Elsevier

The Lancet

Volume 352, Issue 9135, 10 October 1998, Pages 1187-1189
The Lancet

Early Report
Abnormal colonic fermentation in irritable bowel syndrome

https://doi.org/10.1016/S0140-6736(98)02146-1Get rights and content

Summary

Background

The cause of irritable bowel syndrome (IBS) is unknown. It may follow gastroenteritis and be associated with an abnormal gut flora and with food intolerance. Our study was designed to assess whether these factors were associated with colonic malfermentation.

Methods

We carried out a crossover controlled trial of a standard diet and an exclusion diet matched for macronutrients in six female IBS patients and six female controls. During the final 72 h on each diet, faecal excretion of fat, nitrogen, starch, and non-starch polysaccharide NSP was measured, and total excretion of hydrogen and methane collected over 24 h in a purpose-built 1·4 m3 whole-body calorimeter. Breath hydrogen and methane excretion were then measured for 3 h after 20 g oral lactulose.

Findings

The maximum rate of gas excretion was significantly greater in patients than in controls (2·4 mL/min IQR 1·7–2·6 vs 0·6, 0·4–1·1). Although total gas production in patients was not greater than in controls (median 527 mL/24 h IQR 387–660 vs 412, 234–507), hydrogen production was higher (332, 318–478 vs 162, 126–217, p=0·009). In patients, the exclusion diet reduced symptoms and produced a fall in maximum gas excretion (0·5 mL/min IQR 0·3–0·7). After lactulose, breath hydrogen was greater on the standard than on the exclusion diet.

Interpretation

Colonic-gas production, particularly of hydrogen, is greater in patients with IBS than in controls, and both symptoms and gas production are reduced by an exclusion diet. This reduction may be associated with alterations in the activity of hydrogen-consuming bacteria. Fermentation may be an important factor in the pathogenesis of IBS.

Introduction

Irritable bowel syndrome (IBS) is common, but of unknown cause.1 It is not a single condition, but a collection of disorders causing similar symptoms of abdominal pain and abnormal bowel habit. Food intolerance is a recognised exacerbating factor of IBS and may affect as many as 50% of patients.2, 3 However, there is no evidence of food allergy.4 A range of fermentable substrates may provoke gastrointestinal symptoms,5, 6 as may inhibitors of carbohydrate digestion.7 IBS frequently follows gastroenteritis8 or use of antibiotics,9 and the gut flora has been shown to be unstable.10 We postulated that abnormal colonic fermentation could be a factor in the pathogenesis of IBS. We investigated this hypothesis by assessing rates and patterns of colonic-gas production on standard and exclusion diets.

Section snippets

Methods

Patients with IBS fulfilling the Rome criteria1 were recruited from outpatients. Other gastrointestinal diseases were excluded by blood and stool analysis, sigmoidoscopy, lactose-hydrogen breath test, and, in patients older than 40 years, by barium enema. Controls came from a group of symptom-free individuals recruited for dietary studies. Exclusion criteria were previous gastrointestinal disease, and the use of laxatives, antibiotics, or other medication within the preceding 6 weeks. All

Results

Six female patients and six female controls took part. The median age of the patients was 45 years (IQR 42–58) of the controls 53 (51–54). All patients experienced stool frequency and looseness with abdominal pain on a daily basis. None showed evidence of anxiety before entry into the study, as assessed by the Eysenck personality questionnaire. One of each group admitted single violations of their diets, both more than 1 week before calorimetry.

On the standard diet, IBS patients excreted

Discussion

Our findings are consistent with the suggestion that the IBS may be caused by abnormal colonic fermentation. Maximum rates of gas excretion (mainly hydrogen) were much greater in IBS patients than in controls. On an exclusion diet, which significantly improved symptoms, gas excretion (hydrogen and methane) fell dramatically, but no such change occurred in controls.

Changes in hydrogen excretion do not result from differences in the rate of expulsion of gas after production, because the relation

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