In vitro model to correlate viscosity and bile acid-binding capacity of digested water-soluble and insoluble dietary fibres

Binding and excretion of bile acids in the small intestine by water-soluble and insoluble dietary fibres is one of the main mechanisms for their cholesterol-lowering effects. A model for the determination of the bile acid-binding capacity of dietary fibres was developed. The experimental set-up allowed to correlate the bile acid-binding capacities of different fibres with their viscosities after in vitro digestion. For cellulose, native oat fibre and psyllium fibres clear correlations between viscosity and bile acid-binding capacity could be observed, whereas for water-insoluble lupin fibre such a correlation did not exist. Heat-damaged oat fibre also showed bile acid-binding despite of significantly decreased viscosity. The data demonstrated that bile acid-binding of digested dietary fibres may not be solely based on their viscosity but may be influenced by additional binding forces.