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Probiotics are live microorganisms that confer a health benefit on the host when administered in appropriate amounts. Over 700 randomized, controlled, human studies have been conducted with probiotics thus far, with the results providing strong support for the use of probiotics in the clinical prevention or treatment of gastrointestinal tract disorders and metabolic syndrome. The present review is based on webinar presentations that were developed by the American Gastroenterological Association (AGA) in partnership with the International Scientific Association for Probiotics and Prebiotics (ISAPP) and the North American branch of the International Life Sciences Institute (ILSI North America). The presentations provided gastroenterologists and researchers with fundamental and current scientific information on the influence of gut microbiota on human health and disease, as well as clinical intervention strategies and practical guidelines for the use of probiotics and prebiotics.

uses of probiotics along with current knowledge of probiotic organisms, their properties, and their mechanisms of action. The program included scientific presentations about advances in understanding of the relationship between the gastrointestinal microbiota and the development of the innate and adaptive immune system, as well as the implications of this relationship for current uses of and research on probiotics (table 1). Unlike other workshops held to date, the program examined the critically important interface between science and regulation. Speakers addressed the impact that science has on the way in which products are regulated and the equally important impact that regulations have on how research is planned and conducted, how product information is conveyed to consumers and health care professionals, and how products are ultimately marketed. The articles and discussions in this supplement address these topics that were presented in each panel. This article summarizes the findings of the conference and the recommendations made for future directions relating to research on probiotics.

Interest in probiotics is at an all-time high in the United States, driven in part by new products emerging in the market, by US researchers eager to evaluate efficacy claims rigorously, and by consumers interested in potential therapeutic and preventive health benefits. The US marketplace is a mixed bag of products, some well-defined and properly evaluated in controlled clinical studies and others with unsubstantiated claims of efficacy. Validation of probiotic contents in commercial products is needed to ensure consumer confidence. The term "probiotic" should be used only for products that meet the scientific criteria for this term-namely, products that contain an adequate dose of live microbes that have been documented in target-host studies to confer a health benefit. Probiotics must be identified to the level of strain, must be characterized for the specific health target, and must be formulated into products using strains and doses shown to be efficacious. Several characteristics commonly presumed to be essential to probiotics, such as human origin and the ability to improve the balance of the intestinal microbiota, are discussed.

A large number of studies have investigated gastrointestinal microbiota and changes in the gastrointestinal community. However, a concern in these studies is how best to assess changes in gastrointestinal community structure. This paper presents two different human trials where the fecal terminal restriction fragment length polymorphism data sets were analyzed to search for treatment effects. Principle components analysis and cluster analysis based on grouped data are compared with analysis of data by subject using distance coefficients. Comparison with baseline within an individual before grouping by treatment provided a clearer indication of treatment effects than did an evaluation of data grouped before analysis. In addition, a large within-subject sample size and multiple baseline samples are necessary to accurately analyze treatment effects.