Kombucha (also tea mushroom, tea fungus, or Manchurian mushroom when referring to the culture; botanical name Medusomyces gisevii) is a fermented, slightly alcoholic, lightly effervescent, sweetened black or green tea drink commonly intended as a functional beverage for its supposed health benefits. Sometimes the beverage is called kombucha tea to distinguish it from the culture of bacteria and yeast. Juice, spices, or other flavorings are often added to enhance the taste of the beverage. The exact origins of kombucha are not known. It is thought to have originated in Northeastern China where the drink is traditionally consumed, or in Russia and Eastern Europe. Kombucha is now homebrewed globally, and also bottled and sold commercially by various companies.
Kombucha is produced by fermenting sugared tea using a symbiotic culture of bacteria and yeast (SCOBY) commonly called a "mother" or "mushroom". The microbial populations in a SCOBY vary; the yeast component generally includes Saccharomyces cerevisiae, along with other species; the bacterial component almost always includes Gluconacetobacter xylinus to oxidize yeast-produced alcohols to acetic acid (and other acids). Although the SCOBY is commonly called "tea fungus" or "mushroom", it is actually "a symbiotic growth of acetic acid bacteria and osmophilic yeast species in a zoogleal mat [biofilm]". The living bacteria are said to be probiotic, one of the reasons for the drink's popularity.
Numerous implausible health benefits have been attributed to drinking kombucha. These include claims for treating AIDS, aging, anorexia, arthritis, atherosclerosis, cancer, constipation, and diabetes, but there is no evidence to support any of these claims. Moreover, the beverage has caused rare cases of serious adverse effects, including fatalities, possibly arising from contamination during home preparation. Therefore, the potential harms from drinking kombucha outweigh any unclear benefits, so it is not recommended for therapeutic purposes.