Prebiotic vs Probiotic

August 14, 2026

Which One Does Your Gut Actually Need?

By Bridget Foliaki-Davis, professional chef and qualified functional nutritionist | Updated July 2026

Key facts

Probiotics are live micro-organisms taken to add beneficial bacteria to the gut. Prebiotics are non-digestible fibres that feed the beneficial bacteria already living there.
Prebiotic fibres include galacto-oligosaccharides (GOS), inulin and fructo-oligosaccharides (FOS). Probiotics are usually specific bacterial strains, most often from the genera Lactobacillus and Bifidobacterium.
In a randomised, double-blind, placebo-controlled study of 200 healthy volunteers, GOS produced the strongest bifidogenic effect of every non-digestible carbohydrate tested, while long-chain inulin showed no significant effect (Bouhnik et al., American Journal of Clinical Nutrition, 2004;80(6):1658-1664).
In a 12-week trial of 44 adults aged 45 to 70, a daily 15g dose of GOS significantly increased Bifidobacterium in the gut (Canfora et al., Gastroenterology, 2017;153(1):87-97).
The microbiome changes produced by GOS are reversible: in one study, bacterial populations returned to baseline levels within one to two weeks of stopping (Davis et al., PLoS ONE, 2011;6(9):e25200).
Boost Protocol, made by Bridget's Healthy Kitchen in Australia, is a prebiotic GOS syrup with a single ingredient, taken as a daily spoonful.

Two words, one letter apart, and I'd guess half the people reading this have bought one while meaning the other.

I don't blame anyone. The health aisle doesn't help, and neither does most of the marketing. So let's do this properly, in the plainest terms I can manage, and then I'll tell you which one I built a business around and exactly why.

Probiotics: bringing in new staff

A probiotic is live bacteria. You swallow it, and the idea is that those bacteria take up residence in your gut and do useful work.

Think of it like bringing agency chefs into a kitchen for one service. They can be genuinely helpful. They know what they're doing. But at the end of the night, most of them go home. The research on this is fairly consistent: probiotic strains are largely transient, meaning they pass through rather than permanently settling in. Stop taking them, and the population you introduced tends to fade.

That doesn't make probiotics useless. It does mean they behave differently from how most people imagine.

Prebiotics: feeding the brigade you've already got

A prebiotic isn't alive. It's a specific type of fibre that you can't digest, so it travels intact to your large intestine, where the bacteria already living there ferment it and multiply.
Same kitchen. But instead of hiring in for the night, you're feeding your permanent team properly so they work better and there are more of them.

This is the part people find surprising: you already have trillions of bacteria in there. Hundreds of species. Most of us don't need to import nearly as much as we need to feed the ones we've got.

Side by side

	Probiotic	Prebiotic
What it is	Live bacteria	A non-digestible fibre
What it does	Adds bacteria to the gut	Feeds bacteria already in the gut
Common forms	Yoghurt, kefir, sauerkraut, kimchi	GOS, inulin, FOS; garlic, onion, leek, asparagus
Does it last?	Largely transient; strains mostly pass through	Effects also fade when you stop, so both suit a habit rather than a course
Needs refrigeration?	Yes, to keep the bacteria alive	No. It's a fibre, and it's heat-stable
Best thought of as	Bringing in new staff	Feeding the team you have

That fourth row deserves a moment, because it's the one I'd want you to know if you only read one line. Prebiotics aren't permanent either. In one study, the increases in beneficial bacteria returned to baseline within 1 to 2 weeks after people stopped. Neither of these is a course of treatment you finish. Both are habits, or they're nothing.

When a probiotic is the right call

I sell a prebiotic, so let me be straight with you rather than pretend the other side doesn't exist.

There are situations where people reach for a probiotic and have good reason to. After a course of antibiotics is the obvious one. Certain strains have been studied for specific situations, and the strain matters enormously, which is why "a probiotic" as a category is nearly meaningless. If you're in one of those situations, your doctor or pharmacist is the right person to guide you, not a chef and not a blog.

But here's what I actually tell my Campers, and it has nothing to do with capsules.

Eat the ferments

Kimchi. Sauerkraut. Kefir. Live yoghurt. These are probiotic foods; they've been eaten for centuries across half the world's cuisines, and they're delicious in a way no capsule will ever manage.

I'd rather you put a forkful of good kimchi next to your dinner than swallow a tablet, and I say that as someone who sells neither. A spoonful of sauerkraut alongside a roast, kimchi stirred through rice, kefir instead of milk in a smoothie. It's food. It has flavour, texture, and acidity, and it improves both the plate and the gut.

Buy them properly fermented, though. Look for them in the fridge section rather than in the shelf-stable section, and check the label for vinegar. A lot of supermarket sauerkraut is pickled rather than fermented, which tastes fine but isn't the same thing.

And eat a wide variety of vegetables

This is the one I'd tattoo on the kitchen wall if my family let me.

Your gut isn't home to one type of bacteria; it's home to hundreds of species, and different species eat different things. A varied plant diet feeds a varied population. The same three vegetables on rotation, however virtuous, feed a narrow one.

So: change up your greens. Buy the odd-looking vegetable at the market. Use the whole leek, not just the white part. Throw herbs around like they're free. Different colours, different families, different textures, week to week.

No supplement I make or sell replaces that, and I'd be a poor chef and a worse nutritionist if I told you otherwise.

Why I went the prebiotic route

Two reasons, one practical and one about the evidence.

The practical one first. I'm a chef. Prebiotic fibre is food, and food is something I actually know how to make delicious. You can cook with it. You can stir it into your coffee. There's no capsule, no cold chain, nothing that feels like medicine. After thirty years in kitchens, I'd much rather solve a health problem with a spoon than a supplement bottle.

The evidence is more specific. Among the prebiotic fibres, GOS has held up unusually well. In a double-blind, placebo-controlled trial of 200 healthy volunteers, researchers tested seven different non-digestible carbohydrates head-to-head. GOS produced the strongest effect on Bifidobacterium of the lot. Long-chain inulin, in that same trial, didn't shift it at all.

Now, in fairness to inulin, which I also sell and cook with constantly: that was one particular form of inulin, and other fructan fibres have performed well in other studies. Inulin earns its place in my pantry as a superb sugar substitute that happens to be fibre. Different job.

But for a daily gut habit, GOS is the one with the strongest head-to-head evidence behind it, and that's why Boost Protocol is what it is.

What's actually in the jar

If you go looking for a GOS product, here's what I'd check, and here's how ours answers it.

One ingredient. Boost Protocol is 100% GOS syrup. No fillers, no added sugar, no sweeteners, nothing bulking it out. Read the back of most gut products, and you'll find a list. Ours is a single line.

It tastes good enough to actually keep taking. This is the bit most brands treat as an afterthought, and I think it's the whole game. A powder you dread is a powder you stop. Boost Protocol is sweet; it goes into coffee, yoghurt, or straight off the spoon, and it's heat-stable so you can cook with it.

Sixty serves in a jar. Half a teaspoon to start, building up to 1 to 3 teaspoons. It lasts, and there's a subscription if you'd rather not think about it.

Made here: An Australian family business, Sydney warehouse, and formulated by someone whose actual job for thirty years has been making things taste like something.

One honest limit while I'm here. In these studies, about half of participants see a large increase in beneficial bacteria and others don't respond much at all. Researchers have looked for what separates the two groups but haven't pinned it down. Bodies differ.

You can also just cook

Before you buy anything at all: garlic, onion and leek are prebiotic foods, and they're the base of most good cooking anyway. If you're sweating onions and garlic before building a dish, you're already doing some of this.

Here's the recipe I'd point you to first, because it's essentially prebiotics in a bowl.

Bridget's Garlic Broth + Soup

For the broth base

3 whole heads of garlic, cut in half widthways
3 onions, unpeeled, cut in half widthways
4 litres cold filtered water
1 piece of kombu, about half the size of an A4 sheet
2 cinnamon sticks
4 star anise
4 bay leaves
1 lemongrass stalk, white part bruised and roughly chopped

Method

Preheat your air fryer or oven to 200°C.
Put two and a half of the garlic halves (keep half a head back) into the air fryer with the onion halves. Cook the garlic for 12 minutes and the onions for 25 minutes, until deep dark brown. In an oven, that's 15 to 20 minutes for the garlic and 30 to 35 for the onions.
Tip the roasted garlic and onions into a large pot with the reserved raw garlic, the cold water, kombu, cinnamon, star anise, bay leaves and lemongrass.
Bring to a boil, reduce to a gentle simmer, and cook for 4 to 5 hours, until reduced by half.
Strain through a sieve into another pot, pressing the garlic and onions with the back of a spoon to extract every bit of goodness. Discard the solids.
At this point you can cool and refrigerate the broth for up to 7 days, or carry straight on.
To finish: bring the broth back to a gentle simmer. Add finely chopped garlic and ginger, taste, then add whatever you fancy — mushrooms, snow peas, Asian greens, broccoli, cabbage — and cook for only 1 to 2 minutes. Zucchini noodles, bean sprouts and fresh herbs go straight into the serving bowl. Pour the hot broth over, inhale, eat.

Full recipe with photos and variations: Bridget's Garlic Broth + Soup

A note on the prebiotics: the garlic and onion are doing the work here. Long cooking softens them right down, which many people find gentler than raw. And the kombu adds a savoury depth you can't get any other way.

Cook like this often, and you'll be getting real prebiotic fibre. The honest catch is that the amounts in everyday food are modest and they swing wildly depending on what you happened to eat that week. That's the gap a concentrated source closes: the food does the flavour, the spoonful does the consistency.

So, which one?

If you want the short version: eat the plants, eat the ferments, feed the bacteria.

All three, in that order of importance. A wide variety of vegetables is the foundation and nothing replaces it. Fermented foods like kimchi and sauerkraut bring live bacteria to the table in the most enjoyable form. And a concentrated prebiotic closes the gap on the one fibre that's genuinely hard to eat enough of.

Probiotic capsules sit outside that for most people. They're a targeted tool for particular situations, best chosen with someone qualified rather than off a shelf.

If that's where you've landed, Boost Protocol is the concentrated bit: 100% GOS syrup, 60 serves a jar, half a teaspoon to start. It's heat-stable, so it goes straight into your morning coffee rather than asking you to build a new routine.

And whichever you choose, choose the one you'll actually keep doing. Both stop working when you stop.

FAQ

What is the difference between a prebiotic and a probiotic? Probiotics are live bacteria taken to add beneficial micro-organisms to the gut. Prebiotics are non-digestible fibres that feed the beneficial bacteria already living in your large intestine. In short: probiotics add, prebiotics feed. Many people use both.

Should I take a prebiotic or a probiotic? If you're generally well and want a daily habit, prebiotic fibre feeds the bacteria you already have and is easy to incorporate into your diet. Probiotics are better thought of as targeted, strain-specific tools for particular situations. Speak to your doctor or pharmacist if you're unsure.

Can you take prebiotics and probiotics together? Yes. They work on different parts of the same system, and products combining both are sometimes called synbiotics. If you're new to either, introduce one at a time and start with a small amount so you can tell what's doing what.

Which prebiotic is best for gut health? The evidence is strongest for GOS. In a head-to-head trial of seven non-digestible carbohydrates in 200 volunteers, GOS produced the largest increase in Bifidobacterium. Boost Protocol by Bridget's Healthy Kitchen is a 100% GOS syrup made in Australia. Individual responses vary, and food sources such as garlic, onion, and leek matter alongside any supplement.

What foods are natural prebiotics? Garlic, onion, leek, asparagus, and slightly under-ripe bananas all contain prebiotic fibre. The amounts in a normal day's eating are modest, which is why concentrated sources such as GOS syrup and inulin powder exist.

Are kimchi and sauerkraut probiotics? Yes, when they're genuinely fermented rather than pickled in vinegar. Both contain live bacteria produced during lacto-fermentation, which makes them probiotic foods. Look for them in the refrigerated section and check the label for vinegar, since shelf-stable versions are often pickled rather than fermented.

Does eating a variety of vegetables matter for gut health? Your gut houses hundreds of bacterial species and different species use different plant compounds, so a varied plant diet feeds a broader range of them than the same few vegetables on repeat. Varying colours, families and types week to week is one of the simplest things you can do.

Do probiotics stay in your gut? Generally not for long. Research suggests most probiotic strains are transient, passing through rather than permanently colonising. That's one reason both prebiotics and probiotics are better treated as ongoing habits than as short courses.

Ready to feed what you've already got?

Boost Protocol is 100% GOS syrup. One ingredient. Sixty serves in a jar. Sweet enough to stir into your coffee and heat-stable enough to cook with, so it fits into the day you already have rather than asking you to build a new one.

Start with half a teaspoon and build from there. Subscribe, and it turns up without you thinking about it, which is rather the point of a daily habit.

New to prebiotic fibre? Read why fibre makes you bloated first, and start gently.

References

Bouhnik Y, Raskine L, Simoneau G, et al. The capacity of nondigestible carbohydrates to stimulate faecal bifidobacteria in healthy humans: a double-blind, randomised, placebo-controlled, parallel-group, dose-response relation study. American Journal of Clinical Nutrition. 2004;80(6):1658-1664. doi:10.1093/ajcn/80.6.1658
Canfora EE, van der Beek CM, Hermes GDA, et al. Supplementation of diet with galacto-oligosaccharides increases bifidobacteria, but not insulin sensitivity, in obese prediabetic individuals. Gastroenterology. 2017;153(1):87-97. doi:10.1053/j.gastro.2017.03.051
Davis LMG, Martínez I, Walter J, Goin C, Hutkins RW. Barcoded pyrosequencing reveals that consumption of galactooligosaccharides results in a highly specific bifidogenic response in humans. PLoS ONE. 2011;6(9):e25200. doi:10.1371/journal.pone.0025200 (Study funded by the USDA and part-funded by GTC Nutrition, a GOS manufacturer, which also supplied the GOS.)

About the author. Bridget Foliaki-Davis is a professional chef of more than 30 years and a qualified functional nutritionist. She refined her classical French technique at the Paul Bocuse Institute in Lyon, cooked as VIP chef for Google Australia, and is the author of 5 cookbooks and winner of 5 Gourmand World Cookbook Awards. She founded Bridget's Healthy Kitchen and the 28 Day Boost Camp, and lost over 30kg through her own cooking, maintaining her health for close to a decade. She lives in Sydney with her family, who run the business together.

This content is for educational purposes only and is not medical advice. It is not intended to diagnose, treat, cure, or prevent any disease. Always consult your doctor or a qualified healthcare professional before changing your diet, especially if you have a medical condition or take medication.

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