Volume 90, Issue 5, November (2003), pp. 895-906 © The Author 2003
doi:10.1079/BJN2003976

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Steroids in the intestinal tract of rats are affected by dietary-fibre-rich barley-based diets

Gerhard Dongowski¹, Mario Huth¹, Erich Gebhardt^2
1Department of Food Chemistry and Preventive Nutrition, German Institute of Human Nutrition, Potsdam-Rehbrücke, Bergholz-Rehbrücke, Germany
²Institute of Nutritional and Environmental Research, Bergholz-Rehbrücke, Germany

 (Received 14 October 2002–Revised 27 May 2003–Accepted 7 July 2003)

The aim of the present study was to investigate the influence of dietary-fibre (DF)-rich barley-based diets on bile acids (BA) and neutral sterols (NS) in the intestinal tract of rats. For this purpose, young male Wistar rats (n 50; ten per group) weighing about 67 g were fed either a barley-free diet (control group) or diets containing 500 g barley meal extrudates/kg or a barley meal–Novelose mixture (groups A–D) for 6 weeks. These barley products contained 7–24 g resistant starch/100 g and 7–12 g (1→3),(1→4)-β-glucan/100 g. More steroids were transported towards the lower parts of the intestinal tract when higher concentrations of macromolecular DF were present in the diets (P<0·001). Tauroconjugated and primary BA dominated in the contents of the small intestine. Intense enzymic conversion of BA occurred in the caecum and colon. The fermentation of DF affected indirectly the amount of formed secondary BA. The main BA present in the caecal contents were muricholic acids, hyodeoxycholic acid and cholic acid. The BA spectrum in the colonic contents was different from that in the caecum. A higher concentration of NS appeared in the intestinal contents of the groups fed the barley-based diets than in the controls (P<0·005). The microbial conversion of cholesterol to coprostanol, cholestanone and coprostanone was influenced by the amount and composition of the DF in the gut. DF in the diet may affect the concentration and spectrum of steroids in the intestinal tract. The results are relevant for the discussion of mechanisms behind the cholesterol-lowering effects of DF.

Keywords:
Barley, β-Glucan, Resistant starch, Steroids

Abbreviations:
BA, bile acid, CA, cholic acid, CDCA, chenodeoxycholic acid, DCA, deoxycholic acid, DF, dietary fibre, HDCA, hyodeoxycholic acid, LCA, lithocholic acid, MCA, muricholic acid, NS, neutral sterol, RS, resistant starch, TCA, taurocholic acid, TCDCA, taurochenodeoxycholic acid