Probiotics : Their Potential to Impact Human Health

Probiotics—live microorganisms that when administered in adequate amounts confer a health benefit on the host—have been studied for both human and animal applications, and worldwide research on this topic has accelerated in recent years. This paper reviews the literature on probiotics, describes how probiotics work in human ecosystems, and outlines the impact of probiotics on human health and disease. The paper also addresses safety issues of probiotic use, suggests future developments in the field of probiotics, and provides research and policy recommendations. Product considerations and potential future developments regarding probiotics also are discussed. The authors conclude that controlled human studies have revealed a diverse range of health benefits from consumption of probiotics, due largely to their impact on immune function or on microbes colonizing the body. Additional, well-designed and properly controlled human and mechanistic studies with probiotics will advance the essential understanding of active principles, mechanisms of action, and degree of effects that can be realized by specific consumer groups. Recommendations include establishment of a standard of identity for the term “probiotic,” adoption of third-party verification of label claims, use of probiotics selectively in clinical conditions, and use of science-based assessment of the benefits and risks of genetically engineered probiotic microbes. IntroductIon Probiotics1 are live microorganisms that when administered in adequate amounts confer a health benefit on the host (UNFAO/WHO 2001). Probiotics commonly are isolated from human and animal intestinal tracts. Dead bacteria, products derived from bacteria, or end products of bacterial growth also may impart certain benefits, but these derivatives are not considered to be probiotics because they are not alive when administered. Native bacteria are not probiotics until the bacteria are isolated, purified, and proved to have a health benefit when administered. Probiotics have been This material is based upon work supported by the United States Department of Agriculture under Grant No. 2005-38902-02319, Grant No. 2006-38902-03539, and Grant No. 2007-31100-06019/ISU Project No. 413-40-02. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or Iowa State University. Scanning electron micrographs (clockwise from upper left) of Lactobacillus paracasei, Lactobacillus plantarum, Streptococcus thermophilus, Bifidobacterium infantis, Bifidobacterium longum, and Bifidobacterium breve. (Photos courtesy of Prof. Lorenzo Morelli, Instituto di Microbiologia, Piacenza, Italy.) 1 Italicized terms (except genus and species names) are defined in the Glossary.