Kombucha Benefits and Risks: Experts Explain Toxins and the Habit That Can Undermine Gut Health

With its sharp, fizzy taste and image as a sophisticated swap for soda, kombucha has become an easy sell — especially when bottles advertise “beneficial bacteria” and support for a “healthy gut.”

The fermented tea drink has exploded in popularity in recent years, growing into a market with annual sales now exceeding $1.6 billion.

Fans say kombucha may help with everything from digestive discomfort to high blood sugar and cholesterol levels, while celebrities such as Selena Gomez and Lindsay Lohan have also given the beverage their backing.

But the question remains: does kombucha deserve its health halo?

Experts who spoke to the Daily Mail say shoppers should be careful, warning that the drink’s health claims may be overstated — and that some store-bought varieties contain more sugar than a Krispy Kreme donut.

They also note that levels of so-called gut-friendly bacteria can differ dramatically from one product to another, while some bottles may include ingredients many consumers are not expecting, including alcohol and caffeine.

“There are small studies looking at regular kombucha consumption showing health benefits and potential health improvements,” said Nebraska-based food scientist Dr Jennifer Auchtung. “But these were mostly carried out in animals.

“We don’t really have the good, large-scale human studies, that would be needed to show any potential health benefits, particularly for the gut.”

Kombucha has been around for at least 2,000 years, after first appearing in northeastern China, where it may have been used medicinally.

Homemade versions of the drink involve adding sugar and a starter culture of bacteria and yeast – known as a SCOBY, sometimes called the ‘mother’ – to black or green tea, then leaving the mixture to ferment, typically for around a week or longer.

The microbes feed on the sugar, producing acids, gases and other compounds that give kombucha its distinctive tart, slightly fizzy taste. The finished drink can also contain live microorganisms, which is why kombucha is often marketed as a probiotic.

However, grocery-store versions are normally pasteurized – or heated and cooled rapidly – to kill off any dangerous bacteria, before having healthy bacteria added. These may also be enhanced with extra sugar and fruit juice.

Health claims around kombucha largely focus on the billions of bacteria that can be produced during fermentation, which manufacturers suggest could improve the balance of microbes in the gut.

But experts say the presence of live bacteria does not automatically make something a probiotic. To earn that description scientifically, specific strains must be shown to survive in sufficient numbers and provide a proven health benefit.

In most commercial kombucha, the precise mixture and quantity of microbes varies considerably – and it remains unclear whether enough survive digestion to have any meaningful effect on the gut.

‘We know that many fermentation microbes don’t actually survive very well in your digestive tract,’ said Auchtung.

‘We do think having the dead bacteria present may boost the immune system or fuel beneficial microbes, so the number of bacteria in the drink could still be useful. But in terms of kombucha as a delivery vehicle for a probiotic, it’s really probably not the best that you could consume.’

More broadly, there has been surprisingly little research into kombucha’s health effects in humans.

A 2025 review by Brazilian researchers found only eight papers analyzing the health impacts of kombucha in people. Of these, only two studies showed it may help to ease gastrointestinal symptoms, such as constipation, while two also showed participants drinking kombucha had more healthy bacteria in the gut. 

The researchers concluded the results were ‘promising’ and suggested kombucha ‘may’ boost gut health, but said more studies were needed to confirm the findings. 

Some experts warn kombucha may actually make gut problems worse, particularly in people with irritable bowel syndrome.

That’s because it can contain certain sugars that aren’t fully absorbed during digestion. Instead, they are fermented by bacteria in the gut, producing gas that can trigger bloating and discomfort.

When choosing a kombucha at the grocery store, Auchtung said the first thing shoppers should check is the sugar content.

‘The biggest thing I would say to look for is the total sugars,’ she said. ‘If you were drinking this instead of a sugar-sweetened soda, then it would be a good substitute.’

She recommends choosing one with no more than ten grams of sugar per serving, to avoid turning what is marketed as a healthy alternative to soda into another significant source of added sugar. 

But some popular brands contain considerably more. 

A bottle of Health-Ade Kombucha, the brand endorsed by Lohan, can contain around 18 grams of sugar per 16-ounce bottle, which is roughly the same amount as two Krispy Kreme Original Glazed donuts. Synergy kombucha typically contains around 16 grams per bottle, while the KeVita brand contains around ten grams. The amount of sugar varies depending on the flavor.

Because it is made with tea, kombucha naturally contains caffeine, but this is in very small amounts – about five to 15 milligrams, or the equivalent of a decaffeinated coffee.

As it is made using fermentation, kombucha also contains alcohol but also in very small amounts.

‘For the average person, kombucha can be part of a healthy diet,’ said Auchtung.

‘There are modest health benefits and it definitely won’t do you any harm if consumed in moderation.’

Dietitian Tiffany Bruno added: ‘Kombucha can be a good choice for gut health, but it’s not a one-size-fits-all solution. 

‘It contains beneficial probiotics and polyphenols that support the gut. But bacteria in the gut need fiber.

‘It’s worth ensuring you are consuming enough, from a wide variety of foods, before adding things like kombucha.’

An estimated 95 percent of Americans fail to get enough fiber. Women are generally advised to consume around 25 grams a day and men around 38 grams.

For those who enjoy kombucha but want to avoid the sugar, Auchtung recommends unsweetened green tea, which still provides many of the beneficial compounds found in kombucha without the added sugar.

And for those specifically seeking a drink to boost digestive health, she recommends kefir, a fermented milk drink that contains live bacteria and has considerably more research behind its potential effects on the gut.