Prebiotic effects of fermentable carbohydrate polymers may be modulated by faecal bulking of non-fermentable polysaccharides in the large bowel of rats

摘要

This study investigated the impact of supplementary fermentable polysaccharides inulin (a prebiotic) and barley β-glucan on the large bowel, when consumed against a background high or low intake of mixed non-starch polysaccharide. Rats were fed for 28 days with diets containing high (15%) and low (5%) background dietary fibre (BDF; cellulose plus sugar beet fibre), with or without 5% supplementary fermentable fibre (SFF; inulin or barley β-glucan). High-BDF diets unsupplemented with inulin or barley β-glucan caused greater improvement than supplemented low-BDF diets in several parameters linked to gut health: they increased colonic Bifidobacterium spp., butyric acid concentration in the caecum, and colonic crypt depth more than inulin and barley β-glucan. For these parameters, inulin and barley β-glucan added little to the effects of the high-BDF diet alone. Furthermore, by allowing for dilution due to the greater faecal bulk induced by the mixed fibre compared with inulin or barley β-glucan, the total quantity of butyric acid in the colon of BDF-fed rats was greatly amplified. Interpretation of the effects of prebiotics in diets containing dietary fibre requires concurrent analysis of the multiple effects of non-fermentable bulk.