Exp Clin Endocrinol Diabetes 2005; 113 - 7
DOI: 10.1055/s-2005-862866

Beneficial effects of dietary wheat and oat fibre are independent of colonic fermentation

MO Weickert 1, M Möhlig 1, C Koebnick 2, MA Osterhoff 1, M Ristow 1, H Rochlitz 1, N Rudovich 1, J Spranger 1, AFH Pfeiffer 1
  • 1German Institute of Human Nutrition, Potsdam-Rehbruecke, Charité – Campus Benjamin Franklin, Berlin
  • 2German Institute of Human Nutrition, Intervention Studies, Potsdam-Rehbruecke

Background: Low GI diets are known to improve health. In contrast to soluble dietary fibres, insoluble fibres have no acute impact on postprandial glucose and insulin responses. However, in population studies diets rich in insoluble dietary fibre are associated with a reduced risk of diabetes and CHD. Possible mechanisms might be colonic fermentation of insoluble dietary fibre with the production of metabolic active substrates.

Objective: The aim of this study was to investigate whether the consumption of commercially available insoluble wheat and oat fibres baked in bread have acute effects on plasma glucose and insulin responses.

Material and Methods: The study was carried out in a randomized single-blind crossover design. 14 healthy women with NGT were studied on 6 occasions after 10h overnight fasts. Subjects recorded their diet and ate identically before each study day. On days 1, 3 and 5 subjects consumed 3 isoenergenic portions of white bread (A) or test-bread (10.5g wheat-fibre(B), 10.6g oat-fibre(C)) with the same amounts of available carbohydrates (50g), protein and fat. On days 2, 4 and 6 subjects consumed control bread (A).

Results: A day after the consumption of dietary wheat or oat fibre significant lower glucose values were measured (AUC 2849.1±331, p=0.021 (B), AUC 2833.7±277, p=0.024 (C) compared to the control values (AUC 4000.2±431). There were no differences in acute glycemic responses, in acute or second day effects on AUC insulin levels or C-Peptide/Insulin-ratios, but an earlier postprandial hyperinsulinemia (p=0.039). The estimated gut transit times were the same. Fermentation measured by the breath H2 test was significant only after the consumption of bread C (p=0.017).

Conclusions: We observed an improved glucose response associated with an earlier peak in insulin response the day after consumption of both processed dietary wheat and oat fibre baked in white bread. The reason for this improvement remains unclear, but seems to be independent of colonic fermentation, since only the oat fibre bread showed significant increases in hydrogen in the breath tests.