Prebiotics vs Probiotics

What's the difference, and which do you actually need?

Gut health advice is everywhere right now, and so are the expensive products promising overnight miracles.

We sat down with our Gastroenterologist, Dr Alasdair Patrick, to cut through the noise on prebiotics and probiotics — what they actually do, and which one deserves a place in your routine.‎

What is our Gut Microbiome?

Our microbiome is the ecosystem of trillions of tiny organisms that live in our intestines. It is essentially a garden, made up of bacteria, fungi, and parasites— When the garden is flourishing, we flourish, but when it is out of balance, it can affect our energy, immunity, cognition, bowels, skin, mood, and even cause diseases.

Part of our microbiome is made up of probiotics (good bacteria) and prebiotics are the food source that feeds them. While they sound similar, probiotics and prebiotics are very different and have different roles in the gut.

Probiotics

Probiotics are the "good bacteria" — strains like Lactobacillus and Bifidobacterium that already live in your gut. Illness, ageing, certain medications, and a poor diet can all reduce their numbers and variety. Having enough probiotics and having a broad variety of strains is essential to overall health.

Here's the part most people don't realise: probiotics you take as a supplement don't move in permanently. They're transient — they pass through your system over 2–3 days, doing a specific job along the way.

Prebiotics?

Prebiotics are food that feed the beneficial bacteria (probiotics) that are already in your gut. They encourage good bacteria and discourage bad.

So, to continue the garden analogy, our gut microbiome is the garden, probiotics are the plants, and prebiotics are the fertiliser. Probiotics pass new bacteria through your system, and prebiotics nourish the beneficial bacteria already in your gut.

Should I take them as supplements?

Probiotic supplement?

Because your gut already produces its own bacteria, a probiotic supplement only helps if you're genuinely short on a specific strain — from illness, medication, or diet. A generic, untargeted probiotic is often money spent for little benefit. There are approximately 8,000 different strains of probiotic, so, if you think you might need to supplement a probiotic, search for the best strains for your specific symptoms.

Prebiotic supplement?

Yes, almost universally. Unlike probiotics, prebiotics don't need to be matched to a specific deficiency — they simply improve the environment your existing bacteria live in. They also support mineral absorption, bowel regularity, metabolism, and appetite control.

Additionally, a quality prebiotic can help prevent the spread of harmful bacteria by limiting the nutrients they need to thrive, therefore protecting your gut from their colonisation.

The right prebiotic (especially Partially Hydrolysed Guar Gum) can also help alleviate unpleasant gut symptoms like wind, bloating, cramps, constipation and diarrhoea.

Things to look for in a prebiotic

It should be a genuine prebiotic fibre, not just any fibre — not all fibres are prebiotics.
Many prebiotics are high in FODMAPs, so if you have gut issues, choose a prebiotic that is Monash Certified as low FODMAP.‎

The bottom line

Probiotics and prebiotics do different jobs. If you're unwell, on certain medications, or eating a limited diet, a targeted probiotic may help.

Prebiotics are the safer, broader bet: most of us (around 95%) don't get enough fibre day to day, which means our gut bacteria aren't getting the fuel they need.

Most people don't need a new garden. They just need better fertiliser.