ABNORMAL COLONIC FERMENTATION IN IRRITABLE-BOWEL-SYNDROME

Background The cause of irritable bowel syndrome (IBS) is unknown. It may follow gastroenteritis and be associated with an abnormal gut flor a 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 ex clusion diet matched for macronutrients in six female IBS patients and six female controls. During the final 72 h on each diet, faecal excre tion of fat, nitrogen, starch, and non-starch polysaccharide NSP was m easured, and total excretion of hydrogen and methane collected over 24 h in a purpose-built 1.4 m(3) whole-body calorimeter. Breath hydrogen and methane excretion were then measured for 3 h after 20 g oral lact ulose. Findings The maximum rate of gas excretion was significantly gr eater 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 pat ients, the exclusion diet reduced symptoms and produced a fall in maxi mum gas excretion (0.5 mL/min IQR 0.3-0.7). After lactulose, breath hy drogen was greater on the standard than on the exclusion diet. Interpr etation Colonic-gas production, particularly of hydrogen, is greater i n patients with IBS than in controls, and both symptoms and gas produc tion are reduced by an exclusion diet. This reduction may be associate d with alterations in the activity of hydrogen-consuming bacteria. Fer mentation may be an important factor in the pathogenesis of IBS.