About Dietary Fibre
Dietary fibre is considered the portion of plant cells that are resistant to hydrolysis and human digestion. This allows the fibre to reach the colon undigested, allowing fermentation by the micro flora. Inulin is metabolised in the gut the same way as dietary fibre. Since they are not absorbed in the small intestine, calorie value is significantly lower then carbohydrates. As a result of the dietary fibre reaching the colon, there is an increase in biomass. If appropriate liquid intake is met to stay hydrated, the fibres are able to ferment. This results in increased fecal bulk and frequency, promoting regularity and alleviating constipation.
All Prebiotics Are Dietary Fibre
As previously mentioned, dietary fibre is considered a carbohydrate that is not hydrolyzed, nor digested, in the small intestine. All currently established prebiotics fit into this concept of dietary fibre.
Prebiotics resist digestion in the small intestine, are fermented in the large intestine, contain less energy in the form of calories than starch and sucrose, and increase stool weight and frequency. However, not all dietary fibres are prebiotic. By definition, prebiotics are a non-digestible food ingredient that improves human health by its selective fermentation by one or a limited number of beneficial bacteria entirely by the colonic flora, and stimulating their growth and/or activity. Dietary fibres can be classified into soluble and non-soluble fibres. Soluble dietary fibres are fermented, but usually not in a selective way (Prebiotics fibres are fermented in a selective way, meaning not all soluble dietary fibres are prebiotic). Non-soluble dietary fibres are not fully fermented by the colonic flora (Prebiotics are fully fermented by the colonic flora. Since some non-soluble dietary fibre is fermented outside the colon, not all non-soluble dietary fibre are prebiotic). Therefore, not all dietary fibres are prebiotic.