It's been spotted in the hands of celebrities, a murky-looking drink with an exotic name: kombucha. The beverage originally hails from China, where it first earned a reputation as a health tonic nearly 2,000 years ago.
In the U.S., kombucha has gone through several reincarnations. Its benefits haven't been proved. What has been shown, for the home-brewed versions, is that it isn't always safe.
Kombucha became popular in the 1980s among the elderly and people with HIV. The drink, at that time largely home-brewed, accrued a reputation for boosting the immune system, increasing energy, improving skin and nails, and reversing the thinning and graying of hair. The beverage was (and still is) made by adding a kombucha "mushroom" -- a pancake-shaped mass of bacteria and yeast often obtained by mail order --to black or green tea and sugar.
The mixture ferments for a week, resulting in a slightly fizzy, sweet and sour (some say undrinkable) beverage containing a long list of amino acids, B vitamins and living things: Acetobacter bacteria and Brettanomyces bruxellensis, Candida stellata, Schizosaccharomyces pombe, Torulaspora delbrueckii and other yeasts.
The commercially brewed kombucha now on store shelves is similar in looks, taste and B vitamin content, but its microorganism profiles can differ from the home-brewed form. Its current popularity probably stems from its purported probiotic properties and reputation as an immune booster, says Dr. Brent Bauer, director of the Complementary and Integrative Medicine Program at the Mayo Clinic in Rochester, Minn. Labels typically boast a shorter list of microorganisms, often Lactobacillus species and a few other bacteria known for beneficial effects on digestion.
Home-brewed kombucha has had problems. Kombucha is acidic enough to kill most harmful bacteria that might try to grow during fermentation, says Yao-wen Huang, a professor at the Center for Food Safety at the University of Georgia in Athens. But harmful molds, such as species of Aspergillus, can grow, and in unsanitary conditions, harmful bacteria can too.
The drink's reputation suffered a blow when kombucha mushrooms contaminated with anthrax led to an outbreak of skin infections in an Iranian village in the mid-1990s. Around the same time, two women in Iowa developed metabolic acidosis -- a dangerous buildup of acid in the body -- after drinking kombucha; one died.
