Prebiotic vs Probiotic vs Postbiotic: What’s the Difference?

What Are Prebiotics, Probiotics and Postbiotics?

Before comparing them, let's understand what each term means.

Prebiotics: the selectively utilised substrate

A prebiotic is a substrate that is selectively utilised by microorganisms and provides a health benefit to the host.

In everyday language, you can think of prebiotics as certain substances that beneficial microorganisms can use.
Some dietary fibres and other compounds can have prebiotic properties, but not all fibre is automatically a prebiotic. Under the scientific definition, there needs to be evidence that the substrate is selectively utilised by microorganisms and that this is associated with a health benefit.

Probiotics: beneficial live microorganisms

A probiotic is a live microorganism that, when administered in adequate amounts, provides a health benefit to the host.
This definition is more specific than simply saying that a food contains "good bacteria."

For a microorganism to qualify scientifically as a probiotic, there needs to be evidence supporting its health benefit, along with appropriate identification, safety and an adequate amount being administered. The benefit can also be strain-specific, meaning that two microorganisms from the same species may not necessarily have the same effects.

Postbiotics: beneficial preparations containing inactivated microorganisms

A postbiotic is a preparation of inanimate microorganisms and/or their components that provides a health benefit to the host.
Unlike probiotics, the microorganisms in a postbiotic preparation are deliberately inactivated.

Importantly, postbiotic does not simply mean "dead probiotic." A product needs to meet the scientific criteria for a postbiotic and have evidence demonstrating a health benefit.

What Is the Gut Microbiome?

To understand the three "biotics," it helps to understand the gut microbiome.
Your digestive tract is home to a complex community of microorganisms, collectively referred to as the gut microbiota. These microorganisms interact with each other and with your body. The gut microbiome is the broader ecosystem and its genetic material, and researchers are continuing to investigate how these microorganisms interact with digestion, metabolism, immunity and other aspects of human health.

The relationship is not simply about having "more good bacteria." Your gut is an ecosystem containing many different microorganisms, and their composition and activity can vary considerably between individuals. This is one reason why a product that works for one person may not necessarily produce exactly the same result for someone else.

Prebiotics: Food for Your Microbial Community?

You may have heard the simplified phrase:
"Prebiotics are food for probiotics."
It's a useful starting point—but it's not quite scientifically complete.Prebiotics are not necessarily food specifically for probiotic supplements.

The scientific definition describes a prebiotic as a substrate that is selectively utilised by host microorganisms and provides a health benefit. These microorganisms can include members of the existing microbial community in your body. So a better way to think about prebiotics is:
Prebiotic → selectively utilised by certain microorganisms → contributes to a health benefit

What Foods Contain Prebiotic Components?

Some foods contain compounds that can have prebiotic properties. Examples commonly discussed in nutrition research include:

• Onions
• Garlic
• Leeks
• Chicory root
• Asparagus
• Bananas
• Whole grains
• Certain legumes

Some well-studied prebiotic compounds include inulin, fructooligosaccharides (FOS) and galactooligosaccharides (GOS).
However, it is important not to assume that every food containing fibre is automatically a "prebiotic food." Fibre and prebiotics are related, but they are not synonymous. The scientific definition of a prebiotic requires selective utilisation by microorganisms and evidence of a health benefit.

How to Get More Prebiotic Foods Into Your Diet

For most people, a varied diet is a sensible foundation for supporting overall gut health. You can incorporate a range of plant foods into meals, such as:

Breakfast: Oats + banana + nuts or seeds
Lunch: Whole grains + vegetables + legumes
Dinner: Garlic- and onion-containing dishes + vegetables + a protein source
Snacks: Fruit, nuts or other minimally processed foods

Rather than focusing on one "superfood," aim for variety. Different plant foods provide different types of fibres and other compounds that interact with the gut microbial community.

Probiotics: What Exactly Are They?

Probiotics are perhaps the most familiar of the three terms. You may have seen probiotics in:

• Supplements
• Yogurt
• Fermented dairy products
• Certain fermented foods
• Functional foods
• Powdered products
• Capsules

But here's an important distinction: Not every food containing live microorganisms is automatically a probiotic.
According to the International Scientific Association for Probiotics and Prebiotics (ISAPP), a true probiotic must contain specific live microorganisms that have been tested and shown to provide a health benefit at an appropriate dose. That means simply finding bacteria in a fermented food isn't enough to call the food a probiotic.

Why Does the Probiotic Strain Matter?

When choosing a probiotic, you may notice names containing a genus, species and strain designation. For example, you might see something structured like:
Genus → Species → Strain This level of identification matters because probiotic effects can be strain-specific.

Two microorganisms belonging to the same species can have different characteristics and different evidence supporting their use. So instead of asking only: "Does this product contain probiotics?" a better question is: "Which probiotic strain does it contain, at what amount, and what health benefit has been studied?" This is particularly important when evaluating probiotic supplements.

How to Choose a Probiotic

If you're considering a probiotic supplement, look beyond the word "probiotic" on the front of the packaging. Consider checking:

1. Which strain is included?
   Look for the full microbial identification where available.
2. What health benefit has been studied?
   Different strains may have different evidence.
3. What is the dose?
   A higher number isn't necessarily better. The appropriate amount depends on the microorganism and intended use.
4. How should it be stored?
   Some live microorganisms are sensitive to heat, moisture and oxygen.
5. Is the product suitable for you?
   People with certain medical conditions or significantly compromised immune systems should seek professional medical advice before taking probiotics.

Are Fermented Foods the Same as Probiotics?

No. This is one of the biggest misconceptions surrounding gut health.
Fermentation and probiotics are related concepts, but they are not synonymous.

A fermented food is produced through desired microbial growth and enzymatic conversion of food components.
However, for a food to be called a probiotic food, its live microorganisms need to meet the scientific criteria for probiotics—including evidence of a health benefit.
For example, the microorganisms involved in making a fermented food may not be present in the final product in a defined amount or may not have demonstrated a specific health benefit.
So: Fermented ≠ automatically probiotic.

Postbiotics: The Newer Term in Gut Health

Postbiotics have attracted increasing attention as scientists learn more about how microorganisms interact with the human body.
The concept is different from probiotics because the microorganisms in a postbiotic preparation are not alive.

The ISAPP definition describes a postbiotic as: a preparation of inanimate microorganisms and/or their components that confers a health benefit on the host.

Postbiotic preparations can contain:

• Inactivated whole microbial cells
• Microbial cell fragments
• Cell structures
• Other microbial components
• Metabolites or end products that may be present alongside the inactivated microbial material

Why Are Scientists Interested in Postbiotics?

One interesting question in microbiome research is: Do microorganisms always need to be alive to have an effect?
The answer appears to be more complicated than simply "yes."

Research suggests that some components of microorganisms can interact with human cells even when the microorganisms themselves are no longer alive.
This has led researchers to investigate how inactivated microorganisms and their components may interact with the body's epithelial and immune cells.

One potential practical advantage is that non-living preparations may have different stability and storage characteristics compared with live microorganisms. But this does not mean that all postbiotics are automatically better than probiotics.
As with probiotics, the specific preparation and evidence behind it matter.

Are Postbiotics Better Than Probiotics?

Not necessarily.
Postbiotics and probiotics work through different mechanisms and have different characteristics.
Probiotics are live microorganisms.
Postbiotics contain inactivated microorganisms and/or their components.

Because postbiotics don't require microorganisms to remain alive, they may offer different formulation and stability possibilities. But whether a postbiotic is useful depends on the specific preparation and the evidence supporting its health benefit.
Postbiotic research is still an evolving field.

Prebiotics, Probiotics and Postbiotics: How Do They Work Together?

Here's a simple way to visualise the relationship:

Prebiotic vs Probiotic vs Postbiotic: Which One Is Best?

This is probably the most common question. The answer is:
There isn't one universally "best" option.

Prebiotics, probiotics and postbiotics are different categories. The appropriate choice depends on factors such as:

• Your individual health needs
• Your diet
• The specific product
• The microbial strain or preparation
• The dose
• The evidence behind the product
• Your tolerance
• Any medical conditions or medications

The science behind the specific ingredient matters more than the label alone.

References

International Scientific Association for Probiotics and Prebiotics (ISAPP) — What is a probiotic?

ISAPP Consensus Statement — The definition and scope of prebiotics. Nature Reviews Gastroenterology & Hepatology.

ISAPP Consensus Statement — The definition and scope of postbiotics.

ISAPP — What is a postbiotic? Updated 2025.

ISAPP — Roundup of the consensus definitions: probiotics, prebiotics, synbiotics, postbiotics and fermented foods.

ISAPP Consensus Statement on Fermented Foods — Nature Reviews Gastroenterology & Hepatology.