Kombucha used to be ‘just’ the fizzy, vinegary health drink you could find at farmers’ markets. But it’s really mainstream now.
The fermented tea – first brewed more than 2,000 years ago in China, where it is considered the ‘elixir of life’ and used to boost immunity and maintain the digestive system – is now widely available in pubs, coffee shops and on supermarket shelves.
Statistics show that Britain consumed 4.4 million liters of kombucha last year – an increase of over 800,000 liters on the previous year. Its success has been attributed to our increasing appetite for ‘functional health drinks’ that quench our thirst and provide health benefits, says Charlotte Foster, a specialist dietitian at Barts Health NHS Trust.
In the case of kombucha, these health benefits are believed to largely stem from the fermentation process the drink goes through.
This provides probiotics – beneficial bacteria – that are thought to help maintain the gut microbiome, the collection of microorganisms that live in the digestive tract and are important for everything from supporting our immune system to influencing our risk on obesity.
Kombucha – fermented tea first brewed in China over 2,000 years ago – is used to boost immunity and maintain the digestive system
Additionally, the tea element provides “antioxidants, which help with inflammation, and B vitamins that are essential for body functions such as the metabolism of dietary carbohydrates and proteins,” says Charlotte Foster.
“And it’s these potential benefits, along with the fact that they are generally low in calories and sugar, that people believe in when they buy them,” she adds.
But as more manufacturers jump on the bandwagon, consumers may not always buy what they think — because not all kombuchas are created equal.
Traditionally, only four ingredients were used to make kombucha, as Dr Amanda Lloyd, nutrition, health and diet researcher at Aberystwyth University, explains: ‘Black or green tea infused with hot water, sugar, tea- vinegar [also known as starter fluid, basically over-fermented kombucha that’s had most, if not all, of its sugar fermented away] and something called a SCOBY.
‘This stands for ‘symbiotic culture of bacteria and yeast’ and is a rather unattractive looking disc-shaped gelatinous blob. It is also called kombucha mushroom or kombucha mother.’
This mixture is then allowed to ferment for ten to twenty days.
Amanda Lloyd adds: ‘After this you can add further flavourings, such as mint or ginger, and then bottle it for another week or two to promote carbonation. Then that’s it: traditional kombucha full of live probiotics, polyphenols [powerful plant compounds with antioxidant effects] and antioxidants.
“Live cultures will continue to feed on the sugar and produce carbon dioxide, so you need to stop the process by keeping it chilled in the refrigerator,” she adds.
‘If you don’t do this, not only does it change the taste – it becomes increasingly sour – but the bottle can also become extremely fizzy. But that’s what kombucha is all about: it is alive and therefore somewhat temperamental.’
Now, however, some brands are making their drinks in a “more industrialized way,” says Lou Dillon, nutritionist and founder of Twisted Kombucha, a brand that makes kombucha in this traditional way.
‘This includes processes to extend shelf life by up to one year and make the product more stable, even under ambient conditions. Artificial sweeteners may also be used. This may give consumers a much wider choice – not everyone likes the sweet, yet vinegary taste of traditional kombucha – but the health benefits may not be the same.”
Statistics show that Britain consumed 4.4 million liters of kombucha last year – an increase of over 800,000 liters on the previous year
Evidence for kombucha’s health benefits is largely anecdotal – partly because such an unstable product is difficult to test – but a review of 15 studies in the journal Critical Reviews in Food Science And Nutrition last year concluded that there was some ‘evidence’ that kombucha- consumption benefits both the gut microbiome and obesity-related conditions.
But the studies that have been done relate to traditional ‘live’ kombucha.
Amanda Lloyd is currently running her own eight-week trial, involving 56 volunteers who will drink 330ml of ‘live’ kombucha daily for eight weeks – and blood, saliva and urine samples will be continually tested to look for changes in markers of stress and inflammation.
But a living drink, which is time-consuming to make and unstable when it comes out of the refrigerator, is not immediately suitable for mass production. That’s why some manufacturers have their kombucha pasteurized (which adds heat to kill bacteria that ‘spoil the product’) or microfiltrated (which filters out sediment and bacteria).
The problem with this, explains Dr Darshna Yagnik, senior lecturer and researcher in immunology at Middlesex University, is that ‘while pasteurisation is effective at removing most of the ‘bad’ bacteria in a product, it also removes the enormous amount’ friendly’ bacteria. ‘Bacteria too.’
It is these friendly probiotic bacteria that are the reason many people buy kombucha. To compensate for this deficiency, some manufacturers add their own probiotics. But Dr. Yagnik says these added bacteria won’t necessarily be as helpful.
“The live cultures from the fermentation would contain a mixture of different probiotic species, which can vary in amount in each batch produced,” she says.
‘However, any ‘added’ bacteria are usually limited to a specific strain. A variety of probiotics is much more beneficial because it contributes to a healthier immune system in the intestines, which supports better immune defense.’
Some brands ferment the product so long that no sugar remains, making it more stable again, but leaving the remaining bacteria with nothing to live on. Because it is vinegary in this state and not particularly tasty, manufacturers then add sweeteners such as stevia or erythritol.
‘Both stevia and erythritol are natural sweeteners – stevia is derived from a plant native to South America and erythritol occurs naturally in fruits and vegetables,’ says Charlotte Foster (@nutritionalevidence).
‘However, there is some evidence that stevia may have antimicrobial properties, meaning it could have a negative effect on the probiotic properties of kombucha itself.’ And she adds that erythritol “when consumed in large amounts, can cause adverse digestive symptoms such as diarrhea and bloating.”
Other kombuchas can be made with a concentrate or an “instant” mix – essentially a concentrated tea vinegar, diluted with tea blends and then flavored with artificial sweeteners with probiotic powder mixed in.
And according to Lou Dillon, a lack of labeling regulations means such products are difficult to spot. “Producers can get away with noting that a product contains live cultures, whether they occur naturally or are simply added after the manufacturing process,” she adds.
How can consumers avoid this minefield?
“If you want to make sure you’re buying a traditional kombucha, go to the refrigerated section first; you can’t store live kombucha at room temperature,” says Charlotte Foster. Then check the label.
‘Just looking at the wording doesn’t help, although the words ‘raw’, ‘pure’, ‘unpasteurized’ and ‘unfiltered’ are a good sign.
“My suggestion is to look at the back of the drink. If it states that the kombucha should be refrigerated rather than simply “chilled upon opening,” then that is a good indication that the kombucha is traditionally fermented.
‘It can also be helpful to see sediment at the bottom of the bottle or ‘floating’ bits in the drink – those are bits of the SCOBY and therefore the living culture, although that’s not always easy to see in a dark bottle .’
Lou Dillon also notes to look at the expiration date: live kombucha is only good for about five to eight months.
But the best way to ensure you get a pure, traditional kombucha is to make it yourself.
There are courses (in person and online) you can join where they will supply you with SCOBYs – or it’s easy to buy your own SCOBYs online (from around £10 for the individual SCOBY – up to £80 for a full kit including fermentation vessels and bottles).
“The process is not necessarily difficult, but you do need to be careful with kitchen hygiene and using sterilized containers,” says Dr. Yagnik. “If you don’t do this, mold or bad bacteria can grow and contaminate the kombucha, making you sick.”
‘A quick way to sterilize at home is to soak containers for five minutes in 10 percent household bleach or 70 percent isopropyl alcohol, which you can purchase online or at your local pharmacy.
‘Then rinse it with hot water before letting it dry completely in the sun; glass jars can also be dried in the oven at 140 degrees Celsius for ten minutes.
‘By doing it this way, you know for sure what goes into it. You can also make it to your own taste: you can make it as sweet as you want, add natural flavorings that you like and ferment it as much (or as little) as you want. It’s also much cheaper.’