Kombucha is a fizzy, fermented tea linked to potential gut health benefits, but not all brands contain live microbes. Photo / 123rf
It’s one of the trendy gut health products populating our supermarkets – we ask the experts what’s in it and if it’s really good for you
Our appetite for fermented food and drink is showing no signs of being sated, with sourdough, kefir, kimchi, and now kombucha, staples on our shopping lists. But while the thought of drinking fermented tangy tea may not be to everyone’s taste, more of us are glugging the fizzy brew than ever in the hope of harnessing its supposed health benefits for the gut.
With popular brands priced at around $5 for a single-serve bottle, however, is the drink really worth it? Here, the experts share whether you should be drinking it and how to make your own.
“Kombucha is a slightly fizzy fermented tea that originated thousands of years ago in China,” says Dr Federica Amati, the head nutritionist at science and nutrition company Zoe and author of Every Body Should Know This.
It’s a fairly simple drink, made from four ingredients: black or green tea leaves, water, sugar and a “Scoby”, she says. The Scoby (which stands for symbiotic culture of bacteria and yeast) is a disc-shaped culture of various types of bacteria and yeast. The yeast converts the sugar into alcohol, which the bacteria then turns into different acids, making the drink more acidic and giving kombucha its characteristic tangy flavour.
“Some people also add flavourings like ginger, lavender or blueberry,” she says.
Kombucha is a probiotic, meaning it contains living bacteria, putting it in the same category as yoghurt, sauerkraut and sourdough bread.
“As with other fermented products, the live ‘good’ bacteria is thought to support the health of your gut microbiome, which can have positive effects throughout all of your body’s systems,” says Amati.
However, not all kombuchas will contain live microbes, as some brands pasteurise the drink, which kills off “bad” bacteria but also the “good” kind, says Sammie Gill, a registered dietitian and a British Dietetic Association (BDA) spokesperson. To decide which to go for, check on the packaging if the kombucha is unpasteurised (brands often state this) and another tell-tale sign is that the drink needs to be stored in the fridge, she says.
“Kombucha naturally contains a complex mixture of compounds including antioxidants called polyphenols, such as catechins,” says Gill. Catechins have been linked to a lower risk of inflammatory bowel disease.
The drink is also a source of vitamins (such as vitamins B and C), minerals (iron and zinc), and organic acids (such as acetic acid and glucuronic acid), she says.
“Kombucha has been linked with metabolic health including improved glycemic control in people with Type 2 diabetes,” says Gill.
This may be down to theaflavins, a group of antioxidant polyphenols, which are thought to improve blood sugar levels. Additionally, other compounds found in the drink may be at play, such as acetic acid, which is reported to have anti-diabetic properties.
“One of the main challenges with studying the health effects of kombucha is that each Scoby contains a slightly different mix of bacteria and yeast, and different bacteria and yeast have different health effects,” Gill says.
“To date, results from lab and animal studies suggest kombucha may have anti-obesity and anti-tumour effects, as well as cholesterol-lowering effects.”
However, she notes there is limited evidence in humans supporting these findings, so further studies are needed to confirm whether these effects occur in people. “Saying that, emerging studies show promise,” Gill says.
Alcohol is a natural by-product of the fermentation process used to make kombucha. Typically, shop-bought kombucha contains less than 0.5% alcohol by volume (ABV), though this can vary between brands, Gill says.
Therefore people with liver problems, sensitivity to alcohol and pregnant women should consult their doctor before trying it, Amati says.
If you’re making kombucha at home, the longer the fermentation, the higher the alcohol content, Gill says. Hard kombucha (the alcoholic version of normal kombucha) is intentionally fermented for longer to contain higher amounts of alcohol, typically 4-7% ABV, she says.
If drinking these, do so in moderation as with other alcohol drinks, she recommends. “At the same time, hard kombucha is a better option than cocktails containing lots of sugary syrups, fruit juices and sweeteners,” Gill says.
Shop-bought kombucha is likely to be safe to drink because manufacturers must follow strict food safety guidelines, says Amati. “However, if you prepare it at home, there is the potential that harmful bacteria and moulds may contaminate the drink.”
This is why it’s vital to follow hygiene practices to minimise the risk of contamination with potentially harmful bacteria, Gill says. “Use common sense and keep hands and work surfaces clean and sterile. Use appropriate vessels for fermentation, such as glass.”
“Some people have reported other side effects from drinking kombucha, such as nausea, vomiting and other gut symptoms,” Amati says.
These usually only occur among people who don’t normally drink kombucha and are mild and short-lived, Gill notes.
Gill says that “because kombucha is acidic, drinking too much kombucha on a regular basis can erode tooth enamel and increase the risk of tooth decay”.
As well as kombucha, other fermented drinks have become popular, including kefir (a fermented milk drink) and water kefir (fermented water).
“As with kombucha, the health effects of these drinks haven’t been studied in any depth, so we don’t know about specific health benefits,” says Amati.
“However, because they contain live ‘good’ bacteria, they are likely to support your gut health,” she says. “And they’re certainly better than standard fizzy drinks.”
When it comes to buying a kombucha, a good rule of thumb is to make sure you select one with few ingredients and that states on the packaging it contains “live cultures” or “live bacteria”, says Amati.
It’s also worth avoiding those that are high in sugar and contain lots of added ingredients, such as preservatives, artificial sweeteners or flavourings, Gill says.
Sugar is needed to make kombucha, as it acts as “food” for the Scoby and fuels fermentation, she explains. However, it’s always worth checking the label because the sugar content of kombucha can vary from 0g to around 4.5g per 100ml between brands, she says.
“Because kombucha has a distinctive sour flavour, some manufacturers choose to add other ingredients to increase palatability, such as artificial sweeteners.
“Making your own kombucha at home (see below) is a good approach because you can control exactly what goes in it.”
Recipe from Xanthe Clay
You’ll need your Scoby, a jar that holds at least 2.5 litres, four tea bags (or two tablespoons of loose leaf tea), 125g granulated sugar and a bottle of ready-made live, unflavoured kombucha (from your last batch, or if this is your first, buy a bottle of “live” unpasteurised kombucha). The ready-made stuff is there to make the initial liquid a bit sour, warding off unwanted bacteria until the Scoby/tea/sugar combo gets going and produces its own acidity.
You can purchase starter kits or cultures online or in health food stores (or from a friend who makes kombucha). Read independent customer reviews. Instructions should be simple with only a few ingredients required.
On the whole, yes. “Although we need to carry out more research into kombucha, it seems likely that it’s healthy,” says Amati. This is thanks to the live microbes it contains, which produce a wide range of bioactive compounds that might support health, along with the extra microbes that enter your gut, she explains.
It can be especially healthy, Gill says, if it’s drunk as an alternative to sugary or alcoholic drinks. Though if drinking it regularly, it is worth checking the label to ensure it’s not too high in sugar (less than 5g per serving will mean it is considered a healthier choice) or full of artificial sweeteners.
There are no hard and fast rules when it comes to how much kombucha we should drink, though, as with everything, moderation is key, says Gill.
The US Centre for Disease Control and Prevention suggests drinking no more than one large glass per day (around 300-350ml) for the general healthy population, she says.
If you enjoy the taste of kombucha, it’s perfectly fine to drink it daily, says Gill. Alternatively, “there are plenty of other drinks that contain health-promoting compounds including fruit teas, herbal teas, fruit infused water and milk”.
“Because kombucha contains small amounts of alcohol, it’s probably best to avoid it during pregnancy,” says Amati.
Kombucha should be safe for people with diabetes, according to Amati. “However, some commercially available products contain added sugars, so it’s important to check the label.”
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