probiotics is live microorganisms that, when administered in adequate amounts, confer a health benefit on the host. Other definitions advanced through the years have been restrictive by specification of mechanisms, site of action, delivery format, method, or host. Probiotics have been shown to exert a wide range of effects. The mechanism of action of probiotics (e.g., having an impact on the intestinal microbiota or enhancing immune function) was dropped from the definition to encompass health effects due to novel mechanisms and to allow application of the term before the mechanism is confirmed. Physiologic benefits have been attributed to dead microorganisms .furthermore, certain mechanisms of action (such as delivery of certain enzymes to the intestine) may not require live cells. However, regardless of functionality, dead microbes are not probiotics.
The term “probiotic” is sometimes erroneously used as a synonym for putatively beneficial members of commensal microbiota. The context for this misuse is the assertion that certain dietary or environmental factors may “encourage your native probiotics.” Members of human commensal microbiota are often sources from which probiotics are isolated, but, until such strains are isolated and then adequately characterized for content, stability, and health effects, they are not probiotics.