The name kombucha [(Chinese: chájūn (茶菌), Japanese: kōcha-kinoko (紅茶キノコ), Korean: hongchabeoseotcha (홍차버섯차), Russian: chaynyy grib (чайный гриб)] refers to any of a variety of preparations of fermented, lightly effervescent sweetened black or green tea drinks that are commonly used as functional beverages for their as yet unsubstantiated health benefits. Kombucha is produced by fermenting tea using a "symbiotic 'colony' of bacteria and yeast" (SCOBY). Actual contributing microbial populations in SCOBY cultures vary, but the yeast component generally includes Saccharomyces and other species, and the bacterial component almost always includes Gluconacetobacter xylinus to oxidize yeast-produced alcohols to acetic and other acids.
Beverages referred to as kombucha originated around 5,000 years ago in China, though the English word can only be traced to 1991 and is of uncertain etymology. Historically, kombucha has been home- or locally-brewed; in the late 1990s, commercially bottled kombucha became available in North American retail stores.
Although kombucha has been claimed to be a cure for many diseases, and to confer a wide range of health benefits, there is no good evidence to support these claims. There are several documented cases of adverse effects related to kombucha drinking, and there is the potential for contamination during home preparation. A systematic review found the mostly unclear benefits of kombucha drinking did not outweigh the known risks.
Kombucha is reported to have originated around 5,000 years ago in China; based on Qin dynasty records, it was known as "Divine Che" (Divine Tea) and highly valued as an "energizing" and "detoxifying" drink. Then, according to a reported legend, a Korean doctor named Kombu brought the tea to Japan for Emperor Inkyo in 414 AD as an aid for digestive difficulties. The drink spread to east Russia at least as early as 1900, and from there, to Europe.
The Japanese name for what English speakers know as kombucha is kōcha kinoko 紅茶キノコ (literally, 'black tea mushroom'), compounding kōcha "black tea" and kinoko 茸 "mushroom; toadstool". The Chinese names for kombucha are hóngchájùn 红茶菌 ('red tea fungus'), cháméijūn 茶黴菌 ('tea mold'), or hóngchágū 红茶菇 ('red tea mushroom'), with jūn 菌 'fungus, bacterium or germ' (or jùn 'mushroom'), méijūn 黴菌 'mold or fungus', and gū 菇 'mushroom'. ("Red tea", 紅茶, in Chinese corresponds to English "black tea".) In Russian, the kombucha culture is called chainyy grib чайный гриб (literally "tea fungus/mushroom"), and the fermented drink is called chainyy grib, grib ("fungus; mushroom"), or chainyy kvas чайный квас ("tea kvass"). In Japan, Konbucha (昆布茶?, "kelp tea") refers to a different beverage made from dried and powdered kombu (an edible kelp from the Laminariaceae family).
The English word kombucha has been in use since at least 1991, and is of uncertain etymology. The American Heritage Dictionary suggests that it is probably from the "Japanese kombucha, tea made from kombu (the Japanese word for kelp perhaps being used by English speakers to designate fermented tea due to confusion or because the thick gelatinous film produced by the kombucha culture was thought to resemble seaweed)."
A 1965 mycological study called kombucha "tea fungus" and listed other names: "teeschwamm, Japanese or Indonesian tea fungus, kombucha, wunderpilz, hongo, cajnij, fungus japonicus, and teekwass". Some further spellings and synonyms include combucha and tschambucco, and haipao, kargasok tea, kwassan, Manchurian fungus or mushroom, spumonto, as well as the misnomers champagne of life, and chai from the sea.
Kombucha has been promoted with claims that it can treat a wide variety of human illnesses including AIDS, cancer, and diabetes, and that it can stimulate the immune system, boost the libido and reverse the greying of hair. There is however no good evidence that kombucha consumption benefits human health. In particular, although laboratory experiments are suggestive, no evidence exists from controlled human trials.
In a systematic review of 2003, Edzard Ernst characterized kombucha as an "extreme example" of an unconventional remedy because of the great disparity between implausible, wide-ranging health claims lacking evidentiary support, and the potential for harm the preparations seem to hold. Ernst concluded that the unsubstantiated list of proposed therapeutic benefits do not outweigh the known risks.
Specifically, given its microbial sourcing and possible non-sterile packaging, Kombucha is not recommended in people with poor immune function, in women who are pregnant or nursing, or in children under 4 years old. There are numerous cases of severe adverse reactions to ingesting the drink, and at least one woman died after consuming it, though the death was only discussed in relation to and not unequivocally linked to the drink.
Some adverse health effects may be due to the acidity of the tea, which can cause acidosis, and brewers have been cautioned to avoid over-fermentation. Other adverse health effects may be a result of bacterial or fungal contamination during the brewing process. Topical use of the tea has been associated with anthrax infection on the skin, but in this case, Kombucha contamination may have occurred during storage.
While rigorous study of the toxicity and its molecular agents is yet lacking, an association has been made between symptoms observed in a number of Kombucha toxicity cases, and the presence of the hepatotoxin, usnic acid, a natural product associated with lichen, and reported present in such teas.
Kombucha culture, when dried, becomes a leather-like textile known as a microbial cellulose that can be molded onto forms to create seamless clothing. Using different broth mediums such as coffee, black tea, and green tea to grow the kombucha culture results in different textile colors, although the textile can also by dyed using plant-based dyes. Different growth mediums and dyes also change the textile's feel and texture. The kombucha textile is similar to cellulose and is sustainable and compostable. London-based fashion designer Suzanne Lee presented kombucha textiles in shoes and clothing in 2011 and in 2014, designer Sacha Laurin debuted a clothing collection made entirely out of kombucha textile.
Composition and properties
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A kombucha culture is a symbiotic culture of bacteria and yeast (SCOBY), that contains, as its name implies, one or more species each of bacteria and yeasts, which form a zoogleal mat known as a "mother." The cultures may contain one or more of the yeasts Saccharomyces cerevisiae, Brettanomyces bruxellensis, Candida stellata, Schizosaccharomyces pombe, Torulaspora delbrueckii, and Zygosaccharomyces bailii.
The bacterial component of Kombucha comprises several species, almost always including Gluconacetobacter xylinus (G. xylinus, formerly Acetobacter xylinum), which ferments alcohols produced by the yeasts into acetic and other acids, increasing the acidity and limiting ethanol content. The population of bacteria and yeasts found to produce acetic acid has been reported to increase for the first 4 days of fermentation, decreasing thereafter. G. xylinum has been shown to produce microbial cellulose, and is reportedly responsible for most or all of the physical structure of the "mother".[non-primary source needed]
The mixed, presumably symbiotic culture has been further described as being lichenous, in accord with the reported presence of the known lichenous natural product usnic acid, though as of 2015, no report appears indicating the standard cyanobacterial species of lichens in association with Kombucha fungal components. The association is at least important as an hupothesis, as significant numbers of cases of usnic acid ingestion in herbal supplements or remedies have led to progressions from nausea through jaundice to liver failure—and consequent need for liver transplant—that have been recorded (see the NIH, NIDDK LiverTox database entry for usnic acid, and references therein).
Sucrose is converted, biochemically, into fructose and glucose, and these into gluconic acid and acetic acid, and these substances are present in the drink. In addition, Kombucha contains enzymes and amino acids, polyphenols, and various other organic acids; the exact quantities of these items vary between preparations. Other specific components include ethanol (see below), glucuronic acid, glycerol, lactic acid, usnic acid (an hepatotoxin, see above), and B-vitamins. Kombucha has also been found to contain vitamin C.
The alcohol content of the kombucha is usually less than 1% but increases with fermentation time.
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Commercially bottled kombucha became available in the late 1990s. In 2010, elevated alcohol levels were found in many bottled kombucha products, leading retailers including Whole Foods to temporarily pull the drinks from store shelves. In response, kombucha suppliers reformulated their products to have lower alcohol levels. By 2014 US sales of bottled kombucha were $400 million; $350 million of that was earned by Millennium Products, Inc. which sells "GT's Kombucha". In 2014, the market was projected to have 30% growth, and companies that make and sell kombucha formed a trade organization, Kombucha Brewers International.
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Kombucha has been associated with illnesses and death. A tea made from Kombucha is said to be a tonic, but several people have been hospitalised and at least one woman died after taking this product. The cause could not be directly linked to Kombucha, but several theories were offered, e.g. The tea might have reacted with other medications that the woman was taking, or bacteria might grow in the Kombucha liquid and, in patients with suppressed immunity, might prove to be fatal.
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