Research summary
Prebiotics vs Probiotics
Probiotics and prebiotics are often grouped together, but consensus definitions from the International Scientific Association for Probiotics and Prebiotics (ISAPP) draw a clear line between them. A probiotic is a live microorganism that, in adequate amounts, confers a health benefit on the host. A prebiotic is not a microorganism at all; it is a substrate that is selectively utilized by host microorganisms to confer a health benefit. The simplest way to remember the difference is that probiotics are the microbes themselves, prebiotics are what feed or are used by those microbes, and a product containing both is called a synbiotic.[1], [2]
What a probiotic is
In 2013 an expert panel convened by the International Scientific Association for Probiotics and Prebiotics (ISAPP) reviewed the field and reaffirmed the long-standing FAO/WHO definition of a probiotic as a live microorganism that, when administered in adequate amounts, confers a health benefit on the host. The panel judged that wording to be relevant and broad enough to cover current and anticipated applications, while clarifying inconsistencies in earlier FAO/WHO documents.[1]
Two features of this definition matter. First, a probiotic must be a living organism, not a substance or extract. Second, the consensus framed more precise use of the term as a way to help clinicians and consumers differentiate the diverse products on the market, rather than as evidence that any specific strain or product produces a particular effect.[1]
What a prebiotic is
A separate ISAPP expert panel convened in December 2016 updated the definition of a prebiotic to a substrate that is selectively utilized by host microorganisms conferring a health benefit. This is fundamentally different from a probiotic: a prebiotic is the material that microbes act upon, not a live microbe. The consensus retained the requirement for a selective, microbiota-mediated mechanism and stated that a beneficial health effect must be documented for a substance to qualify.[2]
The 2017 consensus also broadened the concept of prebiotics so that it can potentially include non-carbohydrate substances, applications at body sites beyond the gastrointestinal tract, and categories other than food. Even with that wider scope, the defining idea is unchanged: a prebiotic is a substrate selectively used by host microorganisms, which is why it sits on the opposite side of the line from a live probiotic.[2]
Probiotic, prebiotic, and synbiotic side by side
Putting the two consensus definitions together gives a clear contrast: probiotics are the live microorganisms themselves, while prebiotics are substrates selectively utilized by host microorganisms. A product that combines a probiotic with a prebiotic is referred to as a synbiotic. In each case the consensus definitions describe what the terms mean and embed a documented-health-benefit requirement; they are about terminology and labeling rather than a guarantee of any particular outcome from a specific product.[1], [2]
A practical memory aid is that probiotics are the microbes, prebiotics are what those microbes selectively use, and synbiotics pair the two. This framing reflects how the scientific association intends the terms to be used in research, marketing, and regulatory oversight so that the categories stay consistent and clear.[1], [2]
Limitations
This article reports definitional consensus, not clinical outcomes. The ISAPP statements establish what the terms probiotic and prebiotic mean; they do not demonstrate that any particular product, strain, or substrate produces a specific health effect, and any benefit depends on the individual product and the evidence behind it.[1], [2]
Because both definitions require a documented health benefit, classifying a substance as a probiotic or prebiotic is conditional on supporting evidence for that substance. The definitions also continue to evolve as science advances, and they are general statements rather than medical advice for any individual.[1], [2]
References
- Expert consensus document. The International Scientific Association for Probiotics and Prebiotics consensus statement on the scope and appropriate use of the term probiotic. Nature Reviews Gastroenterology & Hepatology. 2014. Expert consensus statement View source →
- Expert consensus document: The International Scientific Association for Probiotics and Prebiotics (ISAPP) consensus statement on the definition and scope of prebiotics.. Nature reviews. Gastroenterology & hepatology. 2017. Expert consensus statement View source →