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Chances are, you've seen it in your local grocery store. Maybe you've even mustered the courage to taste it — or at least take a whiff.
Once mostly a product of health food stores and hippies' kitchens, kombucha tea is now commercially available in many major grocery stores.
And people aren't necessarily scooping it up for its flavor. Its taste has been described as somewhere between vinegar soda and carbonated apple cider.
So why shell out $4 bucks for a small bottle of the stinky tea?
Many folks are banking on the potential health benefits of kombucha, including disease prevention, energy improvement and perhaps even turning back the clock and inhibiting aging.
"I've seen claims that kombucha might help kill cancer, is a powerful detoxifier, even a fountain of youth," says Monica Reinagel, a nutritionist and creator of the podcast Nutrition Diva.
Sound fantastical? Well, it probably is.
The bottom line is that we know very little about kombucha and how it may affect health.
"There is really very little evidence to support any kind of claims about kombucha tea," says Andrea Giancoli, spokesperson for the Academy of Nutrition and Dietetics. "So we don't know if it does anything at all."
Nevertheless, most kombucha drinks contain live bacteria. And evidence is mounting that friendly bacteria or probiotics aide digestion and possibly even strengthens the immune system.
These good bugs "actually live inside of us and help digest our food, digesting particles we can't digest on our own," nutritionist Reinagel says. "And they actually produce certain nutrients for us, which is a very nice trick."
Kombucha was popular back in the early '90s, when health-minded consumers produced the tea in their home kitchens. Many HIV-positive individuals consumed it in hopes of boosting their immune systems.
The process of making kombucha is fairly simple. Black or green tea is sweetened with sugar. A concoction of bacteria and yeast is added. The mixture is then fermented in a glass or ceramic container for at least a week.
During this time, microbe production speeds up as the bacteria feast on the added sugar, grow and multiply. The end result looks like a rubbery disc that forms on top of the tea, called the SCOBY, or "symbiotic colony of bacteria and yeast."
It's a thriving colony of microorganisms — billions of them, converting sugar into vinegar and other aromatic compounds. The sheer number of bacteria makes it very difficult to know for sure if the concoction includes only the friendly, good bacteria.
One of the most popular brands of kombucha tea, GT's Kombucha, sells millions of bottles a year. Officials say they test their tea and know it contains at least two important strains of good bacteria.
But that may not be the case for all products now available in supermarkets.
And if you brew it at home, dietitian Giancoli has a warning: "You've got to have really very sanitary conditions and know what you're doing." Otherwise, she says, your tea could get contaminated by not so friendly — or even harmful — bacteria.
In stores, the bottled versions are produced in carefully controlled environments and are likely safe. So if you like the idea of kombucha and if it makes you feel better or more energetic, then there's probably "no harm" in drinking it, nutritionist Reinagel says.
As for the extraordinary health claims — we'll just have to wait until researchers test them out.
Copyright 2013 NPR.