Dietary Fiber-Rich Barley Products Beneficially Affect the Intestinal Tract of Rats

Abstract

The objective of this study was to investigate the effects of barley-rich diets in the intestinal tract of rats. Four test groups (A-D) of 10 young male Wistar rats were fed diets containing 50 g/100 g barley extrudates (A, B and D) or mixtures (C) for 6 wk; the control diet contained no barley. The barley-containing supplements in the test diets were: A = cultivar "HiAmi"; B = "HiAmi" and "Prowashonupana" (50:50); C = "Prowashonupana" and Novelose (50:50); D = "Prowashonupana" and amylose from maize (60:40). These supplements contained 7-12 g/100 g beta-glucan and 7-24 g/100 g resistant starch. Additionally, 5 g microcrystalline cellulose/100 g was present in all diets. Carbohydrate utilization (indirect calorimetry) was lower (P < 0.05) in rats fed the barley-containing diets C or D than in the controls. In the test groups, the following differences from the controls were found: greater food intake in the last 2 wk (P < 0.05); increased weight gain in wk 6 (P < 0.05); greater mass of the ceca (groups B-D; P < 0.05) and colons (P < 0.001) as well as masses of cecal (groups C and D; P < 0.01) and colon contents (P < 0.001); greater concentrations of resistant starch in cecal and most of the colon contents (P < 0.05); and more beta-glucan in the small intestine, cecum and colon (P < 0.05). The numbers of coliforms and Bacteroides were lower than in the controls in groups B-D and those of Lactobacillus were greater in all test groups (P < 0.05). Short-chain fatty acids (SCFA) were higher in the cecal contents of the test groups (> or = 800 micro mol/g DM; P < 0.001) compared with the controls ( approximately 200 micro mol/g DM). Similarly, SCFA were higher in colon and feces of the test groups. The concentrations of excreted bile acids increased up to 30% during the feeding period. The proportions of secondary bile acids were lower and the amounts of neutral sterols (P < 0.001) were greater in feces of rats fed the barley-containing diets for 6 wk than in the controls. Diets containing more soluble macromolecular dietary fibers such as beta-glucans affected the excretion of bile acids and neutral sterols the most, whereas the fermentation of dietary fiber, including resistant starch, influenced the steroids in feces. These results suggest that dietary fiber-rich barley-containing diets have beneficial physiologic effects.