UPDATE ON PREBIOTICS

The human colonic microflora has a central role in health and disease, being unique in its complexity and range of functions. As such, dietary modulation is important for improved gut health.. Diet can affect the composition of the gut microflora through the availability of different substrates for bacterial fermentation. As such, functional food ingredients such as prebiotics could effect a beneficial modification in the composition and activities of gut microflora by increasing positive flora components. The prebiotic approach aims to increase resident bacteria that are considered to be beneficial for human health, e.g. bifidobacteria and lactobacilli. A prebiotic was originally defined, Dr Robertfroid, in 1995 as a "non-digestible food ingredient that beneficially affects the host by selectively stimulating the growth and/or activity of one or a limited number of bacteria in the colon, and thus improves host health"[.A more recent definition from FAO , stated that "A prebiotic is a selectively fermented ingredient that allows specific changes, both in the composition and/or activity in the gastrointestinal microbiota that confers benefits upon host wellbeing and health". The principal concept associated with both of these definitions is that the prebiotic has a selective effect on the microbiota that results in an improvement in health of the host. The definitions arose from observations that particular dietary fibres bring about a specific modulation of the gut microbiota, particularly increased numbers of bifidobacteria and/or lactobacilli, and that ingestion of these compounds was associated with improved host health. Overall, saccharolytic fermentation leads to the formation of end products (SCFA) that are recognised as being beneficial to the host. It is recognised that there are numerous potential new applications being considered for prebiotic use e.g. prevention and or management of type 2 diabetes mellitus; drug bioavailability; effects on autoimmune diseases and allergy; modulation of pathogenic biofilms. Common prebiotics in use include inulin, fructo-oligosaccharides (FOS), galactooligosaccharides soya-oligosaccharides, xylo-oligosaccharides, isomalto-oligosaccharides and lactulose. The majority of studies have so far focused on inulin, FOS and GOS. These saccharides have now a long history of safe use and are generally regarded as safe, There is also a range of new prebiotic compounds emerging, and these include: gluco- oligosaccharides, le