Nutritional Influences on Illness: Irritable Bowel Syndrome

Nutritional Influences on Illness: Irritable Bowel Syndrome

The irritable bowel syndrome refers to a chronic intestinal disorder marked by recurring symptoms of abdominal pain and alteration of bowel habits. Its cause is considered to be unknown.

Nutritional influences on this syndrome are due primarily to the effects of macronutrients as well as to idiosyncratic reactions to specific foods. Fat is the major dietary stimulant of the gastrocolonic response, and patients react excessively to a fatty meal (especially those with diarrhea) with provocation of symptoms.( 1)

Refined sugar may also contribute to the syndrome. In addition to shortening oro-anal transit time, it 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.( 2) Fructose and sorbitol, but not sucrose, have been shown to cause malabsorption as evaluated by the hydrogen breath test; sucrose does not cause malabsorption and, while it does provoke symptoms, the symptoms are milder.( 3)

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While dietary fiber such as wheat bran increases stool weight, double-blind crossover studies have failed to confirm the results of open trials suggesting that the addition of wheat bran( 4, 5) or corn fiber( 6) may be helpful. One study even found wheat bran to be less effective than placebo in regard to abdominal pain and the urgency to defecate.( 4) By contrast, patients report better results with fiber products that are not normally in the diet. An example is psyllium( 7) which has been shown to be better than placebo in reducing constipation and decreasing elevated intestinal transit times.( 8)

The failure of well-controlled studies to find benefit from wheat and corn bran may well be due to sensitivities to these substances, which could cancel out any benefits from their physiological effects. Indeed, considerable evidence has accumulated that food sensitivities are a major cause of irritable bowel syndrome, and common foods such as grains are some of the most frequent offenders.( 9) The data suggest that simply eliminating common foods from the diet for two weeks is likely to result in symptom relief for perhaps as many as two-thirds of your patients.( 10)

Briefly, then, the nutritional prescription for irritable bowel syndrome is as follows: Avoid fatty meals and minimize the intake of refined sugars. Try adding one teaspoon of psyllium twice daily for at least a few days if dietary changes are ineffective. Finally, if psyllium also fails to be helpful, eliminate common foods from the diet for a two-week trial. If symptoms subside, add foods back slowly to identify the offenders.

Even though this treatment protocol is quite simple, it should provide your patients with at least some relief most of the time!

Doctor Werbach cautions that the nutritional treatment of illness should be supervised by physicians or practitioners whose training prepares them to recognize serious illness and to integrate nutritional interventions safely into the treatment plan.

(1.) Kellow JF et al. Dysmotility of the small intestine in irritable bowel syndrome. Gut 29(9):1236-43, 1988

(2.) Kruis Wet al. Influence of diets high and low in refined sugar on stool qualities, gastrointestinal transit time and fecal bile acid excretion. Gastroenterology 92:1483, 1987

(3.) Rumessen JJ, Gudmand-Hyer E. Functional bowel disease: Malabsorption and abdominal distress after ingestion of fructose, sorbitol, and fructose sorbitol mixtures. Gastroenterology 95(3):694-700, 1988)

(4.) Cann PA, Read NW, Holdsworth CD. What is the benefit of coarse wheat bran in patients with irritable bowel syndrome? Gut 25: 168-73, 1984

(5.) Lucei MR et al. Is bran efficacious in irritable bowel syndrome? A double blind placebo controlled crossover study. Gut 28:221, 1987

(6.) Cook IJ et al. Effect of dietary fiber on symptoms and rectosigmoid motility in patients with irritable bowel syndrome. A controlled, crossover study. Gastroenterology 98(1):66-72, 1990

(7.) Francis CY, Whorwell PJ. Bran and irritable bowel syndrome: time for reappraisal. Lancet 344:39-40, 1994

(8.) Prior A, whorwell PJ. Double blind study of ispaglula in irritable bowel syndrome. Gut 28(11):1510-13, 1987

(9.) Nanda R et al. Food intolerance and the irritable bowel syndrome. Gut 30(8):1099-104, 1989

(10.) Alun-Jones VA et al. Food intolerance: A major factor in the pathogenesis of irritable bowel syndrome. Lancet ii: 1115-7, 1982

Townsend Letter for Doctors & Patients.


By Melvyn R. Werbach

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