On the second day of the 2016 GMFH meeting, several speakers addressed the topic of the definition of probiotics. To my surprise, some of the speakers seemed to be unclear about the definition of a probiotic.
A widely accepted definition of probiotics was developed by an expert consultation convened by FAO/WHO in 2001. This definition was affirmed in 2014 in a consensus panel paper published by Hill, et al. in Nature Reviews Gastroenterology and Hepatology. Probiotics are defined as live microorganisms that, when administered in adequate amounts, confer a health benefit on the host.
This definition seems clear to me. However, some suggested that a different term should be used instead. One such term is ‘pharmabiotic’. An alimentary pharmabiotic was defined by Shanahan, et al. (2009) as “any material with potential health benefit that can be mined from host–microbe–dietary interactions in the gut.” The ‘pharma’ in the term suggests that a pharmabiotic is a drug, not a food, including the expected levels of scientific substantiation. The term pharmabiotic encompasses a broader set of substances, including live and dead microbes, microbial components, and microbe-produced substances. However, in other ways, this term is more limited. It requires that the substance emanate from host–microbe–dietary interactions in the gut. So whereas a probiotic must be a live microbe, its mode of action is not restricted by the definition. Also, pharmabiotic has been exclusively used in the context of the gut, whereas probiotic is not so limited.
Another misconception is that probiotics are the same thing as live biotherapeutic agents. The term ‘live biotherapeutic agent’ is used by the FDA in the United States to refer to live organisms used as drugs. As is clearly demonstrated in Figure 3 of Hill, et al., probiotics span the range of regulatory categories, of which drugs is only one. So in the United States, a probiotic drug is equivalent to a live biotherapeutic agent, but a probiotic food ingredient or dietary supplement is not.
Probiotic is a perfectly functional term, with broad scientific and increasingly broad consumer understanding (see here and here). When referring to a live microbe administered for a health effect, the term probiotic is both precise and clear. When referring to a broader range of microbial-derived substances, the term pharmabiotic may be more suitable. Shanahan, et al. imply that ‘probiotic’ has outlived its usefulness and advocate for exclusive use of the term pharmabiotic “to avoid a multiplicity of technical terms.” However, I believe the term probiotic is established, uncontentious, accepted and useful. If the 22,000 downloads of the Hill paper are any testimony, many in the scientific community agree.