The key difference is simple: a probiotic is a live microorganism shown to provide a health benefit under specific conditions, while a prebiotic is a substance selectively used by microorganisms in the body and associated with a health benefit.
They are not interchangeable: probiotics provide microorganisms, whereas prebiotics provide a substrate that certain microorganisms can use. Synbiotics combine these approaches, while postbiotics contain inanimate microorganisms and/or their components.
Prebiotic or probiotic: the difference at a glance
| Term | What it is | Examples | What to check |
|---|---|---|---|
| Probiotic | A live microorganism administered in an adequate amount, with a demonstrated health benefit | Products containing identified strains of bacteria or certain yeasts | Strain, dose, duration and the benefit studied |
| Prebiotic | A substance selectively used by host microorganisms, with a demonstrated health benefit | Certain fructo-oligosaccharides (FOS), galacto-oligosaccharides (GOS) and some fibres | Digestive tolerance and evidence for that specific substance |
| Synbiotic | A mixture of live microorganisms and one or more selectively used substrates | Formulations combining a documented strain with a prebiotic | Evidence for the final combination, not only each ingredient |
| Postbiotic | A preparation of inanimate microorganisms and/or their components, with a demonstrated health benefit | Inactivated microbial preparations | Composition, inactivation process and documented benefit |
Remember: not every fermented food is automatically probiotic, not every fibre is prebiotic, and combining the two does not automatically create a proven synbiotic.
What is a probiotic?
According to the international scientific consensus, a probiotic is a live microorganism that provides a health benefit when administered in an adequate amount. This definition involves several criteria: the microorganism must be accurately identified, remain alive in the product, be present at the studied dose and have shown a benefit in suitable research.
The word “probiotic” alone is therefore not enough to predict the effect of a supplement. Two strains belonging to the same species may have different properties. Results also depend on the dose, duration of use, population studied and intended outcome.
Where are probiotics found?
Some supplements and fermented foods may contain microorganisms that meet this definition. However, a fermented food is described as probiotic only when its microorganisms are identified, present in an adequate amount at the time of consumption and associated with a demonstrated benefit. Yoghurt containing live cultures is a familiar example, but this principle does not automatically apply to every fermented food.
What is a prebiotic?
A prebiotic is a substrate selectively used by microorganisms in the body that provides a health benefit. In the gut, prebiotics are often non-digestible carbohydrates that reach the colon, where certain bacteria can use them.
Fibres and compounds with potential prebiotic effects occur naturally in many plant foods, including garlic, onions, leeks, asparagus, artichokes, pulses, oats and slightly unripe bananas. However, a fibre is not automatically a prebiotic: its selective use and health benefit must be established.
Increasing certain fibres too quickly may cause gas, bloating or digestive discomfort. A gradual increase, together with adequate hydration, is generally easier to tolerate.
Probiotic or prebiotic: which should you choose?
There is no universal answer. The choice depends on your goal, diet, digestive tolerance and, in the case of a probiotic, the evidence available for the exact strain and product.
- To support a microbiome-friendly diet: a varied intake of plant foods and fibres is generally the foundation, provided it is well tolerated.
- For a specific goal: look for a probiotic whose strain, dose and duration have been studied for that goal, rather than choosing a high number of strains at random.
- If your digestion is sensitive: introduce fibre gradually. Some people tolerate certain prebiotics poorly, particularly when digestive symptoms are present.
- If symptoms persist or worsen: seek advice from a healthcare professional rather than adding more supplements.
Prebiotics and probiotics can be consumed together, but the combination is not automatically more effective. What matters is the quality of the evidence for the ingredients and, ideally, for the finished product.
What are synbiotics?
A synbiotic combines live microorganisms with one or more substrates selectively used by microorganisms in the body. The mixture must provide a demonstrated health benefit.
Experts distinguish between complementary synbiotics, in which each component has its own documented role, and synergistic synbiotics, in which the substrate is chosen to support the accompanying microorganism or microorganisms specifically. Simply putting a bacterium and a fibre in the same capsule does not always demonstrate a synbiotic effect.
What are postbiotics?
The scientific consensus published in 2021 defines a postbiotic as a preparation of inanimate microorganisms and/or their components that provides a health benefit. The microorganism does not therefore need to be alive at the time of use.
Postbiotics are not simply isolated metabolites such as short-chain fatty acids. The preparation must contain inactivated microbial cells or their components, with or without metabolites, and its benefit must be documented.
How to read a probiotic label
- Full identification: genus, species and, most importantly, strain.
- Quantity: the number of viable microorganisms guaranteed, ideally until the end of the product’s shelf life.
- Intended benefit: evidence for the strain and population relevant to your goal.
- Directions: dose, duration and storage conditions.
- Transparency: an identifiable manufacturer and access to supporting data or scientific references.
Can a gut microbiome test help?
A gut microbiome analysis can provide a snapshot of its composition at a particular time and help you understand this ecosystem more clearly. It does not diagnose a medical condition and cannot, on its own, determine whether you need a probiotic or prescribe a supplement.
The Nahibu kit enables you to collect a sample at home for gut microbiome analysis. It costs €199, and results are generally available 4 to 8 weeks after the laboratory receives your sample.
Frequently asked questions
What is the difference between a prebiotic and a probiotic?
A probiotic is a live microorganism associated with a demonstrated health benefit when used under the right conditions. A prebiotic is a substance selectively used by certain microorganisms in the body and associated with a health benefit. In short, one provides microorganisms while the other provides a substrate they can use.
Can you take probiotics and prebiotics together?
Yes. They can be combined, and such a product may be considered a synbiotic if it meets the scientific definition and provides a demonstrated benefit. However, the combination is not automatically better than either component used separately.
Which foods contain prebiotics?
Certain compounds found in garlic, onions, leeks, asparagus, artichokes, pulses, oats and slightly unripe bananas may have a prebiotic effect. Quantity, preparation and individual tolerance all matter. Not every dietary fibre meets the definition of a prebiotic.
Are all fermented foods probiotic?
No. Fermentation involves microorganisms, but they may no longer be alive in the finished product or may not have been studied for a health benefit. A fermented food may still be nutritionally useful without meeting the scientific definition of a probiotic.
How should you choose a probiotic?
Check the exact strain identity, guaranteed dose, recommended duration and studies relevant to your goal. The number of billions or strains shown on the packaging is not, on its own, a measure of product quality.
Can a microbiome test tell you which probiotic to take?
Not directly. A test describes certain aspects of your microbiome at a particular time, but it cannot by itself determine whether a probiotic is necessary or select a therapeutic strain. Results must always be interpreted in context.
Scientific sources
- Hill C. et al. Consensus statement on the scope and appropriate use of the term probiotic, Nature Reviews Gastroenterology & Hepatology, 2014.
- Gibson G.R. et al. Consensus statement on the definition and scope of prebiotics, Nature Reviews Gastroenterology & Hepatology, 2017.
- Swanson K.S. et al. Consensus statement on the definition and scope of synbiotics, Nature Reviews Gastroenterology & Hepatology, 2020.
- Salminen S. et al. Consensus statement on the definition and scope of postbiotics, Nature Reviews Gastroenterology & Hepatology, 2021.
Updated in September 2026. This article is for information only and is not a substitute for medical advice. Speak to a healthcare professional before using a supplement, particularly if you have a serious illness, are immunocompromised or pregnant, take medication, or have persistent symptoms.
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