Explain Mechanism for reduce the absorption of nutrients?

The absorption of nutrients is also reduced by mechanisms other than increasing the viscosity of gastrointestinal content. These mechanisms are:

• Soluble fibres (pectin, guar gum, oat bran), as well as, insoluble fibrelignin, may affect lipid absorption by their ability to adsorb fatty acids and cholesterol, thereby inhibiting their incorporation in miscelle. Further adsorption of bile acids to these fibres reduces the availability of bile acids for micelle formation.
• In case of unrefined whole plant material, the nutrients are sequestered within the cellular matrix and hence unavailable for absorption. Grinding of food material and thorough chewing can influence absorption.
• The altered mineral availability associated with diets high in fibre appear to be due to binding of metal ions. Fibres which possess uronic acid (pectin, hemicelluloses gum) can form cationic bridges with minerals. Lignin, with both carboxyl and hydroxyl groups, can absorb minerals. Certain constituents of plants e.g. phytates, silicates and oxalates also chelate divalent cations. However, the overall effect that a fibre will have on mineral balance will depend on the composition of diet and degree of fermentability of fibre. Rapidly fermentable fibres release the bound minerals as fermentation occurs and these minerals may possibly be absorbed in the colon.