Prebiotic vs probiotic soda: a field guide to the fizzy words

Walk down the soft drinks aisle in New York or London today and the cans are talking science. Prebiotic. Probiotic. Postbiotic. Live cultures. Fermented. The words come from laboratories, and each one means something precise there. On a shelf they blur together. Here is a field guide: what each kind of drink is, how to spot it, and what its word is allowed to say.

The words, as scientists use them

The definitions that scientists, companies and regulators around the world refer to come from the International Scientific Association for Probiotics and Prebiotics (ISAPP), whose expert panels published them, one by one, in the journal Nature Reviews Gastroenterology & Hepatology.

Look at how the definitions end. A probiotic, a prebiotic, a synbiotic and a postbiotic are each defined by a health benefit that has been shown. Fermented food is the odd one out: it is defined by how it is made, not by what it does. That one difference explains most of the confusion on the shelf.

The field guide

Classic soda. Carbonated water, sugar or a sweetener, flavour, sometimes caffeine. How to spot it: the oldest shelf in the shop. What it claims: refreshment, and nothing more scientific.

Prebiotic soda. A fizzy drink with soluble fibre added, usually a few grams a can, and usually less sugar than a classic soda. How to spot it: fibre in grams on the nutrition label, and a fibre among the ingredients. Nearly two-thirds of the American ones studied in 2026 were also sweetened at least partly with a non-sugar sweetener such as stevia.

Probiotic soda. A fizzy drink with live microorganisms added to it. How to spot it: the name of a bacterium or culture in the ingredients. By the scientific definition the word fits only if those microorganisms, in the amount the drink holds, have been shown to benefit health.

Kombucha and other fermented drinks. Sweetened tea, or another base, fermented by bacteria and yeasts, which makes it tart and naturally fizzy. How to spot it: "fermented" or "raw" on the label, a tangy taste, sometimes a cloudy sediment. A fermented drink is not automatically a probiotic one: that would need a benefit shown for what it contains. And fermentation makes a little alcohol. In the United States a kombucha that reaches 0.5 per cent alcohol at any point, even by fermenting further in the bottle, falls under the federal alcohol rules.

Postbiotic drinks. The newest of the words, agreed in 2021: microorganisms, or parts of them, that are no longer alive. How to spot it: the word itself, on the label.

Why the words are loaded

Because the scientific definitions build in a health benefit, regulators read the words as promises. In the European Union the position is set out in the guidance that member states agreed for the claims law of 2006, and the European Commission repeated it to the European Ombudsman in a case brought by a probiotics trade association: "contains probiotics" or "contains prebiotics" implies a health benefit, and so does "with prebiotic fibres". Each is therefore a health claim, and a health claim needs approval.

None has been approved. Since 2008 the European Food Safety Authority has assessed more than 300 claims on live microorganisms and on the words probiotic and prebiotic, and none received a favourable opinion. So, in the Commission's words, no health claim on probiotic or prebiotic is authorised for use on food in the EU. The United Kingdom kept the same law after leaving the EU, and its advertising regulator has ruled against an unauthorised prebiotic claim.

300+

claims on probiotics and prebiotics assessed in the EU since 2008

0

authorised for use on food in the EU

2–9 g

fibre a can, across 108 US prebiotic sodas

The United States works differently. There, "prebiotic" is not tied to any amount of fibre, as the researchers who studied 108 American prebiotic sodas pointed out when they presented their work to the American Society for Nutrition in July 2026. On average those drinks held about 35 kcal, 5 g of sugar and 5 g of fibre in a 355 ml can, and the fibre ranged from about 2 g to 9 g.

What the US does regulate is the word fibre itself. On an American nutrition label, dietary fibre means fibre that is naturally intact in plants, or an isolated or synthetic one that the Food and Drug Administration has accepted as having a beneficial effect. Inulin and inulin-type fructans are among the eight fibres the FDA said in 2018 that it would propose adding to that list, and allows on the label in the meantime.

What the label tells you that the name doesn't

• Fibre, in grams, and the size of the bottle it is counted in. A figure per can means little until you know whether the can is 220 ml or 355 ml.
• Sugar, in grams, per bottle and per 100 ml. A drink can be high in fibre and still sweet with sugar, or with juice.
• The ingredients. Which fibre, which sweetener, and, for a probiotic, which microorganism.
• For anything fermented: whether it is pasteurised, and how it should be kept.

Where Goli Pop sits

Goli Pop is a prebiotic soda by the trade's meaning of the word: a carbonated soft drink with added fibre, not a fermented or a probiotic drink. Each 220 ml glass bottle holds 6 g of added fibre, its label says low sugar, and it is sweetened with monk fruit / stevia. On its pages for the United Kingdom and France, where the word prebiotic counts as a health claim, it is described simply as a marble soda with 6 g of added fibre, and no health promise is made anywhere.