Reviewed and updated, March 2011
Also called "Manchurian mushroom" or "Kargasok mushroom", kombucha is not a mushroom at all but a mixed culture of several species of bacteria and yeasts that grow in black or green tea with added sugar to produce a fermented drink that tastes something like fizzy cider. Over the past few years it has become extremely popular, helped in part by photos of celebrities such as Lindsay Lohan, Halle Berry and Reese Witherspoon carrying bottles of the beverage and in part by promotion of the idea that it's a healthy drink.
Kombucha sipped daily has been recommended as a treatment for everything from AIDS and arthritis to baldness. I've seen claims that it boosts energy and improves eyesight. A few years ago, kombucha was credited with the recovery of a patient suffering from advanced AIDS. Accounts of this seemingly miraculous turnaround left out the fact that the patient had begun treatment with an FDA-approved experimental drug therapy at the same time. While some laboratory studies suggest that kombucha may have some health benefits (one published in January 2009 in the Journal of the Science of Food and Agriculture investigated potential cholesterol-lowering and antioxidant effects), no human study has been published showing a beneficial effect for kombucha.
I am also concerned about the possibility of contamination in home-brewed kombucha. Some batches contain aspergillus, a toxin-producing fungus. This would be a significant risk for individuals with compromised immune systems, such as those with AIDS or in chemotherapy for cancer. There have been reports in the medical literature of adverse reactions, including nausea, vomiting and headaches, in people drinking more than four ounces of kombucha tea daily.
In 2009, physicians at Cedars-Sinai Hospital in Los Angeles reported a life-threatening case of lactic acidosis (the build-up of lactic acid in the bloodstream faster than it can be removed) and acute kidney failure in a 22-year-old man newly diagnosed with HIV within a few hours of his consuming kombucha tea. Other cases of lactic acidosis and cases of serious liver dysfunction associated with ingestion of kombucha tea have also been reported, along with allergic reactions, jaundice, and head and neck pain. I would particularly caution pregnant women, nursing mothers, the elderly, children and anyone with a compromised immune system against consuming it.
In summary, I know of no health benefits to be gained by drinking kombucha tea.
Andrew Weil, M.D.