Explainer 2 min read

What is prebiotic fibre?

Prebiotic fibre is the part of plant food you don't digest. Your gut bacteria do. They ferment it, and produce the compounds your body actually needs.

Reviewed by our gut-microbiome scientists Built on 10+ years of MIT research

The short answer

Fibre that feeds your gut bacteria. Different fibres feed different microbes, so variety matters more than volume.

Most of us eat around 18g a day. The recommendation is 30g.
Prebiotic is not the same as probiotic. One is food, one is bacteria.
A blend of fibres does more than any single one.

How prebiotic fibre actually works

You have around 100 trillion bacteria in your large intestine. They can't eat what you eat until it reaches them, which is why fibre matters: it passes through the small intestine intact and arrives as food.

When your bacteria ferment that fibre, they produce short-chain fatty acids - mainly butyrate, propionate and acetate. Butyrate is the primary fuel for the cells lining your colon. Propionate helps regulate appetite and blood sugar. These compounds are the point. The fibre is just how you get them.

Here is the part most fibre advice misses. Bacteria are specialists. The species that ferment inulin are not the species that ferment beta-glucan or resistant starch. Eat one fibre and you feed a narrow group. Eat several and you support a broader, more resilient community.

Prebiotic or probiotic?

The two get used interchangeably. They are not the same thing. A probiotic adds new bacteria to your gut from outside. A prebiotic feeds the bacteria you already have.

Probiotics have to survive stomach acid, then compete with a community that's already established, which is a hard ask: most of their benefit stops once you stop taking them. Prebiotic fibre works with what's already there instead of trying to add to it, which is why it tends to be the more dependable of the two. See our page on probiotics for the full comparison, or explore our fibre blend to start feeding your own gut bacteria.

Prebiotic

Food for the bacteria you already have

Fibre. Survives digestion, arrives in the colon, gets fermented. Feeds a community that is already established.

Probiotic

New bacteria, added from outside

Live cultures. Most pass through without settling, so effects tend to stop when you stop taking them.

Both have their place. But feeding an existing community is generally more dependable than introducing a new one, which is where our work is focused.

Getting variety is the hard part

Knowing you need several different fibres is one thing. Eating enough of each, every day, alongside everything else you have to think about, is another.

Our blends combine multiple prebiotic fibres in the ratios our team arrived at through a decade of research at MIT. One spoonful, stirred into whatever you're already having.

Researched with

Common questions

Is prebiotic fibre the same as a fibre supplement?

Not necessarily. Many fibre supplements contain a single fibre, usually psyllium or inulin, aimed at regularity. A prebiotic blend is chosen for what your bacteria can ferment, which is a different goal.

How long before I notice anything?

Digestion often shifts within one to two weeks. The changes that depend on your microbiome adapting take longer, usually four to eight weeks of daily use.

Will it make me bloated?

Fermentation produces gas, so some people notice more wind in the first week. Starting with half a scoop and building up over a fortnight usually settles it.

Can I just eat more vegetables instead?

Yes, and you should. Food first is the right approach. The difficulty is variety and consistency: reaching 30g a day from several distinct fibre types takes planning that most days don't allow.

Does cooking destroy prebiotic fibre?

Mostly no. Fibre is heat-stable. Cooking and cooling some starchy foods, such as potatoes and rice, actually increases their resistant starch content.

Not sure which fibres you need?

Six questions about your digestion, energy and diet. We'll point you to the right blend.

Take the gut quiz Takes about a minute

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