What health benefits do prebiotics have

Health benefits of prebiotics

Worldwide, there has been a growing awareness of the relationship between diet and health that has led to an increasing demand for food products that support health beyond simply providing basic nutrition. Incorporation of prebiotics and probiotics into foods can yield health benefits in the gastrointestinal tract and other parts of the body that are linked via the immune system.

Prebiotics have been shown to both promote the growth of healthy bacteria in the large bowel and to prevent the symptoms associated with bowel disorders, including irritable bowel disease and irregular bowel function. More recently prebiotics, in particular fructooligosaccharides (FOS) and galacto-oligosaccharides (GOS), have been reported to have significant health benefits in relation to anti-cancer properties, and influence on mineral absorption, lipid metabolism, and anti-inflammatory effects.

Commercially available prebiotics

Prebiotics are usually polysaccharides or oligosaccharides. Commonly used prebiotics include inulin, fructo-oligosaccharides (FOS), galacto-oligosaccharides (GOS), soya-oligosaccharides, xylo-oligosaccharides, pyrodextrins, isomalto-oligosaccharides and lactulose. Other prebiotics include pecticoligosaccharides, lactosucrose, sugar alcohols, gluco-oligosaccharides, levans, resistant starch, xylosaccharides and soy-oligosaccharides.

Mechanism of action of prebiotics

Prebiotics have been shown to be neither hydrolysed nor absorbed in the upper part of the gastrointestinal tract. Once the prebiotic enters the lower part of the gastrointestinal tract the prebiotic selectively stimulates the growth and/or activity of desirable bacteria in the colon. There are a number of desirable bacteria in the colon including species of lactobacillus and bifidobacteria which have been linked to a number of health benefits both within the digestive tract and in other organs of the body. Researchers have suggested that these bacteria protect the host by competing with bacterial or fungal pathogens for available nutrients and space and modulating the immune system. In addition, it has been reported that some short chain fatty acids (SCFA) including acetic, propionic and butyric acids are released during the fermentation of the prebiotic, and can serve as an energy source for the mucosal cells.

Qualitative and quantitative assessment of prebiotics

Roberfroid stated that for a material to be considered to be a prebiotic it should meet terms of a qualitative assessment of particular characteristics. This assessment requires the property of non-digestibility, which includes resistance to gastric acidity, hydrolysis by mammalian enzymes and gastrointestinal absorption. In addition there is a requirement for capacity for fermentation by intestinal microbes, and selective stimulation of growth and/or activity of intestinal bacteria.

When reviewing the existing methodologies for the qualitative assessment for classification of a prebiotic, only two dietary non-digestible oligosaccharides fulfilled all the required criteria for classification as a prebiotic. Roberfroid further proposed use of a quantitative score, termed the Prebiotic Index (PI), as a simple method to assess whether a food ingredient is a prebiotic. The PI was originally developed by Palframen et al. to assess the functionality of the material of interest. Those researchers defined the PI as the increase in bifidobacteria (expressed as the absolute number of new cfu/g of faeces) divided by the daily dose (in grams) of prebiotic ingested. Roberfroid subsequently defined the PI as [(Bif/Total) – (Bac/Total) + (Lac/Total) – (Clos/Total)], where 'Bif' is the number of bifidobacteria at sample time/numbers at inoculation, 'Bac' is the number of bacteroides at sample time/numbers at inoculation, 'Lac' is the number of lactobacilli at sample time /numbers at inoculation, 'Clos' is the number of clostridia at sample time/numbers at inoculation, and 'Total' is the total bacterial numbers at sample time/numbers at inoculation.

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