Kombucha (Fermented Tea): What Research Shows About the Tea, Safety and Cautions

Check before you drink: kombucha made at home or in a ceramic pot has been linked to serious harm, including lead poisoning [5][6]; it contains some alcohol, and in a Canadian survey about 1 in 3 samples was above the 1% level used to call a drink non-alcoholic there [7]; and Poison Control advises people who are pregnant, or who have a weakened immune system, to avoid it [3]. Kombucha is a tea-based drink (made with true tea from the tea plant, sugar and a living culture), not a herbal tea. This page covers the drink itself. Human trial evidence for health benefits is thin, and we say so below. We give no home-brewing instructions, because home fermentation is not something we advise.

What kombucha is

Kombucha is a sparkling, sugared tea. A sweetened tea infusion is fermented at room temperature for several days with a mat of bacteria and yeast, often called a SCOBY (a "symbiotic culture of bacteria and yeast", also called the tea fungus or "mushroom"). [12] Yeast turn the sugar into alcohol, and acetic acid bacteria turn some of that alcohol into acetic acid, which makes the drink sour. [12] The tea is usually Camellia sinensis (black or green tea), and other plants can be added. [11] Taste: sour (tart) and fizzy, and slightly sweet depending on how long it ferments and what is added. [12] A review says drinking kombucha has been described as early as 220 B.C.; that is history, not proof of benefit. [12] The food-page version of this topic is Kombucha, and the tea plant itself is covered at green tea and black tea. Other fermented foods are in fermented foods safety and home fermentation risks.

Taste, caffeine and how to brew

What research found about the tea itself

Human trial evidence is weak. A systematic review that searched three databases in July 2018 looked at 310 articles and found only one that reported empirical results from human subjects; it found no registered trials either. [8] Reviews describe many benefits, but mostly from lab and animal work, and they call for human trials. [8][11] Two newer randomized trials used a specific green tea kombucha.

The two trials are small, short and used one type of kombucha, so a result does not carry over to every bottle. A review says kombucha varies a lot with the sugar, time and temperature of fermentation. [11] Claims that kombucha "detoxes" the body or "restores gut flora" are marketing; we found no source that supports them. Kombucha-based supplements are a different product from the drink, and a result for one does not carry over to the other.

Check before you drink

• Home-brewed kombucha and contamination. Poison Control says home-brewed kombucha has been associated with several adverse events, including at least one death, cardiac arrest, hepatitis, severe muscle weakness, heart muscle inflammation and skin anthrax, and that contamination is possible if home brewing is not carried out carefully. [3] These are case reports and cannot give a rate.
• Lead from ceramic. A married couple in Australia developed symptomatic lead poisoning needing treatment after drinking kombucha brewed in a ceramic pot for six months; the authors think the acid in the tea pulled lead from the glaze. [5] In a family outbreak in Spain, lead in kombucha made and sold in ceramic containers measured 0.95 to 47 mg/kg in the samples, and the authors named the ceramic containers as the source. [6] The CDC says kombucha should not be prepared or stored in ceramic or lead crystal containers. [1]
• Lactic acidosis (too much acid in the blood). In 1995 two women in Iowa who had drunk kombucha daily for about two months became severely ill with high lactic acid levels; one died and one recovered. The CDC, Iowa and FDA investigation found no known disease-causing organism and did not establish that the tea was the cause. [1] A 2017 case report describes another woman with severe lactic acidosis who recovered after stopping the tea. [15] Single cases cannot show cause.
• Liver. Case reports describe liver injury or severe liver damage after kombucha drinking (2016 and 2023). [13][14] They cannot show cause or how common it is. See liver and kidney cautions.
• Alcohol. The US Alcohol and Tobacco Tax and Trade Bureau (TTB) says a kombucha at 0.5 percent alcohol by volume or more, at any point in production or after bottling, is an alcohol beverage under its rules. [2] In a survey of 684 kombucha samples in British Columbia, the mean was 0.77 percent and the highest 3.62 percent; 31.5 percent of samples were above the 1 percent limit for non-alcoholic drinks there. [7] A New Zealand study found about 22 percent of nine commercial samples above its 1.15 percent limit. [17] Poison Control notes some bottles had up to 3 percent. [3] If you avoid alcohol, check the label. See alcohol in herbal extracts: who should avoid it.
• Pregnancy and breastfeeding. Poison Control says pregnant women should avoid kombucha, store-bought or homemade. [3] A review states that kombucha is contraindicated in infants and pregnant women, though it says the toxic effects are still unclear. [11] The NHS foods-to-avoid page we read does not mention kombucha. Ask your clinician. See pregnancy and breastfeeding.
• Babies and children. Poison Control says young children should not drink it; the same review lists children under 4 as a group where it is contraindicated. [3][11] The FDA says caffeinated drinks should be avoided for children under 2. [4]
• Weak immune system, kidney disease, HIV. Poison Control says people with compromised immune systems should not drink it. [3] The review lists kidney failure and HIV as contraindications. [11] See fermented foods safety.
• Medicines. Proper evidence not found in the sources we read for specific medicine interactions with kombucha as a drink. Not described is not proof of none. Ask a pharmacist. See herbal tea and medicine interactions.
• Iron, kidney stones, allergy, surgery. Not described for kombucha in the sources we read.
• Histamine. See the site page histamine, tyramine and fermented foods.

Tea, capsule or extract?

Kombucha is a fermented drink, not an extract. The "kombucha" in gummies, powders or supplements may not contain the same mix of acids, tea compounds and microbes, and a result for one is not a result for the other. See tea vs tincture vs capsule and the food page Kombucha.

Buying and storing

• Prefer a labeled, commercially made bottle over a homemade one if you choose to drink it; the case reports above are mostly home-brew or ceramic. Read the label for alcohol, sugar and any added juice or herbs. See reading an herbal tea or tincture label.
• Because fermentation can continue after bottling, alcohol can rise in a bottle that is stored warm or for a long time. [2][3]
• General storage: see storing herbal tea and how long it lasts. We found no source with a shelf life for kombucha.

Related pages

• Kombucha (functional foods)
• Green tea
• Black tea
• Fermented foods safety and home fermentation risks
• Caffeine in foods and drinks: official limits
• Herbal tea before surgery