dietary Fat

Fat is the major dietary stimulant of the gastrocolonic response. (1) Patients have an exaggerated and prolonged release of cholecystokinin following ingestion of a fatty meal which appears to cause the onset of their symptoms. (2) Those with diarrhea tend to be more sensitive to a fatty meal than those with constipation. (3)

Sugar

In addition to shortening oro-anal transit time, sugar increases the fecal bile acid concentration, at least partly by increasing bacterial fermentation in the colon. These alterations in colonic activity are known to increase the risk of developing an irritable bowel. (4) Fructose and sorbitol have been shown to cause malabsorption as evaluated by the hydrogen breath test. (5) In one study, patients found to be fructose-intolerant (38% of the IBS group) experienced significant symptom reduction so long as they stuck to a fructose-free diet. (6) While sucrose does not cause malabsorption, it does provoke symptoms--although they are milder. (5) Combined sugar malabsorption patterns are common, and restriction of offending sugars is routinely indicated. (7)

Dietary Fiber