Prebiotic fizzy drinks have landed in supermarkets with colourful cans, influencer enthusiasm and promises of a more microbiome friendly alternative to conventional soft drinks. Their appeal is simple: consumers get sweetness and fizz alongside a few grams of fibre marketed as support for gut health.

Yet the nutritional picture is not quite as bright as the packaging. An analysis of 108 prebiotic sodas found that the average can contained roughly equal amounts of sugar and fibre, with around 5g of each.

The research examined labels on products sold in the US. Although it has been presented at a nutrition conference, it has not yet appeared in a peer reviewed journal.

Products including Living Things Soda, Fibe Prebiotic Soda and XOXO Prebiotic Soda are designed to feed certain beneficial microbes already present in the gut. They commonly contain ingredients such as inulin, fructooligosaccharides, known as FOS, or galactooligosaccharides, known as GOS.

That makes them different from probiotics, which supply live bacteria. Prebiotics instead provide fuel for particular bacteria already living in the digestive system, but the potential benefit depends on the amount and variety of fibre provided.

Current UK guidelines recommend that adults consume 30g of fibre daily, while most people fail to reach that target. Registered dietitian, gut health researcher and Fibre Power author Dr Emily Leeming says 96% of Britons do not get enough fibre.

In that context, additional fibre can be useful, but Leeming says many drinks may not contain enough prebiotic fibre to produce a measurable effect. ‘The fibre added tends to be just one type of fibre too, unlike fibre-rich foods which contain a wide variety of different types of fibres for your health.’

Leeming also cautions that added fibre can give products a health halo even though they remain sweetened fizzy drinks. Her view is that consumers should treat them as something to enjoy occasionally rather than automatically regarding them as health foods.

Natasha Draycott, lead nutritionist at Rheal Superfoods, similarly says the value of a prebiotic drink depends on the particular product and what it replaces. ‘Most [prebiotic drinks] contain around 5g of prebiotic fibre, which can certainly contribute to your overall intake, but they shouldn't replace fibre-rich foods,’ says Draycott.

Sugar content may still compare favourably with some conventional options. The average prebiotic fizzy drink in the analysis contained around 5g of sugar, while a 330ml can of Coca‑Cola contains around 35g.

Almost two thirds of the products analysed also contained low or no calorie sweeteners such as stevia. However, having equal quantities of sugar and fibre does not mean that one cancels out the other or makes the drink essential for gut health.

‘For someone swapping a full-sugar fizzy drink for a prebiotic alternative, that’s likely to be a positive step,’ says Draycott. ‘But if you’re already drinking water or unsweetened sparkling water, I wouldn’t recommend adding a prebiotic drink purely for gut health.’

Increasing fibre can also bring uncomfortable effects, including bloating, wind and discomfort. Leeming says people with IBS may be particularly sensitive to ingredients such as inulin, although that does not mean everyone with IBS must avoid prebiotic drinks.

Draycott notes that inulin and chicory root fibre are high FODMAP ingredients that can trigger symptoms in some people with IBS. Carbonation may also cause bloating, so she advises people who are sensitive to added fibre to begin with a small serving and increase it gradually.

Prebiotic drinks can contribute to daily fibre intake and may offer a lower sugar replacement for regular fizzy lemonade, but experts still favour whole foods. ‘Think onions, asparagus, garlic, leeks, and beans – they are all great sources of different prebiotic fibres.’