Cereal dietary fibres as prebiotics : metabolite production and health effects of arabinoxylan and β-glucan fermentation

Sammanfattning: The human gut is colonized by an enormous amount of microorganisms, the so called microbiota. The microbiota degrades dietary components in the colon and utilize them as substrates in their metabolism. Dietary fibres are the most important energy source for the microbiota. Some dietary fibres are classified as prebiotics, as they have the ability to alter the composition and activity of the microbiota and promote health benefits. Cereals are the major source of dietary fibres in Scandinavia. Among the cereals rye (Secale cereale) and oat (Avena sativa) are most frequently consumed as whole grains. The aim of this literature study was to review the current knowledge about the prebiotic properties of arabinoxylan and β-Glucan, the major dietary fibres in rye and oats. A prebiotic substrate is selective and confer health benefits. The result shows that arabinoxylan and β-Glucan fermentation display prebiotic properties. Both confer health benefits by indirectly stimulating beneficial metabolite production of the shortchain fatty acids acetate, propionate and butyrate. The literature shows that arabinoxylan particularly promotes butyrate production, while β-Glucan promotes propionate production and in some conditions butyrate as well. Butyrate has been shown to improve intestinal integrity, prevent inflammation and exhibit an anti-carcinogenic effect. Propionate inhibits cholesterol synthesis. However, health effects of dietary fibres can depend on the individual responsiveness to a substrate, the so-called enterotype. In general, a diet with various dietary fibres has been connected to health benefits, partly because it prevents production of detrimental metabolites that is formed in the absence of fermentable carbohydrates. Future studies will have to further confirm the prebiotic properties of arabinoxylan and β-Glucan in vivo with human subjects. If such studies would present enough scientific support for authority health claims, it may be a way to increase the consumption of dietary fibres in the population and contribute to improving public health.