Differentiation of Adsorptive and Viscous Effects of Dietary Fibres on Bile Acid Release by Means of In Vitro Digestion and Dialysis

Abstract

To explain the cholesterol-reducing effects of dietary fibres, one of the major mechanisms proposed is the reduced reabsorption of bile acids in the ileum. The interaction of dietary fibres with bile acids is associated with their viscous or adsorptive effects. Since these fibre characteristics are difficult to investigate in vivo, suitable in vitro methodologies can contribute to understanding the mechanistic principles. We compared the commonly used centrifugal approach with a modified dialysis method using dietary fibre-rich materials from different sources (i.e., barley, citrus, lupin, and potato). Digestion was simulated in vitro with oral, gastric, and small intestinal digestion environments. The chyme was dialysed and released bile acids were analysed by high-performance liquid chromatography. The centrifugation method showed adsorptive effects only for cholestyramine (reference material) and a high-fibre barley product (1.4 µmol taurocholic acid/100 mg dry matter). Alternatively, the dialysis approach showed higher values of bile acid adsorption (2.3 µmol taurocholic acid/100 mg dry matter) for the high-fibre barley product. This indicated an underestimated adsorption when using the centrifugation method. The results also confirmed that the dialysis method can be used to understand the influence of viscosity on bile acid release. This may be due to entrapment of bile acids in the viscous chyme matrix. Further studies on fibre structure and mechanisms responsible for viscous effects are required to understand the formation of entangled networks responsible for the entrapment of the bile acids.

Associations between Dietary Patterns and Bile Acids—Results from a Cross-Sectional Study in Vegans and Omnivores

“…The absorption rate may also depend on the type of fiber; thus, cellulose showed a higher binding capacity than lignin [10], and, among vegetables, kale showed a high binding of bile acids [49] in vitro. The micelles are suggested to inhibit the re-absorption of bile acids [50], and to enhance their excretion in stool [47]. However, our findings of higher fecal bile acid concentrations in omnivores and higher serum bile acid levels in vegans do not support this hypothesis and further human studies are needed to clarify the relevance of this mechanism in vivo.…”

Development and Validation of a Questionnaire to Measure Adherence to the Mediterranean Diet in Korean Adults

“…Increased consumption of fiber from whole grains, legumes, vegetables, and fruits also leads to significant reductions in plasma LDL cholesterol levels [37]. Fibers prevent the reabsorption of bile acid in the ileum, therefore, serum cholesterol level are reduced [38]. Lastly, various phytochemicals, such as polyphenols, abundant in vegetables, fruits, and olive oil have anti-oxidant and anti-inflammatory effects that contribute to the prevention of CVD [33].…”

Plant Cell Walls: Impact on Nutrient Bioaccessibility and Digestibility

“…For example, cellulose has a hydrophobic binding capacity for certain molecules-e.g., polyphenols [85]. The cholesterol-reducing effect of certain water soluble dietary fibers, such as those found in oat (β-glucan), is proposed to arise from the sequestration of bile salts and excretion of the excess in feces [83,86]. The binding of amylase to cell wall components, and subsequent inhibition of the enzyme, has also been demonstrated in vitro [32,82].…”