Walk into almost any pharmacy, health store or supplement shop in South Africa and you are likely to see products promising better digestion, improved immunity, a healthier gut or a more balanced microbiome.

Some contain probiotics.

Others contain prebiotics.

And increasingly, you will see postbiotics appearing on product labels too.

The problem is that these three terms can sound interchangeable when they actually describe very different things.

A probiotic is a live microorganism that provides a demonstrated health benefit when consumed in an adequate amount.

A prebiotic is a substrate that is selectively used by beneficial microorganisms and provides a health benefit.

A postbiotic is a preparation containing inanimate microorganisms and/or their components that provides a health benefit.

Understanding these differences makes it much easier to evaluate products and avoid assuming that a higher number of bacteria, a longer ingredient list or a more expensive supplement automatically means a better product.

The most important question isn’t always “Which supplement should I buy?”

It is often:

“Do I actually need one?”

Probiotics: The Live Microorganisms

The term probiotic has a specific scientific meaning.

The International Scientific Association for Probiotics and Prebiotics (ISAPP) consensus definition describes probiotics as live microorganisms that, when administered in adequate amounts, confer a health benefit on the host.

That definition contains several important words.

“Live”

The microorganisms need to be alive when consumed.

This distinguishes probiotics from postbiotics, which contain inanimate microorganisms or their components.

“Adequate amounts”

Simply finding a bacterium in a product does not automatically make the product a probiotic.

The amount matters.

“Health benefit”

This may be the most overlooked part.

A microorganism isn’t a probiotic simply because it is a species that naturally occurs in the human gut.

There needs to be evidence that the particular microorganism, when consumed in a particular amount, provides a health benefit.

Why the Strain Matters

One of the biggest mistakes consumers make is assuming that all bacteria belonging to the same species will have the same effects.

They don’t necessarily.

For example, a product might contain Lactobacillus rhamnosus, but that does not tell you everything you need to know.

The specific strain may be identified by additional letters and numbers, such as Lactobacillus rhamnosus GG.

Different strains can behave differently and have different research behind them.

This is particularly important when probiotics are being considered for a specific condition.

A systematic review and meta-analysis of probiotics for irritable bowel syndrome found that effects differed between strains and outcomes, with some individual strains showing benefits for particular symptoms while the overall evidence remained heterogeneous.

So if a label simply says “10 billion probiotics”, that number alone tells you very little.

Is More CFU Always Better?

CFU stands for colony-forming units and is commonly used to describe the quantity of viable microorganisms in a probiotic product.

It is tempting to assume that:

10 billion = better than 1 billion.

But biology doesn’t work quite that simply.

The useful dose depends on the specific microorganism, strain, intended use and evidence behind the product.

A lower dose of a well-studied strain may be more relevant for a particular purpose than a much higher dose of an unrelated strain.

When comparing products, look beyond the large number printed on the front of the package.

Ask:

• What microorganism is included?
• What is the specific strain?
• What dose has actually been studied?
• What health benefit is supported by research?
• Is the product still within its expiry date?
• How should it be stored?

Those questions are much more informative than CFU count alone.

Prebiotics: Food for the Microbiome

Prebiotics are often confused with probiotics because the names sound similar.

But they are completely different.

A probiotic provides microorganisms.

A prebiotic provides a substrate that microorganisms can use.

The scientific consensus definition describes a prebiotic as a substrate that is selectively utilised by host microorganisms and provides a health benefit.

In simpler language, certain components of food can reach areas of the digestive tract where gut microorganisms can use them.

Many prebiotics are types of dietary fibre or related carbohydrates.

This is one reason that eating a varied, plant-rich diet is so important for gut health.

Where Do Prebiotics Come From?

Prebiotic compounds can occur naturally in foods such as:

• Onions
• Garlic
• Leeks
• Asparagus
• Legumes
• Oats
• Certain fruits
• Whole grains
• Some nuts and seeds

However, it is important not to label every fibre-rich food automatically as a “prebiotic”.

The scientific definition requires selective utilisation by microorganisms associated with a health benefit.

For everyday consumers, the bigger takeaway is simpler:

Eating a variety of plant foods gives your gut microbiome access to a variety of substrates.

This is one reason that fibre diversity matters.

Why Fibre Diversity Matters

Imagine eating exactly the same plant food every day.

You would still be getting fibre, but the types and structures of that fibre would be relatively limited.

Now imagine eating oats, beans, lentils, vegetables, fruit, nuts and seeds throughout the week.

You are providing a much broader range of plant-derived compounds to the gut microbial ecosystem.

This doesn’t mean that everyone needs to count different types of fibre.

It simply means that dietary variety is generally more useful than becoming obsessed with one particular “superfood”.

For a practical introduction to the relationship between food, fibre and gut bacteria, readers can also explore the Probiotics & Prebiotics Explained guide.

Postbiotics: The Newer Category

Postbiotics are where things become particularly confusing.

You may see the word on supplement packaging and assume that it simply means “the substances made by probiotics”.

That isn’t quite accurate.

In 2021, an international expert panel developed a consensus definition for postbiotics. They defined a postbiotic as a preparation of inanimate microorganisms and/or their components that confers a health benefit on the host.

That means postbiotics can include inactivated microorganisms or components of microorganisms.

They may contain metabolites, but metabolites alone do not automatically make something a postbiotic under this consensus definition.

This distinction matters because the word is increasingly being used in commercial marketing.

Why Are Postbiotics Interesting?

One potential advantage of postbiotic preparations is that they do not depend on the microorganisms remaining alive in the same way that traditional probiotics do.

That can create opportunities for products that are more stable under certain storage conditions.

However, “more stable” does not automatically mean “more effective”.

A postbiotic still needs evidence showing that the specific preparation provides a health benefit.

The postbiotic field is also considerably newer than the probiotic field, and researchers are still investigating which preparations work, for whom, at what dose and for which outcomes.

A scientific review discussing the development of postbiotics highlights the importance of distinguishing scientifically defined postbiotics from broad commercial claims.

Probiotic vs Prebiotic vs Postbiotic

A simple way to remember the difference is:

They are related concepts, but they are not interchangeable.

And there is another category you may encounter: synbiotics.

Synbiotics combine live microorganisms with substrates that are selectively utilised by microorganisms and provide a health benefit. Some are designed so the components work together, while others simply combine a probiotic and prebiotic.

Do You Actually Need a Supplement?

This is probably the most important question.

For many healthy people, the foundation of gut health should not be a cupboard full of supplements.

It should be a varied diet.

Vegetables.

Fruit.

Legumes.

Whole grains.

Nuts.

Seeds.

Adequate fluid.

Regular physical activity.

And a generally balanced eating pattern.

That does not mean supplements are useless.

There are circumstances where a particular probiotic, prebiotic or postbiotic may be appropriate.

The key is matching the product to the evidence and the individual situation.

When Might a Probiotic Be Considered?

Research has investigated probiotics for a range of conditions, including some forms of antibiotic-associated diarrhoea and IBS.

But results vary considerably depending on the strain and the outcome being measured.

For IBS in particular, systematic reviews have found evidence for benefits from some strains and formulations but not others.

This is why “probiotics are good for IBS” is too broad a statement.

A better question is:

Which strain, at what dose, for which symptom, in which population?

That’s how the scientific evidence is actually structured.

How to Read a Probiotic Label

The supplement aisle can be confusing, but you don’t need a science degree to ask useful questions.

1. Look for the strain

Species alone may not be enough.

Look for the full identification of the microorganism where available.

2. Check the CFU count

Look at the number of viable microorganisms, but don’t automatically choose the highest number.

The relevant dose depends on the particular strain and intended use.

3. Check the expiry date

Probiotic viability can change over time.

A product that contains live microorganisms needs to remain viable through its stated shelf life if that is part of its intended function.

4. Follow storage instructions

Some probiotic products require refrigeration, while others are formulated to remain stable at room temperature.

Always follow the manufacturer’s storage instructions.

This can be particularly relevant in South Africa, where products may experience substantial heat during transport or storage.

5. Look beyond the marketing claims

Be cautious with vague claims such as:

• “Detoxes your gut”
• “Balances everything”
• “Boosts immunity”
• “Repairs your microbiome”
• “Eliminates toxins”

A credible product should make it possible to understand what it contains and what evidence supports its intended use.

What About Fermented Foods?

Fermented foods are another part of this conversation.

Kefir, plain yoghurt, sauerkraut and certain other fermented foods can contain live microorganisms.

But fermented food and probiotic supplements are not automatically equivalent.

The microorganisms, quantities and food matrices can differ considerably.

The advantage of fermented foods is that they can be incorporated into an overall healthy diet alongside fibre-rich plant foods.

There is no need to choose between “food” and “microbiome”.

In many cases, the two work together.

Your diet provides substrates that influence the gut environment, while certain fermented foods can provide live microorganisms.

What South African Shoppers Should Look For

For consumers shopping for gut-health products, the most useful approach is to slow down before buying.

Instead of asking:

“Which product has the most bacteria?”

ask:

“What exactly is in this product, and what evidence supports its use?”

Look for:

• Specific microorganisms and strains
• Clearly stated amounts
• Expiry dates
• Appropriate storage instructions
• Transparent ingredient lists
• A clearly stated intended use
• Evidence that relates to the specific strain or preparation

And remember that price is not a scientific measure of effectiveness.

An expensive product is not automatically better than a cheaper one.

The Gut Health Foundation Comes First

It is easy to get caught up in the latest microbiome terminology.

Probiotic.

Prebiotic.

Postbiotic.

Synbiotic.

Psychobiotic.

The list continues to grow.

But the fundamentals remain important.

A varied diet rich in plant foods provides fibre and other compounds that interact with the gut microbiome.

Adequate hydration supports normal bowel function.

Regular movement supports overall health and digestion.

Adequate sleep and stress management also matter.

Supplements may have a role, but they should complement—not replace—the foundations of a healthy lifestyle.

The Gut Health SA resource library provides additional educational resources for readers who want to learn more about digestion, the microbiome, probiotics and prebiotics.

The Bottom Line

Probiotics, prebiotics and postbiotics are three different concepts.

Probiotics are live microorganisms with demonstrated health benefits.

Prebiotics are substrates selectively used by microorganisms that provide a health benefit.

Postbiotics are preparations containing inanimate microorganisms and/or their components that provide a health benefit.

None of these terms should automatically be treated as a synonym for “healthy”.

The evidence depends on the specific product, microorganism, preparation, dose, target population and health outcome.

For many people, the best place to start is not the supplement aisle.

It is the kitchen.

Build meals around a variety of plant foods. Eat enough fibre. Include fermented foods if you enjoy and tolerate them. Stay active and maintain healthy everyday habits.

Then, if you are considering a supplement for a particular digestive concern, look beyond the marketing and ask what the evidence actually says.

This article is for general educational purposes and does not replace personalised advice from a doctor, dietitian or registered healthcare professional. If you have a diagnosed gastrointestinal condition, are immunocompromised, are taking medication or are considering supplements for a specific medical problem, discuss your options with an appropriately qualified healthcare professional.