What Are Prebiotics? A Food Scientist Explains

A simple guide to the fibres that feed your gut microbes.

What are prebiotics?

Prebiotics are one of the foundation pillars of gut health. After talking to lots of people at markets and through Supplamize, I've realised it's not always clear what prebiotics actually are or why they're so important.

Firstly, no, they're not the same as probiotics, even though the names sound very similar.

Probiotics are live microorganisms that, when consumed in adequate amounts, can provide a health benefit. Prebiotics aren't bacteria at all. They're specific types of carbohydrates that our digestive enzymes can't break down.

Because we can't digest them, prebiotics pass through the stomach and small intestine largely untouched until they reach the large intestine (colon). Here, they are selectively fermented by certain beneficial gut microbes.

That word selectively is important.

Different microbes prefer different types of prebiotic fibres. Some thrive on inulin, while others are better at fermenting fibres like apple pectin or partially hydrolysed guar gum (PHGG). By providing these fibres, we're helping support the growth and activity of beneficial microbes such as Bifidobacterium and Lactobacillus.

People often describe prebiotics as "food for the good bacteria", which is a helpful way to think about them, but I actually like another analogy.

Imagine your gut is a garden.

The beneficial microbes are the plants you want to grow. Prebiotics aren't just the food for those plants, they're actually more like the fertiliser that helps the whole garden flourish.

Why do prebiotics matter?

Your gut is home to trillions of microorganisms that help break down food and produce compounds that support the gut environment and influence many other parts of the body.

When beneficial gut microbes ferment prebiotic fibres, they produce compounds called short-chain fatty acids (SCFAs).

You may have heard this term before and wondered what it actually means.

The three main SCFAs are:

• Acetate
• Propionate
• Butyrate

These compounds play many important roles within the gut.

Butyrate, in particular, is the preferred fuel source for the cells lining the colon. It helps nourish the gut lining and supports a healthy gut environment.

SCFAs also help regulate the gut environment by lowering its pH. A slightly more acidic environment makes it harder for some less desirable bacteria to thrive while supporting many beneficial microbes.

Research also suggests this lower pH may improve the absorption of minerals such as calcium, magnesium and iron, showing that the effects of prebiotics extend well beyond digestion.

Perhaps even more interesting is that SCFAs don't just stay in the gut. Acetate, for example, is the most abundant SCFA found in the bloodstream and has been shown to cross the blood-brain barrier. Researchers are continuing to explore how SCFAs influence metabolism, immune function and communication between the gut and the rest of the body.

Your gut microbes work together

One of the most fascinating things about the gut microbiome is that the microbes don't work in isolation, they work together.

When one group of bacteria ferments a prebiotic fibre, it produces compounds that another group of bacteria can then use as its own food source. Scientists call this cross-feeding.

Rather than individual bacteria working alone, the gut functions as a complex ecosystem where microbes constantly interact with one another. It's one of the reasons why supporting a diverse gut microbiome is so important.

Not all fibre is a prebiotic

This is one of the biggest misconceptions.

While all prebiotics are dietary fibre, not all dietary fibre is a prebiotic.

To be considered a prebiotic, an ingredient needs to:

• Resist digestion in the small intestine.
• Be fermented by gut microbes.
• Selectively support beneficial microorganisms.

That's why you'll often see ingredients such as inulin, partially hydrolysed guar gum (PHGG) and apple pectin used in gut health products.

Not all prebiotic fibres behave the same way either. Some are fermented quickly, others more slowly, and different fibres support different groups of gut microbes. This is one of the reasons why eating a variety of plant foods, and including a variety of prebiotic fibres, may help support a more diverse gut microbiome.

Where are prebiotics found?

Prebiotics occur naturally in many fruits, vegetables, grains and legumes.

Some of the best-known sources include:

• Garlic
• Onion
• Leeks
• Asparagus
• Oats
• Legumes
• Slightly green bananas
• Chicory root

These are just a few examples. Prebiotic fibres are found in many different plant foods, which is one of the reasons eating a varied diet is so beneficial for gut health.

Researchers are also exploring prebiotic compounds from other sources, including milk, fungi and marine organisms, for use in future functional foods and health products.

Why can prebiotics sometimes make you feel bloated?

If you've ever increased your fibre intake and noticed more gas or bloating, you're not alone.

This is actually a normal part of the fermentation process.

As beneficial gut microbes ferment prebiotic fibres, they naturally produce gases alongside SCFAs. For many people, this settles as the gut adapts to the increased fibre intake.

If you're new to prebiotics, it's often a good idea to start with a smaller amount and gradually increase your intake over time.

If symptoms are severe, persist for an extended period or continue to worsen, it's important to speak with your healthcare professional, as there may be an underlying digestive condition or imbalance that requires further investigation.

Why we include prebiotic fibres in every Supplamize blend

Prebiotics form the foundation of every Supplamize blend because, in my opinion, it's difficult to build a healthy gut microbiome without first providing the microbes with the fuel they need.

Many Australians simply aren't eating enough fibre, or enough variety of fibre, to properly nourish their gut microbiome.

You can be eating what looks like a healthy diet, but if you're not regularly consuming a variety of prebiotic fibres, beneficial microbes may struggle to thrive and produce the SCFAs that help support a healthy gut environment.

That's why every Supplamize blend starts with carefully selected prebiotic fibres. Before we think about adding herbs, probiotics or other functional ingredients, we start by supporting the gut ecosystem itself.

Our Gut Health Blends contain:

• Chicory Root Inulin
• Partially Hydrolysed Guar Gum (PHGG)
• Apple Pectin

Our Skin Glow Blends contain:

• Chicory Root Inulin
• Partially Hydrolysed Guar Gum (PHGG)
• Agave Prebiotic Fibre

Each fibre has slightly different characteristics and is fermented differently by the gut microbiome. By combining multiple prebiotic fibres, we're aiming to create a stronger foundation to support a healthy and diverse gut ecosystem.

The bottom line

Prebiotics are much more than just "food for the good bacteria."

They help shape the gut microbiome by selectively nourishing beneficial microbes, supporting the production of important compounds like short-chain fatty acids, and creating an environment where those microbes can thrive.

Because in my opinion, if you don't build a strong foundation, everything else becomes much harder.

References

Al-Sheraji, S. H., Ismail, A., Manap, M. Y., Mustafa, S., Mohd Yusof, R., & Hassan, F. A. (2013). Prebiotics as functional foods: A review. Journal of Functional Foods, 5(4), 1542–1553. https://doi.org/10.1016/j.jff.2013.08.009

Monteiro, C. R. A. V., Bogea, E. G., Campos, C. D. L., Pereira-Filho, J. L., Almeida, V. S. S., Vale, A. A. M., Azevedo-Santos, A. P. S., & Monteiro-Neto, V. (2026). Prebiotics and gut health: Mechanisms, clinical evidence, and future directions. Nutrients, 18(3), 372. https://doi.org/10.3390/nu18030372