Kombucha tea is a sour, effervescent beverage that can be made in your own kitchen, purchased in healthy food stores like Whole Foods or ordered in upscale NYC eateries and the Google corporate cafeteria. Fans of the beverage extol its many benefits, including improved digestive health, appetite suppression and increased energy. But skeptics argue that these benefits are unproven by medical studies and that the bacteria in the fermented brew can be dangerous. So what exactly is this seemingly divisive beverage?

"Kombucha tea is fermented drink made with tea, sugar, bacteria and yeast," says Dr. Brent A. Bauer of the Mayo Clinic in Rochester, Minnesota. "The resulting liquid contains vinegar, B vitamins and a number of other chemical compounds."

Why fans drink kombucha

People who swear by the healing powers of kombucha say the drink can help with a wide range of ailments. According to WebMD, there's "insufficient evidence" for these claims, but kombucha fans often say the beverage helps with:

Risks? Benefits?

Bauer is familiar with the health benefits attributed to kombucha tea, including stimulation of the immune system, cancer prevention and improvements in both digestion and liver function. But, as director of the Department of Internal Medicine's Complementary and Integrative Medicine Program at the Mayo Clinic, he says that "because there are no studies documenting that it [kombucha tea] provides a specific benefit and because there are at least a few case reports of people being harmed by it, I tell my patients who ask to steer clear."

While kombucha is not recommended for people who are sick, it does seem to make some healthy people feel even healthier. Magdalena Schmidt, a professional nursing student in Brooklyn, New York, began making kombucha at home when a friend gave her a "mother," also called a SCOBY, which is an acronym for symbiotic colony of bacteria and yeast. SCOBYs are available for sale and swap all over the Internet, as are instructions for making your own home brew safely.

"You get a lead-free glass jar, two gallons of water, black or green tea and a cup of sugar," Schmidt says. "Cover with a cheese cloth or something similar, put it in a warm place and wait approximately a week."

The tea is ready when the bacteria have multiplied, the mother has split and the mother has spawned a baby SCOBY.

bottled kombuchaIf you're new to kombucha, start drinking it a little at a time. (Photo: Apelavi/Shutterstock)
Starting slowly

As a nursing student and a vegan cook, Schmidt understands the need for safety, so she started off drinking only a couple ounces at a time.

"The acids clean your insides, and then the probiotics in the beverage boost the healthy microflora that is needed in your gut," says Schmidt, who added kombucha to her diet very slowly. "Too much of a good thing is different than a dangerous one. But, to keep kombucha safe, you have to be vigilant about your preparation, make sure everything is very antiseptic. And if you see any mold in the liquid or on the mother, you need to throw out the entire batch."

Post-workout drink

Mike Schwartz, who trained to be a chef at the Culinary Institute of America in Hyde Park, New York, and teaches at the Institute of Culinary Education, is a co-owner of BAO Food and Drink, the first Kombucha tea company to get licensed by the New York State Department of Agriculture. BAO tests the brew daily to make sure it has the proper pH balance and the right bacteria.

Schwartz and his partners began the company because they enjoyed the benefits of home-brewed kombucha and wanted to make it available to men and women looking for a healthier beverage to replace soda or energy drinks.

"It's great after a workout," says Schwartz. "It helps prevent the buildup of lactic acid in your muscles, boosts your energy, and helps you get more nutrition from the food you eat."

Potential side effects

Because it's very difficult to keep kombucha utterly germ-free, it's not recommended for anyone with a weakened immune system or for women who are pregnant or breastfeeding. Kombucha could affect the blood sugar level of people with diabetes. Because kombucha contains caffeine, it isn't recommended for people with issues such as diarrhea or irritable bowel syndrome (IBS). The caffeine could irritate those conditions and make them worse.

This story was originally written in March 2012 and has been updated with the latest information.

The risks and benefits of kombucha tea
Skeptics say the fermented drink's benefits are unproven by medical studies, but kombucha tea enthusiasts extol its many virtues.