What a Prebiotic Is, in Everyday Terms
Short answer. What is a prebiotic? It is a food ingredient, usually a type of fibre, that microbes can use as fuel, and it is not alive itself. A probiotic is the living microorganism, so the two words describe different things even when they appear on the same label.
- A prebiotic is fuel for microbes; a probiotic is the microbe.
- Inulin is a common prebiotic fibre found in plants and added to some products.
- Evidence for oral probiotics is still developing and mixed.
- Supplements do not replace brushing, cleaning between the teeth or dental checkups.
The short definition
A prebiotic is a substance that the microorganisms already living in your body can use as a food source. In practice that almost always means certain fibres or similar carbohydrates that your own digestion does not break down. The key point is that a prebiotic is not a living thing. It is closer to the fertiliser than the seed.
That is why the word is often confused with probiotic. The two differ by only a couple of letters but describe opposite sides of the same idea: one is the organism, the other is what it may eat.
How a prebiotic differs from a probiotic
Probiotics are live microorganisms. On a label they are named by genus, species and sometimes a strain code, for example Lactobacillus reuteri. Effects are strain-specific, so a result seen with one strain does not transfer to a different product that happens to share a genus name.
Prebiotics are simply ingredients, so they are described by type and amount rather than by strain. When a product contains both a live strain and a prebiotic fibre, the label is combining two separate things, and each needs to be read on its own terms.
- Probiotic: live, named by strain, strain-specific
- Prebiotic: not alive, a fibre or similar ingredient
- Both: listed separately on a careful label
Where inulin comes in
Inulin is the prebiotic you are most likely to meet on a label. It is a fibre found naturally in a number of plants and is also added to foods and supplements. Our companion guide on everyday foods that contain inulin goes through where it turns up in a normal diet.
Some people notice digestive discomfort when they take in more of it than they are used to, so it is worth knowing it is there. Another guide on this site covers going slowly with fibre.
What the seller says about ProDentim
As an example of a product that lists both, the seller describes ProDentim as an oral probiotic sold as a chewable. The seller's page names three probiotic strains: Lactobacillus paracasei, Bifidobacterium lactis BL-04 and Lactobacillus reuteri. It also lists inulin among other ingredients, with no amounts given.
These are the seller's statements, not verified results, and the seller's own disclaimer says the statements have not been evaluated by the FDA. The label on the bottle is the document to rely on.
Is a prebiotic enough on its own?
Research on the mouth microbiome and on oral probiotics is still developing, and the evidence is limited or mixed. That applies equally to the idea that feeding microbes with fibre changes anything in the mouth. Nothing here should be read as a promise about gums, teeth or breath.
The dependable basics are the ones dental organisations commonly advise: fluoride toothpaste twice a day, cleaning between the teeth once a day and regular dental visits. If you are pregnant, breastfeeding, take medicines, have a medical condition or allergies, ask a dentist, doctor or pharmacist before using any supplement.
Questions readers ask
Is a prebiotic the same as fibre?
Most prebiotics are fibres, but not every fibre is treated as a prebiotic. The term is used for ingredients that microbes can use as food.
Do I need both a probiotic and a prebiotic?
There is no single answer, and the evidence is mixed. A dentist, doctor or pharmacist can advise on whether a supplement makes sense for you.
Why does the label list inulin without an amount?
Some sellers list ingredients as a blend without quantities. If amounts matter to you, check the bottle label and ask the seller.
Who should check with a professional first?
Anyone pregnant or breastfeeding, giving something to a child, taking medicines, living with a medical condition or with allergies should ask first.
Talk to a professional. Persistent bleeding, pain, swelling, loose teeth or sores that do not heal need a dentist's attention, not a supplement.