British Journal of Nutrition

Human and Clinical Nutrition

Substrates available for colonic fermentation from oat, barley and wheat bread diets. A study in ileostomy subjects

Ågot Liaa1, Birgitta Sundberga2, Per Åmana2, Ann-Sofie Sandberga3, Göran Hallmansa4 and Henrik Anderssona1

a1 Department of Clinical Nutrition, University of Göteborg, Göteborg, Sweden

a2 Department of Food Science, Swedish University of Agricultural Sciences, Uppsala, Sweden

a3 Department of Food Science, Chalmers University of Technology, Göteborg, Sweden

a4 Department of Nutritional Research, University of Umeå, Sweden

Abstract

Nutrients not absorbed in the small bowel will form substrates for microbial growth in the colon which may have implications for the development of colon cancer. The aim of the present study was to investigate whether fibre-rich oat and barley diets increase the excretion of energy-supplying nutrients from the small bowel compared with a low-fibre wheat diet, and whether a possible. increase could be related to the β-glucan content. Nine ileastomy subjects were served four types of bread together with a low-fibre basal diet (12 g dietary fibre/d). The breads were based on either wheat flour (W diet, 7 g dietary fibre/d), oat bran (OB diet, 29 g dietary fibre/d), the same amount of oat bran with addition of β-glucanase (EC 3.2.1.4) (OBE diet, 19 g dietary fibre/d) or a fibre-rich barley fraction (B diet, 35 g dietary fibre/d). An increased ileal excretion of starch was observed with the barley diet but no effect of the oat β-glucan on starch recovery was found. The NSP + Klason lignin in the ileostomy effluents accounted only for 24, 31, 24 and 35% of the gross energy excretion in the W, OB, OBE and B diet periods respectively. A large part of the dry weight and energy (30, 21, 28 and 27%, in the W, OB, OBE and B diets respectively) in the effluents could not be identified as fat, protein, total starch or NSP + Klason lignin. This unidentified part was probably made up of oligosaccbarides, endogenous losses and nutrient complexes. Methods for identifying and analysing these components should be developed and their role as substrates for colonic fermentation and colon cancer development ought to be investigated.

(Received August 31 1995)

(Revised March 11 1996)

(Accepted April 05 1996)

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