Kombucha

Kombucha is a variety of fermented, lightly effervescent sweetened black or green tea drinks that are commonly intended as functional beverages for their supposed 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.

Although it has been claimed to have numerous health benefits, there is no good evidence that drinking kombucha has such effects. By contrast, there are several documented cases of serious adverse effects, including fatalities, related to kombucha drinking, possibly arising from contamination during home preparation. Since the mostly unclear benefits of kombucha drinking do not outweigh the known risks, it is not recommended for therapeutic use.

Kombucha originated in what is now Manchuria around 220 BCE, and is said to have been imported to Japan around 400 CE by the physician Kombu. It is commonly drunk in the United States.

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. Many people use it for medicinal purposes. However, evidence of kombucha's beneficial effects in humans is absent.

...
Wikipedia