Effects of Probiotics and Prebiotics Prebiotics , Probiotics , and Synbiotics Affect Mineral Absorption , Bone Mineral Content , and Bone Structure 1 – 3

Several studies in animals and humans have shown positive effects of nondigestible oligosaccharides (NDO) on mineral absorption and metabolism and bone composition and architecture. These include inulin, oligofructose, fructooligosaccharides, galactooligosaccharides, soybean oligosaccharide, and also resistant starches, sugar alcohols, and difructose anhydride. A positive outcome of dietary prebiotics is promoted by a high dietary calcium content up to a threshold level and an optimum amount and composition of supplemented prebiotics. There might be an optimum composition of fructooligosaccharides with different chain lengths (synergy products). The efficacy of dietary prebiotics depends on chronological age, physiological age, menopausal status, and calcium absorption capacity. There is evidence for an independent probiotic effect on facilitating mineral absorption. Synbiotics, i.e., a combination of probiotics and prebiotics, can induce additional effects. Whether a low content of habitual NDO would augment the effect of dietary prebiotics or synbiotics remains to be studied. The underlying mechanisms are manifold: increased solubility of minerals because of increased bacterial production of short-chain fatty acids, which is promoted by the greater supply of substrate; an enlargement of the absorption surface by promoting proliferation of enterocytes mediated by bacterial fermentation products, predominantly lactate and butyrate; increased expression of calcium-binding proteins; improvement of gut health; degradation of mineral complexing phytic acid; release of bone-modulating factors such as phytoestrogens from foods; stabilization of the intestinal flora and ecology, also in the presence of antibiotics; stabilization of the intestinal mucus; and impact of modulating growth factors such as polyamines. In conclusion, prebiotics are the most promising but also best investigated substances with respect to a bone-health-promoting potential, compared with probiotics and synbiotics. The results are more prominent in animal models, where more studies have been performed, than in human studies, where experimental conditions are more difficult to control. J. Nutr. 137: 838S–846S, 2007. Accumulating knowledge prompted the scientific community to continually adapt the definitions of probiotics, prebiotics, and synbiotics. Probiotics are ‘‘viable, defined microorganisms in sufficient numbers, which alter the microflora in a compartment of the host and by that exert beneficial health effects in this host’’ (1). Recently it was demonstrated that live and nonviable microorganisms were equally effective to ameliorate experimentally induced colitis because the effect was mediated via the probiotics’ DNA rather than by their metabolites or ability to colonize the colon (2). This demonstrated that viability might be a prerequisite in the prevention or amelioration of some but not all disabilities (3). Prebiotics are nondigestible food ingredients that beneficially affect the host by selectively stimulating the growth and/or activity of 1 or a limited number of bacteria (probiotics) in the gastrointestinal tract and thereby exert a health-promoting effect (4). A synbiotic is a product containing prebiotics and probiotics and in which the prebiotic compound selectively favors the probiotic compound (1). The following 1 Published as a supplement to The Journal of Nutrition. The articles included in this supplement are derived from presentations and discussions at the World Dairy Summit 2003 of the International Dairy Federation (IDF) in a joint IDF/FAO symposium entitled ‘‘Effects of Probiotics and Prebiotics on Health Maintenance—Critical Evaluation of the Evidence,’’ held in Bruges, Belgium. The articles in this publication were revised in April 2006 to include additional relevant and timely information, including citations to recent research on the topics discussed. The guest editors for the supplement publication are Michael de Vrese and J. Schrezenmeir. Guest Editor disclosure: M. de Vrese and J. Schrezenmeir have no conflict of interest in terms of finances or current grants received from the IDF. J. Schrezenmeir is the IDF observer for Codex Alimentarius without financial interest. The editors have received grants or compensation for services, such as lectures, from the following companies that market proand prebiotics: Bauer, Danone, Danisco, Ch. Hansen, Merck, Müller Milch, Morinaga, Nestec, Nutricia, Orafti, Valio, and Yakult. 2 Author disclosure: no relationships to disclose other than that mentioned in Footnote 3. 3 This work was supported in part by ‘‘Forschungsschwerpunkt Muskelund Skelettsystem,’’ Kiel, Germany, and by Nestle Research Centre, Lausanne,