Interactions between dietary fibre-rich preparations and glycoconjugated bile acids in vitro

Binding in small intestine and excretion of bile acids constitute a major hypocholesterolemic pathway. Interactions between different types of commercial and laboratory-made dietary fibres and glycoconjugated bile acids were investigated in vitro at pH 5.0 and 6.5. The interactions were greater at the lower pH and with dihydroxy-bile acids. Digested cereal products (barley, oat, rye and wheat flour; oat bran), alcohol-insoluble substances from apples, strawberries, rowan berries, carrots, white cabbage, red beets and sugar beet pulp, as well as arabinoxylan, bound 1.21–1.77 μmol bile acids/100 mg of preparation at pH 5.0. Novelose bound approximately 0.65 μmol bile acids/100 mg. Carob fibre had the highest binding capacity (1.83–1.96 μmol bile acids/100 mg) whereas cellulose had no effect. Besides the source and chemical composition, the bile acid binding correlated especially well with the presence of three-dimensional cell wall structures of the tested preparations but less well with the proportions of soluble and insoluble dietary fibre.