As mentioned in the green tea article, tea only comes from one plant: Camellia sinensis, everything else, such as herbal ‘teas’ is technically an infusion. And then there’s the new kid on the block: kombucha tea, which has been enjoying a surge of popularity over the past few years. While its history isn’t well known, it has purportedly been consumed by people from various parts of Asia, including China, Tibet, Russia, and Siberia for over 2000 years, and was introduced into Germany at the turn of the 20th century.
What is Kombucha Tea?
Kombucha tea is a fermented beverage made from tea, sugar, bacteria, and yeast. Some refer to the beverage as ‘kombucha mushroom tea’ because of the film that grows on top of the beverage, which has the shape and color of a flat mushroom. However, the film is not a mushroom at all: it’s a colony of bacteria and yeast, referred to as a ‘SCOBY’ or ‘symbiotic culture of bacteria and yeast’.
The beverage is made by adding the bacteria and yeast colonies to the tea and sugar, and allowing the mixture to ferment for 7 to 14 days, resulting in a fizzy, effervescent beverage that contains vinegar, lactic acid, small amounts of alcohol, B-vitamins, active ‘probiotic’ bacteria and yeast, and other compounds. Because there are several different types of yeast and bacteria that can grow under these conditions, those found in different kombucha teas will vary greatly, resulting in a non-standardized product: not all kombucha teas will be the same.
What are the health benefits of kombucha tea?
The primary benefits of kombucha tea have been linked primarily to its yield of probiotics. Also known as ‘good’ bacteria, probiotics have been widely studied, particularly for their generally positive influence on digestive and immune health, and even management of overweight and related disorders.
There is no shortage of health claims for kombucha tea, ranging from optimizing skin health and digestion – including improving liver function and preventing and treating diarrhea – to boosting the immune system and cancer prevention. More sensationalized claims include countering baldness, insomnia, arthritis, chronic fatigue syndrome, and AIDS – extraordinary claims that currently lack solid evidence.
What would be needed to support these assertions are well designed human studies – studies that use a standardized product so that the exact composition of bacteria and yeast in the beverage are known, applied in humans with specific health issues. However, the scientific research is currently only at the laboratory and animal model stage. The latter have revealed key components of the studied kombucha product that may have promising antioxidant1 , liver-protective2,3, anti-cholesterol (especially in diabetes)4, and kidney-protective5 effects, among others.
Health claims are based on testimonials, which can be highly unreliable. Even the claims around the probiotic content of a specific kombucha tea would have to be regarded cautiously, since both the type and amount of bacteria and yeast present may vary greatly between batches, affecting potential probiotic effectiveness.
Are there any potential health risks?
On the one hand people have been safely making food products like kombucha for thousands of years – not just teas, but also kefir, sauerkraut, kimchi, and more. On the other hand, there have been some reports of complications. Potential concerns surround individual reactions to the SCOBY (including allergy6 and/or food-borne illness7), and the container in which the fermentation process occurs8 in homemade versions. Because cultures and preparation methods vary, kombucha tea may contain other contaminants such as molds and fungi, some of which can cause illness. If the mixture ferments in a jar or urn made of potentially toxic materials that can leach out, adverse health effects can occur.
Aside from selecting the proper container (glass is considered ideal), the safety of kombucha tea rests greatly on how the starter batch is made. During the initial process, when the tea, sugar, bacteria, and yeast are fermenting, the SCOBY forms and floats on top of the beverage; after 7 to 14 days, the SCOBY is removed and transferred to a fresh batch of tea and sugar to start the process all over again. Part of the SCOBY can be passed on to other people so that they can start their own culture, or it can be kept for new batches after the original SCOBY ‘goes bad,’ indicated when it turns dark brown, black, or green. Depending on how the product is handled and prepared, some express concern about potential food borne illness, and some cases have been reported. There have been reports of serious complications linked to the tea, including hospitalizations for abnormal levels of acid levels in the body9 and lead poisoning in people who used ceramic pots8, as well as death7, but a direct causal relationship to the tea itself hasn’t been confirmed.
Because there hasn’t been any credible, well-conducted human research conducted on kombucha tea to support claims of its health-related benefits, it’s impossible to make recommendations for its use in that context. If prepared properly, with the appropriate attention give to reducing the risk for contamination and food-borne illness – such as selecting a glass jar or bottle for fermentation, washing hands before handing the product, using fresh SCOBY, keeping utensils clean, etc. – it can at least be a safe beverage to consume, and at best, may be a source of probiotics.
1. Bhattacharya S, Gachhui R, Sil PC. Effect of Kombucha, a fermented black tea in attenuating oxidative stress mediated tissue damage in alloxan induced diabetic rats. Food Chem Toxicol. 2013 Jul 29;60C:328-340.
2. Wang Y, Ji B, Wu W, Wang R, Yang Z, Zhang D, Tian W. Hepatoprotective effects of kombucha tea: identification of functional strains and quantification of functional components. J Sci Food Agric. 2013 May 28.
3. Murugesan GS, Sathishkumar M, Jayabalan R, Binupriya AR, Swaminathan K, Yun SE. Hepatoprotective and curative properties of Kombucha tea against carbon tetrachloride-induced toxicity. J Microbiol Biotechnol. 2009 Apr;19(4):397-402.
4. Aloulou A, Hamden K, Elloumi D, Ali MB, Hargafi K, Jaouadi B, Ayadi F, Elfeki A, Ammar E. Hypoglycemic and antilipidemic properties of kombucha tea in alloxan-induced diabetic rats. BMC Complement Altern Med. 2012 May 16;12:63.
5. Gharib OA. Effects of Kombucha on oxidative stress induced nephrotoxicity in rats. Chin Med. 2009 Nov 27;4:23.
6. Srinivasan R, Smolinske S, Greenbaum D. Probable gastrointestinal toxicity of Kombucha tea: is this beverage healthy or harmful? J Gen Intern Med. 1997 Oct;12(10):643-4.
7. Sabouraud S, Coppéré B, Rousseau C, Testud F, Pulce C, Tholly F, Blanc M, Culoma F, Facchin A, Ninet J, Chambon P, Medina B, Descotes J. Environmental lead poisoning from lead-glazed earthenware used for storing drinks. Rev Med Interne. 2009 Dec;30(12):1038-43.
8. Centers for Disease Control and Prevention (CDC). Unexplained severe illness possibly associated with consumption of Kombucha tea–Iowa, 1995. MMWR Morb Mortal Wkly Rep. 1995 Dec 8;44(48):892-3, 899-900.
9. SungHee Kole A, Jones HD, Christensen R, Gladstein J. A case of Kombucha tea toxicity. J Intensive Care Med. 2009 May-Jun;24(3):205-7.