DIETARY MODULATION OF THE HUMAN COLONIC MICROBIOTA - INTRODUCING THE CONCEPT OF PREBIOTICS

Because the human gut microbiota can play a major role in host health, there is currently some interest in the manipulation of the compositi on of the gut flora towards a potentially more remedial community. Att empts have been made to increase bacterial groups such as Bifidobacter ium and Lactobacillus that are perceived as exerting health-promoting properties. Probiotics, defined as microbial food supplements that ben eficially affect the host by improving its intestinal microbial balanc e, have been used to change the composition of colonic microbiota. How ever, such changes may be transient, and the implantation of exogenous bacteria therefore becomes limited. In contrast, prebiotics are nondi gestible food ingredients that beneficially affect the host by selecti vely stimulating the growth and/or activity of one or a limited number of bacterial species already resident in the colon, and thus attempt to improve host health. Intake of prebiotics can significantly modulat e the colonic microbiota by increasing the number of specific bacteria and thus changing the composition of the microbiota. Nondigestible ol igosaccharides in general, and fructooligosaccharides in particular, a re prebiotics. They have been shown to stimulate the growth of endogen ous bifidobacteria, which, after a short feeding period, become predom inant in human feces. Moreover, these prebiotics modulate lipid metabo lism, most likely via fermentation products. By combining the rational e of pro- and prebiotics, the concept of synbiotics is proposed to cha racterize some colonic foods with interesting nutritional properties t hat make these compounds candidates for classification as health-enhan cing functional food ingredients.