Kombucha is a fizzy, slightly sour fermented tea made by adding a culture of bacteria and yeast, often called a SCOBY, to sweetened black or green tea. It’s popular as a “gut health” drink, and it does contain live microbes and some acids from fermentation. But the evidence for specific health benefits in people is very limited: a systematic review found only one study reporting results of kombucha in human subjects, and concluded that its claimed benefits need to be tested in clinical trials. Kombucha can be part of a healthy diet in moderation, but watch the sugar content, and take care with homemade versions, unpasteurized drinks in pregnancy, and the small amount of alcohol it contains.
How kombucha is made
- Black or green tea is brewed and sweetened with sugar.
- The cooled tea is mixed with a SCOBY (symbiotic culture of bacteria and yeast) and some kombucha from a previous batch.
- Over 7 to 14 days, the yeast and bacteria ferment the sugar, producing acids, carbon dioxide and a little alcohol.
- The kombucha is often bottled with fruit or ginger for a second fermentation, which adds flavor and fizz.
Much of the sugar is used up during fermentation, but the amount left varies widely between brands.
Possible benefits
Live microbes
Unpasteurized kombucha contains live bacteria and yeasts. Fermented foods may support a more diverse gut microbiome; our article on probiotic foods explains what the evidence shows for fermented foods in general. However, the types and amounts of microbes in kombucha vary, and they haven’t been shown to have specific health effects.
A lower-sugar alternative to soft drinks
Many kombuchas contain less sugar than regular soft drinks, so swapping a sugary drink for a low-sugar kombucha is a reasonable choice.
Tea compounds
Kombucha made from green or black tea contains some of the tea’s polyphenols. Our guide to green tea benefits covers what’s known about tea.
What’s not proven
Claims that kombucha protects the liver, strengthens the immune system, prevents cancer or aids weight loss come mainly from lab and animal studies, as the review notes. They haven’t been tested properly in people.
Downsides and risks
Sugar
Some kombuchas contain several grams of sugar per bottle, and others are sweetened further with juice. Check the label and choose lower-sugar versions. Free sugars should be limited to 30 g a day for adults, according to the NHS.
Acidity and teeth
Kombucha is acidic, which can wear tooth enamel if you sip it throughout the day. Drink it with meals, and rinse your mouth with water afterward.
Alcohol
Fermentation produces a small amount of alcohol. Commercial kombucha sold as a soft drink is usually below 0.5% alcohol, but homemade and some “hard” kombuchas contain more. People who avoid alcohol completely, are pregnant, or are in recovery from alcohol problems should check labels.
Unpasteurized drinks
Most kombucha is unpasteurized. The FDA warns that children, older adults, pregnant women and people with weakened immune systems risk serious illness from drinking untreated juices, and the same caution applies to unpasteurized kombucha. These groups should avoid it or check with their doctor.
Homemade kombucha
Brewing at home carries a risk of contamination with harmful bacteria or mold if equipment isn’t clean or the brew isn’t acidic enough. Never brew or store kombucha in ceramic or lead-glazed containers, as the acid can draw out lead. Use clean glass jars and follow a reliable method. If a batch smells unusual, looks moldy or tastes off, throw it away.
Digestive upset
Drinking a lot of kombucha, especially if you’re not used to fermented foods, can cause bloating or an upset stomach. Start with a small glass.
How much is sensible?
There’s no official limit. For most healthy adults, a small bottle or glass (about 120 to 250 ml) a day, as part of a balanced diet, is reasonable. Water should remain your main drink. Our guide on how much water to drink explains why.
Kombucha on keto
Some kombuchas are low enough in sugar to fit occasionally on keto, but others contain too much. Check the carbohydrate content on the label. Our guide to keto drinks lists lower-carb choices.
How to choose a kombucha
- Check the sugar: look for less than about 5 g of sugar per 100 ml, and avoid versions with added fruit juice concentrate or syrups.
- Check the alcohol content, especially if you need to avoid alcohol.
- Look for “refrigerate” on the label if you want live cultures; shelf-stable versions are often pasteurized.
- Be wary of health claims on the bottle, such as immunity or weight loss, which aren’t backed by good evidence.
- Compare price: kombucha is often expensive, and plain water, tea or a glass of kefir may suit you better.
Kombucha vs other fermented foods
If you want fermented foods for gut health, yogurt and kefir with live cultures, sauerkraut, kimchi and miso are good options. Yogurt and kefir have more evidence behind them and provide protein and calcium too.
Common questions
Does kombucha contain caffeine?
Yes, a small amount, because it’s made from tea. Most bottles contain much less caffeine than a cup of coffee, but check the label if you’re sensitive to caffeine or drink it in the evening.
Can I drink kombucha every day?
A small glass a day is fine for most healthy adults, as long as you choose a low-sugar version and drink it with meals to protect your teeth.
Is kombucha good for gut health?
It contains live microbes, but there’s no good evidence yet that it improves gut health in people. A varied diet with plenty of fiber, plus fermented foods such as yogurt and kefir, is a well-supported approach.
Can children drink kombucha?
It’s not recommended for young children because it’s unpasteurized, acidic and contains traces of alcohol.
Is kombucha a probiotic?
Some kombuchas contain live microbes, but “probiotic” means a specific strain with proven health benefits, which kombucha doesn’t generally have.
This article is general information, not medical advice. Talk to your doctor or a registered dietitian before making big changes to how you eat, especially if you have a health condition, take regular medication, or are pregnant or breastfeeding.
