TUESDAY, Aug. 1, 2023 (HealthDay News) -- Kombucha is a fermented tea that many folks believe offers numerous health benefits — and new research suggests they may be right.

Though the study was small -- 12 participants -- it found that kombucha may help lower blood sugar levels in people with type 2 diabetes. Fermented with bacteria and yeasts, the drink has been consumed in China since 200 B.C. but it has been embraced in the United States only since the 1990s, researchers said.

“Apple cider vinegar was really taking off and people were talking about it all the time and kombucha,” said study author Dr. Daniel Merenstein, director of family medicine research at Georgetown University in Washington, D.C. “And they have a farmers market at Georgetown where they sell kombucha, so we just thought, this kombucha is more tasty, easier to drink than apple cider vinegar … so that's really what got us to do this study.”

Not only was it easy to take, participants who drank kombucha had significantly lower average fasting blood sugar levels after drinking it for four weeks -- 116 versus 164 at the study's start, researchers found.

Participants who drank a similarly flavored placebo also saw their blood sugar drop -- from 162 to 141 -- but researchers said that change was not statistically significant.

For the study, participants downed 8 ounces of kombucha or a similarly flavored placebo drink daily for four weeks. Then, after a two-month break to "wash out" the biological effects of the beverages, the drinks were swapped between groups for another four weeks. None of the participants were told what they were drinking.

Though there had been some previous lab and animal studies of kombucha's benefits, Merenstein said researchers believe this is the first examining effects of kombucha in people with diabetes. He hopes it will act as a starting point for further research. Much more study is needed, he said.

Dr. Rifka Schulman-Rosenbaum, director of inpatient diabetes at Long Island Jewish Medical Center and an associate professor at the Zucker School of Medicine at Hofstra/Northwell in New York, reviewed the findings.

She cautioned against looking at these results with too much enthusiasm.

“There's a lot of interest in kombucha and potential health benefits for multiple different conditions, but very little scientific proof of the benefits," she said. "And this study, while it did show a slight lowering on the sugar levels in the kombucha drinkers compared to the other sugary drink, it's hard to make a lot of strong conclusions from this study.”

Schulman-Rosenbaum expressed another concern -- this one about patients themselves.

“I have concerns with patients that focus too much on stuff like this and lose sight of the bigger picture, which is needing to follow up with their doctor, needing to regulate their monitor of their sugar levels, and if they're prescribed medications, take their medications,” she said.

Thought to have been invented in China, kombucha is made by adding certain strains of bacteria, yeast and sugar to black or green tea and allowing it to ferment and produce acetic acid.

During fermentation, the bacteria and yeast form a film called a SCOBY, which is believed to have a probiotic benefit. Devotees also claim the tea helps with an array of health conditions from blood pressure to cancer, though this is largely anecdotal.

“There's really just a lack of data out there and hopefully, this will push people like the NIH [National Institutes of Health] and other people to study these kinds of things,” Merenstein said, “because if it really is true, in a bigger population that a sugar drink can actually lower your blood sugar, that's pretty exciting to figure out the mechanism and just to maybe implement with patients.”

In the meantime, Schulman-Rosenbaum recommends people maintain a healthy lifestyle to combat prediabetes.

“Not only should you be monitoring your physical activity and your food intake and your weight, but you need to have regular doctors’ visits at least once a year, possibly more often depending on what other conditions you have,” she said.

The study received no outside funding and used only one brand of kombucha, made by Brindle Boxer Kombucha. However, the authors said the major bacteria and yeasts in the drink are highly reproducible and likely to be functionally similar between brands.

The findings were published Aug. 1 in Frontiers in Nutrition.

More information

For more on prediabetes, see the U.S. Centers for Disease Control and Prevention.

SOURCES: Daniel Merenstein, MD, professor, human sciences, Georgetown University School of Health, professor and director, family medicine research, Georgetown University School of Medicine, Washington, D.C.; Rifka Chaya Schulman-Rosenbaum, MD, associate professor, Donald and Barbara Zucker School of Medicine at Hofstra/Northwell, Great Neck, N.Y., and chief resident, Long Island Jewish Medical Center, Queens, N.Y.; Frontiers in Nutrition, Aug. 1, 2023