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Research summary

Prebiotics vs Probiotics

Key takeaway

Consensus definitions distinguish probiotics from prebiotics: probiotics are live microorganisms that confer a health benefit in adequate amounts; prebiotics are substrates selectively utilized by host microorganisms that confer a health benefit. Both terms require supporting evidence of a benefit; the category name does not establish an effect for a particular retail product. A synbiotic combines live microorganisms with a substrate that host microorganisms selectively use, and the combination must confer a health benefit. Combining ingredients is not enough to establish that a product meets this definition.[1], [2], [3]

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]

This is a scientific definition, not evidence that any particular retail product produces a health benefit.[3]

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]

The distinction and its evidence requirement

Probiotics are live microorganisms; prebiotics are substrates selectively utilized by host microorganisms. Both definitions include a documented-health-benefit requirement. These categories do not guarantee a particular outcome from a specific retail product.[1], [2]

When a combination qualifies as a synbiotic

A synbiotic combines live microorganisms with a substrate that host microorganisms selectively use, and the combination must confer a health benefit. Combining ingredients is not enough to establish that a product meets this definition.[3]

References

  1. 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 →
  2. 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 →
  3. The International Scientific Association for Probiotics and Prebiotics (ISAPP) consensus statement on the definition and scope of synbiotics. Nature reviews. Gastroenterology & hepatology. 2020. Expert consensus statement View source →

Read the concise FAQ answer

Use the FAQ when you want the direct answer first, then return here for the full evidence context.

What is the difference between prebiotics and probiotics?

Probiotics are live microorganisms that confer a health benefit when administered in adequate amounts. Prebiotics are substrates selectively used by host microorganisms to confer a health benefit. Postbiotics are preparations of inanimate microorganisms and/or their components that confer a health benefit. A synbiotic combines live microorganisms with a substrate that host microorganisms selectively use, and the combination must confer a health benefit. Combining ingredients is not enough to establish that a product meets this definition.

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