Photo: Jeff Harris

Have you spotted the newcomer alongside your grocery's selection of bottled jasmine, green, and oolong tea? Called kombucha, it's a fermented tea, and it has become one of the most popular products in the natural and organic market.

Typically made by steeping a gelatinous colony of yeast and bacteria in sweetened black or green tea, kombucha is said to boost the immune system, increase energy levels, and help treat conditions ranging from intestinal disorders to arthritis and cancer. Yet not a single human study or clinical trial supports these claims. However, there is some scientific evidence that suggests kombucha—at least when brewed at home—can cause toxic and allergic reactions, stomach upset, and even death. The bottom line? Until research backs up kombucha's much-touted health benefits—and establishes its safety—it's best to avoid it, says Brent Bauer, MD, director of the Complementary and Integrative Medicine Program at the Mayo Clinic. —Lauren Dzubow

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