People with type II diabetes who drank a fermented kombucha tea drink for four weeks had lower fasting blood sugar levels compared to those who consumed a similarly flavored placebo drink, according to the results of a clinical trial. conducted by researchers from the Georgetown University School of Public Health, the University of Nebraska-Lincoln and MedStar Health. This finding from a 12-person pilot feasibility study points to the potential for a dietary intervention to help lower blood sugar levels in people with diabetes, and also sets the stage for a larger study to confirm and extend these results.
This finding was reported in Limits in nutrition on August 1, 2023
Kombucha is a tea fermented with bacteria and yeast and was consumed as early as 200 BC in China, but did not become popular in the US until the 1990s. Its popularity is supported by anecdotal claims of improved immunity and energy and reduced appetite and inflammation, but evidence for these benefits is limited.
Some laboratory and rodent studies of kombucha are promising, and a small study in people without diabetes showed that kombucha lowered blood sugar, but to our knowledge, this is the first clinical trial examining the effects of kombucha in people with diabetes. Much more research needs to be done, but this is very promising.”
Dan Merenstein, MD, study author, professor of humanities at Georgetown School of Public Health and professor of family medicine at Georgetown University School of Medicine
Merenstein continued, “The strength of our experiment was that we weren’t telling people what to eat because we used a crossover design that limited the effects of any variability in a person’s diet.”
The crossover design had one group of people drink about eight ounces of kombucha or a placebo drink daily for four weeks, and then after a two-month period to “wash out” the biological effects of the drinks, the kombucha and placebo were swapped between groups for another four weeks drinking the drinks. Neither group was told which drink they were taking at that time.
Kombucha appeared to reduce average fasting blood sugar levels after four weeks from 164 to 116 milligrams per deciliter, while the difference after four weeks with placebo was not statistically significant. The American Diabetes Association guidelines recommend blood sugar levels before meals be between 70 and 130 milligrams per deciliter.
The researchers also looked at the composition of the fermenting microorganisms in kombucha to determine which ingredients might be most active. They found that the drink consisted mainly of lactic acid bacteria, acetic acid bacteria and a form of yeast called Decker, with each microbe present in roughly equal proportions; the finding was confirmed by RNA gene sequencing.
The kombucha used in this study was produced by Craft Kombucha, a commercial producer in the Washington, DC area. It has been renamed Brindle Boxer Kombucha.
“Different studies of different brands of kombucha from different manufacturers reveal slightly different microbial mixes and abundances,” said Robert Hutkins, Ph.D., University of Nebraska-Lincoln and lead author of the study. “However, the underlying bacteria and yeast are highly reproducible and likely to be functionally similar between brands and batches, which was reassuring in our experience.”
“Approximately 96 million Americans have prediabetes—and diabetes itself is the eighth leading cause of death in the U.S., as well as a major risk factor for heart disease, stroke, and kidney failure,” said Chagai Mendelson, MD, lead author who worked in Merenstein’s lab. in Georgetown while completing his residency at MedStar Health. “We were able to provide preliminary evidence that a simple drink can have an effect on diabetes. We hope that a much larger study can be undertaken using the lessons learned in this study to give a more definitive answer to the effectiveness of kombucha in reducing blood sugar levels and therefore preventing or aiding in treatment of type II diabetes.”
Additional authors of the Georgetown University study are Sabrina Sparks, a graduate student in the School of Public Health, Varun Sharma, and Sameer Desail. In addition to Hutkins, Chloe Christensen, Jennifer M. Auchtung, Car Reen Kok and Heather E. Hallen-Adams are at the University of Nebraska-Lincoln.
The authors would like to express their gratitude to Tanya Mainigo, founder of Craft Kombucha for providing the kombucha and placebo kombucha for this study. She teaches kombucha classes in Washington, DC, and is launching a new brand of her favorite brew this year called Brindle Boxer Kombucha.
Georgetown University Medical Center
Mendelsohn, S., et al. (2023) Kombucha tea as an antihyperglycemic agent in people with diabetes – a randomized controlled pilot study. Limits in nutrition. doi.org/10.3389/fnut.2023.1190248.