Probiotics and postbiotics are both increasingly used in microbiome-focused health products, but the regulatory and clinical considerations surrounding them can differ substantially. Probiotics depend on live microorganisms, making strain identity, viability, manufacturing controls, shelf-life stability, and population-specific safety central to product development. Postbiotics contain deliberately inactivated microorganisms and/or their cellular components that have demonstrated a health benefit, and therefore avoid some viability-related challenges, but introduce different questions around characterization, processing, batch consistency, and comparability to clinically studied preparations. This article examines the key regulatory, clinical, manufacturing, and evidence differences between probiotics and postbiotics and explains what manufacturers should consider when developing products and substantiating health claims.
As microbiome science continues to evolve, manufacturers are moving beyond traditional probiotics toward a wider range of products designed to influence interactions between microorganisms and the host.
Postbiotics have become one of the most significant emerging categories.
At first glance, the distinction appears relatively straightforward. Probiotics contain live microorganisms, while postbiotics contain inactivated microorganisms and/or their components. But from a regulatory and clinical perspective, that difference has consequences throughout the product development lifecycle.
For probiotics, maintaining and demonstrating microbial viability is fundamental. The identity of the microorganism, viable count, stability through shelf life, manufacturing conditions, and evidence supporting the specific strain can all affect whether a product and its claims are scientifically defensible.
Postbiotics remove the requirement for the microorganism to remain viable, but this does not necessarily make their regulatory pathway simpler. Instead, the focus shifts toward questions such as how the microorganism was inactivated, what remains in the final preparation, whether its composition and biological activity are reproducible, and whether the marketed product adequately represents the preparation used in supporting studies.
Understanding these differences early can help manufacturers develop stronger regulatory strategies, design more relevant clinical programs, and avoid relying on evidence that may not adequately support the finished product.
The widely accepted definition of a probiotic describes live microorganisms that, when administered in adequate amounts, confer a health benefit on the host.
Postbiotics are different.
The International Scientific Association for Probiotics and Prebiotics (ISAPP) defines a postbiotic as a “preparation of inanimate microorganisms and/or their components that confers a health benefit on the host.”
This means that simply killing a probiotic organism does not automatically create a postbiotic.
The resulting preparation must be sufficiently characterized and shown to confer a health benefit. Under the ISAPP definition, substantially purified microbial metabolites and substantially purified microbial components or products—including isolated proteins, peptides, exopolysaccharides, short-chain fatty acids and cell-free filtrates—do not qualify as postbiotics in their own right. A qualifying postbiotic is a characterized preparation containing inanimate microbial biomass, such as intact cells and/or cell fragments or components, with or without retained metabolites, and must have demonstrated a health benefit in the target host.
That distinction becomes important when manufacturers attempt to apply evidence generated for a live probiotic to an inactivated version of the same microorganism.
Inactivation can alter cellular structures, metabolites, proteins, and other biologically relevant components. Different inactivation methods can also produce materially different preparations.
As a result, evidence supporting a live probiotic should not automatically be assumed to substantiate a postbiotic derived from the same strain.
Neither “probiotic” nor “postbiotic” necessarily determines a product’s legal classification.
In the United States, FDA has specifically noted that probiotics are not defined as a regulatory product category under the Federal Food, Drug, and Cosmetic Act or Public Health Service Act. Products described as probiotics may instead fall under food, dietary supplement, drug, or biological product frameworks depending on factors such as intended use.
The same general principle applies to postbiotics.
“Postbiotic” remains primarily a scientific and commercial descriptor rather than a harmonized regulatory category. Depending on the jurisdiction, composition, format, intended use, and claims, a postbiotic preparation may be evaluated under existing frameworks for foods, food ingredients, dietary supplements, Natural Health Products (NHPs), novel ingredients, or therapeutic products.
In Canada, manufacturers may need to assess whether a microbiome-focused product falls within the food, NHP, or drug framework.
In the United States, the first question for a dietary-supplement application is whether the postbiotic preparation qualifies as a “dietary ingredient” under section 201(ff)(1) of the FD&C Act. Only after that threshold is met does the analysis turn to whether it is a new dietary ingredient and whether an NDIN or an applicable exemption is required. For use in conventional food, the intended use must be authorized as a food additive, be GRAS under the intended conditions of use or otherwise fall outside the food-additive definition. The important point is that replacing a viable microorganism with an inactivated preparation does not automatically resolve classification questions.
The regulatory strategy must still be developed around the actual preparation, intended population, conditions of use, and claims.
As neither Canada nor the United States have established a single postbiotic-specific regulatory framework, the characterization, inactivation and comparability considerations discussed below should be understood as science-based development and substantiation expectations unless they are imposed through the applicable food, dietary supplement, NHP or drug framework.
For probiotics, viability is part of the fundamental product concept.
FDA’s 2018 draft guidance concerning dietary supplements containing live microbial ingredients recognizes CFUs as a useful description of viable microbial quantity. However, the guidance remains in draft form and describes an intended enforcement-discretion policy rather than a finalized or binding requirement.
FDA explains that the weight of a microbial ingredient represents its total cellular mass, which can include both live and dead microorganisms, and therefore does not necessarily correlate with the number of viable microorganisms present. CFUs measure culturable microbial units capable of replicating under the specified test conditions and forming colonies. They do not measure total microbial biomass or postbiotic biological activity.
This creates a distinct development challenge for probiotics.
Manufacturers must consider whether the intended number of viable microorganisms can be maintained through:
For U.S. dietary supplement labelling, FDA’s draft policy contemplates declaring CFUs within the Supplement Facts panel in addition to—not instead of—the quantitative amount by weight required under 21 CFR 101.36, provided the specified conditions are met. The draft policy applies only to dietary supplements containing live microbial ingredients and does not apply to postbiotics or conventional foods.
Postbiotics largely reverse this problem.
In Canada, probiotic NHP product-licence applications and proposed labels must declare viable microorganism quantities in CFU; quantities expressed only by weight or volume are insufficient. The declared viable quantity is expected to be available through the product’s shelf life. For foods, Health Canada treats “probiotic” and similar representations as communicating a health benefit and has established accepted claims and conditions for specified live microorganisms. These probiotic requirements and accepted claims should not automatically be applied to an inactivated postbiotic preparation.
The objective is no longer to preserve viability. Instead, manufacturers must demonstrate that microorganisms have been appropriately inactivated while maintaining control over the characteristics of the preparation that are relevant to its safety, quality, and intended biological activity.
This can create advantages in formulation stability and distribution, but also introduces a different set of analytical and manufacturing questions.
With probiotics, manufacturing controls must protect the characteristics of a living ingredient.
Processing temperature, moisture, oxygen exposure, formulation matrix, packaging, and storage conditions can all influence survival.
With postbiotics, the inactivation process itself becomes an important part of product identity.
Heat, pressure, irradiation, and other processing methods can produce different structural and compositional changes even when manufacturers begin with the same microorganism.
This means two preparations derived from the same microbial strain may not necessarily be scientifically equivalent.
For postbiotics, manufacturers may therefore need to establish controls around:
Source organism characterization. The microorganism from which the preparation originates should be adequately identified and characterized.
Inactivation. The manufacturing process should consistently achieve the intended level of inactivation.
Confirmation of inactivation and residual viability. Fit-for-purpose methods should confirm that deliberate inactivation has occurred and quantify or control any residual viable progenitor microorganisms against a justified specification. A postbiotic does not necessarily have to be microbiologically sterile, and no universal residual-live-cell limit has been established. The appropriate acceptance criterion will depend on the preparation, intended use, population and applicable regulatory framework.
Composition. Relevant cellular components and retained fermentation products should be characterized where they contribute to product identity or biological activity.
Batch consistency. Manufacturers need to demonstrate that commercial batches remain sufficiently comparable to the material supported by the scientific evidence.
These considerations make the manufacturing process particularly important when determining whether existing postbiotic evidence can be applied to a commercial formulation.
One of the most established principles in probiotic science is that health effects can be strain-specific.
Evidence supporting one strain should not automatically be generalized to another strain within the same species. Historical international guidance has consequently emphasized microorganism identification, characterization, safety evaluation, and human evidence when substantiating probiotic health benefits.
For postbiotics, the evidence question can become even more specific.
Manufacturers must consider not only:
but also:
The result is an important distinction:
Probiotic evidence is often strain-specific. Postbiotic evidence may be both strain- and preparation-specific.
Changing an inactivation process or materially altering downstream manufacturing could therefore affect whether an existing clinical study remains applicable to the finished product.
Probiotic and postbiotic clinical trials share several fundamental principles.
For both categories:
The difference lies partly in how the investigational product itself is defined.
For a probiotic, investigators need to know that the strain and viable dose administered in the trial appropriately represent the commercial product.
For a postbiotic, comparability extends beyond strain identity.
The clinical test material should also represent the commercial product’s inactivation process, composition, processing conditions, and dose.
A clinical trial conducted using a heat-inactivated preparation, for example, may not necessarily substantiate a product created using a materially different inactivation process without adequate scientific justification.
This makes chemistry, manufacturing, and controls closely connected to clinical substantiation.
Both probiotics and postbiotics can generate interesting changes in biomarkers and microbiome composition.
Those findings do not necessarily translate into commercially usable health claims.
A study might demonstrate changes in:
These findings can help explain biological plausibility, but manufacturers should distinguish between demonstrating biological activity and demonstrating a meaningful health benefit.
The intended commercial claim should therefore influence clinical development from the beginning.
If the intended positioning relates to digestive function, immune health, or another physiological outcome, the study should include endpoints capable of substantiating that positioning rather than relying exclusively on exploratory microbiome measurements.
This principle applies to both probiotics and postbiotics, but it becomes especially important for emerging postbiotic preparations where mechanistic research may be more developed than human clinical evidence.
One potential advantage of postbiotics is that they do not contain intentionally viable microorganisms.
This may reduce certain concerns associated with microbial replication, translocation, or infection.
The distinction is clinically relevant because live microbial products can require additional caution in vulnerable populations.
Published literature has documented rare but serious complications associated with probiotic administration in certain high-risk patients. A review of Saccharomyces boulardii, for example, identified particular concerns in critically ill or immunocompromised individuals and those with central venous catheters. Importantly, those findings should not automatically be generalized to all probiotic strains or products.
More recent regulatory actions have reinforced the importance of population-specific risk assessment when live microorganisms are used in vulnerable populations.
However, the absence of viable microorganisms should not be interpreted as proof that a postbiotic is inherently safe.
Postbiotic safety must still be evaluated based on the specific preparation, composition, dose, route of administration, intended population, and conditions of use.
Inactivation changes the risk profile. It does not eliminate the need for a safety assessment.
| Consideration | Probiotics | Postbiotics |
| Microbial state | Live microorganisms | Inactivated microorganisms and/or their components |
| Primary characterization focus | Strain identity and viability | Source organism, inactivation process and final preparation |
| Quantification | Viable count, commonly expressed as CFUs | Preparation-specific measures of bio-mass; CFUs may be useful for controlling residual culturable organisms but is not a surrogate for total postbiotic dose or biological activity. |
| Shelf-life concern | Maintaining required viability | Maintaining composition, stability and relevant biological characteristics |
| Manufacturing focus | Protecting microorganism viability | Controlling and validating inactivation and preparation consistency |
| Evidence specificity | Frequently strain-specific | Potentially strain-, process-, and preparation-specific |
| Clinical comparability | Same strain, viable dose and relevant formulation | Comparable progenitor microorganism(s), cultivation and matrix, inactivation and downstream processing, composition, dose and final formulation. Material process changes require a scientifically justified comparability bridge. |
| Live-microbe safety considerations | May be relevant, particularly in vulnerable populations | Certain viability-related concerns may be reduced, but preparation-specific safety still requires evaluation |
| Regulatory category | Depends on jurisdiction, format, intended use and claims | Depends on jurisdiction, format, intended use and claims |
| Claims | Must reflect evidence for the relevant strain/product | Must reflect evidence for the specific postbiotic preparation |
This is likely to become one of the most important questions for manufacturers entering the postbiotic category.
In general, evidence demonstrating a health benefit from a live microorganism should not automatically be assumed to demonstrate the same benefit after that microorganism has been inactivated.
The biological activity responsible for the probiotic’s effect may depend on:
Inactivation could preserve some of these characteristics while eliminating or altering others.
Consequently, manufacturers considering an inactivated version of an established probiotic should conduct a comparability and evidence-gap assessment before relying on existing studies.
Where the available evidence does not adequately represent the commercial preparation, additional analytical, and mechanistic studies may help characterize the differences and support a comparability assessment. However, these data do not by themselves demonstrate the health benefit required under the ISAPP definition. If no controlled human study adequately represents the commercial preparation, intended population and proposed claim, postbiotic-specific human clinical evidence will generally be required.
The distinction between probiotics and postbiotics should be addressed before claims, formulation, and clinical programs are finalized.
For a probiotic, manufacturers should establish the intended strain, viable dose, shelf-life specifications, target population, and claims early enough to ensure the clinical and regulatory strategies remain aligned.
For a postbiotic, additional questions should be addressed:
What exactly is the preparation?
The term “postbiotic” alone does not sufficiently characterize the ingredient.
How is it manufactured?
Inactivation and downstream processing may affect the resulting preparation and its biological properties.
What evidence supports it?
Evidence for the source strain—or for the live probiotic—may not necessarily support the inactivated commercial preparation.
Is the clinical material representative?
The product tested in supporting studies should be sufficiently comparable to the product ultimately placed on the market.
What claim is being pursued?
Clinical endpoints, evidence requirements, and potentially product classification can all change depending on the intended claim.
Addressing these questions during development can prevent a common problem: creating a commercially attractive formulation first and attempting to build a regulatory and clinical justification around it afterward.
Postbiotics are unlikely to replace probiotics.
Instead, the two categories offer different approaches to microbiome-focused product development.
Live probiotics may be appropriate where the intended effect depends on microbial viability or metabolic activity. Postbiotics may offer advantages where manufacturers are seeking greater formulation flexibility, reduced viability-related stability constraints, or biological effects associated with inactivated cells and their components.
The key is matching the product format to the science.
As regulatory expectations around microbiome products continue to develop, manufacturers should expect increasing scrutiny of product identity, manufacturing reproducibility, clinically meaningful outcomes, and the relationship between the preparation that was studied and the preparation being marketed.
For both probiotics and postbiotics, strong product development begins with the same fundamental principle:
The evidence must support the product that consumers will actually use.
At dicentra, we support organizations developing probiotics, postbiotics, prebiotics, synbiotics, and other microbiome-focused products across food, dietary supplement, Natural Health Product, and clinical development pathways.
Our team can support manufacturers with:
The transition from a live probiotic to an inactivated postbiotic can create important formulation and commercialization opportunities, but it also changes the evidence and regulatory questions that manufacturers need to answer.
Early alignment between the product, manufacturing process, intended claims, and clinical evidence can help create a more defensible regulatory strategy and reduce challenges later in development.
Contact dicentra to discuss probiotic and postbiotic regulatory strategy, clinical development, claims substantiation, and market access.