Pharmacists are familiar with probiotics and prebiotics, but what is a synbiotic? A consensus statement helped answer this question as it provided guidance and clarity on the appropriate use of this term.

This consensus statement was developed by the International Scientific Association for Probiotics and Prebiotics (ISAPP). The ISAPP, a nonprofit, volunteer, international collaborative made up scientists and academicians advancing the science around the use of prebiotics and probiotics, is funded by manufacturers of these products. 

The intent of this consensus statement is to clearly define a “synbiotic”; describe appropriate experimental conditions to help determine their effect; define the evidence for their potential health benefit as well as adverse events; and to provide guidance to researchers, industry, public health professionals, consumers, regulatory agencies, and the media on the use of these products. 

The consensus statement starts by defining a probiotic as “live microorganisms that, when administered in adequate amounts, confer a health benefit on the host” and a prebiotic as “a substrate that is selectively utilized by host microorganisms conferring a health benefit.” Adding to these definitions, The ISAPP defines a synbiotic as “a mixture comprising live organisms and substrate(s) selectively utilized by host microorganisms that confers a health benefit on the host.” Low doses of components of a synbiotic may not independently exert a health benefit until they are combined, or the microorganisms in a probiotic may require a prebiotic in order to be to beneficial. The ISAPP further classified synbiotics as complementary or synergistic.

A complementary synbiotic is a mixture of a probiotic and a prebiotic that meet their respective definitions. The probiotic strain would be selected based on the benefits that it provides in the host, whereas the prebiotic helps promote the growth and function of the microbiota while providing a health benefit. A synergistic synbiotic contains a substrate that is designed to be selectively utilized by the coadministered microorganisms. In this case, the live microorganism is chosen based on its ability to provide a health benefit and the substrate is selected to mainly support the growth or activity of the selected microorganism. 

According to the ISAPP, there are minimum criteria that both types of synbiotics must meet, including that they must be safe for their intended use; their live microbial components should be characterized and their genomic sequence made publicly available; they should possess a scientifically valid name; the strain of microorganism utilized should be identified; the microorganism should be deposited in the international culture collection to provide access to verify testing results; they should possess activity that is linked to the microbiota; they should be studied in the target host with demonstration of health benefit; and their proper condition for use should be clearly described. However, there are also differences in the minimum criteria between the two types of synbiotics. 

Additional minimum criteria for a complementary synbiotic include that there is selective utilization of the substrate by the resident microbiota; however, selective utilization by the coadministered live microorganism is not required as it is for a synergistic synbiotic. Further, studies in the target host demonstrating the selective use of the substrate are not needed for a complementary synbiotic. On the other hand, whereas selective utilization of a substrate by the resident microbiota is not required for a synergistic synbiotic, studies are needed regarding the selective utilization of the substrate in the target host for this type of synbiotic. 

The ISAPP states that while term synbiotic is currently not widespread, its use is growing. Since the inception of the term in 1995, there has been a subtle increase in the number of publications mentioning synbiotics with the latest results from 2019 indicating 269 citations in that year. 

As these products become more widely available, pharmacists need to be familiar with their components and the criteria that have gone into defining their health benefits in order to adequately recommend and advise patients about their proper use.

The content contained in this article is for informational purposes only. The content is not intended to be a substitute for professional advice. Reliance on any information provided in this article is solely at your own risk.

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