In the past few years, kombucha has made its way out of your weird college friend's cabinet and into the hands of celebrities like Halle Berry and, of course, Gwyneth Paltrow. The fermented tea is touted for its supposed ability to treat a variety of health issues (including everything from tummy troubles to aging), often attributed to the hearty helping of beneficial bacteria in each bottle. But the science is decidedly undecided on the actual benefits of drinking the stuff and, in some rare cases, kombucha may actually come with serious health risks.Kombucha is made by letting black tea and sugar ferment with the help of a starter culture , creating a mushroom-like bacterial clump that sits on top. Thanks to the fermentation, you're also getting some live bacteria when you drink the fizzy, sweet-tart mixture, (and, yes, you're also consuming a bit of alcohol ). These little bugs aren't the same kinds that make you sick. Instead, these bacteria may be necessary for many processes in your body, including regulating your gut health and immune system. Although there's no great evidence to suggest kombucha will cure you of anything, there is some research to suggest that getting more of those bacteria in your diet (either with the help of supplements or real food) may be beneficial for your digestion and mental health However, the truth is that you can only get those bacterial buddies if you go for an unpasteurized version. This poses a slight health risk , and that risk might not even be worth the trouble in terms of benefits.Aside from occasional dizziness and nausea, kombucha has been associated with a few cases of very serious liver damage and a dangerous buildup of lactic acid in the body. While these events are pretty rare, they do happen, and anyone drinking kombucha should know about them. These may be especially serious for pregnant women, young kids, or anyone with a compromised immune system — due to HIV, cancer, or diabetes, for example. That's why experts usually recommend avoiding homemade kombucha (unless you can guarantee that your or your friend's setup is hygienic) and sticking to trustworthy brands when buying it bottled.Both pasteurized and unpasteurized versions are sold in stores. Pasteurization involves heat that kills bacteria (including the good ones) to keep your beverages safe. In lieu of that process, veggie juices , for example, often undergo high-pressure processing instead, which kills bacteria with extreme pressure rather than heat. Juices that aren't treated with heat or pressure are required to carry a warning saying that they "may contain harmful bacteria that can cause serious illness."But for kombucha, anyone making it commercially has to submit a food safety plan to the FDA , according to a special section of the agency's food code, which recommends but doesn't require pasteurization or any type of warning. So, it can be really hard to know (unless you spend time researching it) exactly what process the kombucha you just bought went through before it landed in your store.