Kombucha refers to any of a variety of fermented, lightly effervescent sweetened black or green tea drinks that are commonly used as functional beverages for their 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-brewed or locally brewed; in the late 1990s, commercially bottled kombucha became available in North American retail stores. It is known in Chinese as chájūn (茶菌), Japanese as kōcha-kinoko (紅茶キノコ), Korean as hongchabeoseotcha (홍차버섯차) and Russian as chaynyy grib (чайный гриб).
Kombucha has been claimed to cure many diseases and to have a wide range of health benefits; however, there is a lack of high-quality 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 that the mostly unclear benefits of kombucha drinking did not outweigh the known risks, thus should not be recommended for therapeutic use.
Kombucha is reported to have originated around 5,000 years ago in China; based on Qin dynasty records, it was known as 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,[not in citation given] 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 provides other beneficial effects such as stimulation of the immune system, boosting the libido, and reversal of gray hair. However, evidence of kombucha's beneficial effects in humans is lacking. In particular, although animal and in vitro experiments suggest that kombucha consumption may be beneficial, as of 2014 no controlled human trials have been conducted to confirm these conclusions.
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 did not outweigh the known risks, and that Kombucha should not be recommended for therapeutic use.
Adverse effects associated with kombucha consumption include severe hepatic (liver) and renal (kidney) toxicity as well as metabolic acidosis. One woman was reported to have died after consuming kombucha though the cause of death was 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. Some studies have found the hepatotoxin usnic acid in kombucha, although it is not known whether the cases of damage to the liver are due to the usnic acid contamination or to some other toxin.
Due to 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.
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
A kombucha culture is a symbiotic culture of bacteria and yeast (SCOBY), similar to mother of vinegar, containing 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, 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", which may have been selectively encouraged over time for firmer (denser) and more robust cultures by brewers.[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.
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 (a 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.
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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