Nutritional effects of dietary fibre-rich extrudates from oat in rats and man

Abstract

Cereal products are the most important source of dietary fibre (DF). The objective of this study was to evaluate physiological effects of DF-rich oatbased extrudates from the whole-grain type in vivo. A series of extrudates was prepared from whole-grain oat meal, oat bran and Novelose 330. These products differed in their contents of soluble and insoluble DF as well as of â-glucan and resistant starch. Rats (10 per group) were fed a control diet or test diets containing 50 % of these extrudates for 6 weeks. Further, 12 healthy human subjects consumed 100 g/day of an extrudate from oat meal and Novelose 330 (80/20) additionally to their habitual diet for 4 weeks. In dependence on the DF composition and concentration, higher formation and absorption of short-chain fatty acids (SCFA) were found in rats as a result of DF fermentation in the caecum and colon. Under the oat-based diets, the composition of the microflora and plasma lipid parameters were slightly changed. Caecum weights and caecal contents were higher in the test groups. In contrast to control, concentrations of bile acids (BA) and neutral sterols (NS) were greater in caecal and colonic contents as well as their excretion. The amount and proportion of secondary BA decreased as a result of lower pH values in intestinal contents of the experimental groups. Weight gain was not changed but rats of test groups consumed more water. The extrudate was well accepted by the human subjects. After 4 weeks of extrudate intake, concentrations of SCFA, including of butyrate, were increased in faeces. The higher DF consumption correlated with higher BA and NS concentrations in faeces. Most of these parameters reached their original levels 2 weeks after the experiment. Administration of DF-rich extrudates from whole-grain oatbased products results in beneficial physiological effects and may be helpful to increase the DF intake in humans. This work was supported by the FEI (Forschungskreis der Ernährungsindustrie e.V., Bonn), the AiF and the Ministry of Economics and Labour (Project No. 12716 BR).