Perhaps the only kombucha study that meets today's scientific standards came out in the September 2000 issue of Nutrition. A team of researchers from the University of Alaska Fairbanks department of psychology gave kombucha to a group of lab mice. Male mice that drank kombucha lived 5 percent longer than males that didn't drink kombucha; for females, kombucha extended life by 2 percent. Kombucha also inhibited weight gain, even though kombucha-drinking mice ate and drank more than those that didn't drink it. The authors speculated that this could be due to the free xanthines — naturally occurring chemical compounds with the same base as caffeine — in the kombucha stimulating the metabolism. The tea leaves are likely the source of the xanthines, as xanthines are found in green, black, and oolong tea. These results were in line with anecdotal health claims, but that's not all the study found. The mice that were treated with kombucha also developed smaller brains and larger livers and spleens, which are all associated with poor health in humans.