Poppi, the prebiotic soda that is loved by celebrities, will hit shelves in the UK on Thursday - but experts warn that the 'gut-healthy' soda may lead to digestive issues and cancer.

The soda, which is marketed as a healthier alternative to traditional fizzy drinks, has racked up a huge following of loyal supporters in the States, with fans including influencer Alix Earle, Paris Hilton, and Victoria's Secret Angel Elsa Hosk.

Following its impressive successes in America, the brand will launch five of its flavours at UK Tesco and Pret a Manger stores, before rolling out further in more shops.

The website explains: 'We all know soda is delicious. It's undeniable. But most sodas are loaded with empty calories and excess sugar, so we decided to make a better one.

'Poppi's a modern soda that combines 5g sugar, ingredients you can love and prebiotics to give you all the soda feels without the baggage.'

The drink contains no more than 35 calories each and includes natural sugar substitutes like Stevia.

They also contain inulin, a type of prebiotic fibre that helps 'feed' healthy bacteria in the gut microbiome - the collection of good bacteria in the gut - by producing short-chain fatty acids.

Increased amounts of fatty acids have been shown to improve digestion by regulating bowel movements and preventing constipation.

However, emerging research suggests short-chain fatty acids linked to inulin may increase the risk of certain cancers in the liver or colon by increasing inflammation and promoting tumour growth. 

A Poppi spokesperson told the Daily Mail: 'Poppi stands by the safety of its ingredients. 

'Inulin is a widely used, plant-based fibre that has been studied for decades and has been approved for use in foods and beverages by both EU and UK regulatory authorities since 2015. The emerging research does not establish a causal link between consuming inulin in foods or beverages and cancer risk.'

Doctors are now warning against consuming inulin on a regular basis, though they have also cautioned that more research is required.

The warning comes after the prebiotic soda brand Poppi was hit with a $5million lawsuit over claims the company 'misled' consumers and that the fibre content was too low to provide any benefits.

The plaintiffs in the class action suit said that two grams is too little to benefit anyone, unless a person drinks about four cans daily. At that point, the 20 grams of sugar - the equivalent of three cookies - would offset any benefit from the prebiotic. 

The brand's former owner agreed to an $8.9million settlement last year. The company did not admit to any wrongdoing.

Andrew Gewirtz, a biomedical science professor at Georgia State University, told Axios: 'The occasional can is unlikely to cause major harm. It's regular consumption that I'm not convinced is safe.'

Inulin is a form of dietary fibre found naturally in some plants, such as chicory root, garlic, onions, and Jerusalem artichoke. It is also considered a fructan, a type of prebiotic, meaning it can help feed 'good' bacteria in the gut.

Gut bacteria convert inulin and other prebiotics into short-chain fatty acids, which can help strengthen the gut's protective lining and reduce inflammation.

Poppi is one of the most popular prebiotic soda brands in America, generating about $500million in sales in 2024.

One can of Poppi contains three grams of dietary fibre, while Olipop can have up to nine grams, depending on the flavour. 

While inulin has been touted for its digestive benefits, Gewirtz claimed: 'Consuming grams of inulin regularly in supplements, beverages and inulin enriched foods may increase risk of cancer, potentially by dampening anti-tumour immunity.'

Gewirtz and a team from the University of Toledo published a study in 2018 looking at the effects of 'highly refined' fibres like inulin on mice. 

Several of the mice who had inulin added to their diets developed jaundice, a sign of liver failure. After six months, they developed liver cancer. 

A 2024 case study authored by the same team suggested that inulin 'may be carcinogenic'. 

The man in the case study had his first colonoscopy to screen for colon cancer at age 56, which came back normal. 

But seven years later, another routine cancer screening showed a malignant tumour at the start of his large intestine. The disease had also spread to his lymph nodes.

Now in his 60s, the man had no known colon cancer risk factors like obesity, alcohol use, or family history, and his diet was rich in organic, home-grown vegetables.

His only lifestyle change in the time between screenings was adding four grams of inulin powder daily to his diet. 

Researcher Dr Matam Vijay-Kumar of the University of Toledo said the patient contacted him after reading his previous research on inulin.

Dr Vijar-Kumar said last year: 'My first thought was how can he pinpoint that inulin caused colon cancer? It's incredibly difficult to identify a single cause of disease, particularly with cancer.

'However, after extensive communication with him about his medical history and lifestyle, combined with what we know from studies in mice, we were convinced that there was a plausible link.' 

Gewirtz suggested short-chain fatty acids may be responsible for this increased risk by triggering inflammation and increased cell production and division. This increases the risk of cancer cell production and tumours forming. 

However, he noted: 'Further studies are needed to help identify who might benefit from [inulin] and who should avoid it.' 

To boost healthy gut bacteria, he instead suggested increasing fibre intake through foods like artichokes, broccoli, lentils, seeds, oatmeal, brown rice, avocado, and raspberries. 

Poppi was founded in 2016 by husband-and-wife Allison and Stephen Ellsworth, after Allison longed to ditch soda, but not the taste, so she started mixing ingredients in her Texas kitchen.