The idea of deriving health benefits from live microorganisms is well known, but some non-living microorganisms, too, can have beneficial health effects. Yet even with an increasing number of scientific papers published on non-viable microbes for health, the category is not well defined and different terms are used in different contexts.
Now, a group of international experts has clarified this concept in a recently published scientific consensus definition in Nature Reviews Gastroenterology & Hepatology. The authors use an established term --postbiotics-- and precisely define it as "a preparation of inanimate microorganisms and/or their components that confers a health benefit on the host".
According to the definition, postbiotics may include either whole microbial cells or components of the cells, as long as they have somehow been deliberately inactivated.
Professor Seppo Salminen, lead author on the publication, says the group of experts -- from across the disciplines of probiotics and postbiotics, adult and pediatric gastroenterology, pediatrics, metabolomics, regulatory affairs, microbiology, functional genomics, cellular physiology and immunology -- wanted to clarify that postbiotics are more complex than the common idea of 'heat-killed probiotics'.
"With this definition of postbiotics, we wanted to acknowledge that different live microorganisms respond to different methods of inactivation," says Prof. Salminen. "Furthermore, we used the word 'inanimate' in favor of words such as 'killed' or 'inert' because the latter could suggest the products had no biological activity."
The authors emphasize that a postbiotic does not need to be derived from a probiotic. That is, scientists do not have to show that the live precursor microorganism itself has a health benefit before using it to create a postbiotic.
The definition was discussed at a panel convened by the International Scientific Association for Probiotics and Prebiotics (ISAPP) in late 2019. This published definition is the latest in a series of international consensus definitions by ISAPP: probiotics, prebiotics, synbiotics, fermented foods and postbiotics.
Mary Ellen Sanders, ISAPP's Executive Science Officer, says, "This was a challenging definition to settle. There are some who think that any purified component from microbial growth should be considered to be a postbiotic, but the panel clearly felt that purified, microbe-derived substances, for example, butyrate or any antibiotic, should just be called by their chemical names. We are confident we captured the essential elements of the postbiotic concept, allowing for many innovative products in this category in the years ahead."
Postbiotics have long been on the market in Japan, and fermented infant formulas with postbiotics are commercially available in South America, the Middle East, and some European countries. Given the scientific groundswell, postbiotic applications are likely to expand quickly.
Sanders says, "The definition will be a touchstone for scientists, both in academia and industry, as they work to develop products that benefit host health in new ways. We hope this clarified definition will be embraced by all stakeholders, so that when the term 'postbiotics' is used on a product, consumers will know what to expect."
Nature Reviews Gastroenterology & Hepatology