The results of a clinical trial carried out by researchers at Georgetown University’s School of Health, the University of Nebraska-Lincoln, and MedStar Health showed that people with type-II diabetes who drank the fermented tea beverage kombucha for four weeks had lower fasting blood glucose levels compared to when they drank a similar-tasting placebo beverage.
This result from a pilot 12-person feasibility trial suggests the possibility of a dietary intervention that could help diabetics lower their blood sugar levels and also lays the groundwork for a bigger trial to validate and build upon these findings.
This finding was reported in Frontiers in Nutrition on August 1, 2023.
Kombucha is a tea fermented with bacteria and yeasts and was consumed as early as 200 B.C. in China, but it did not become popular in the U.S. until the 1990s. Anecdotal reports of increased immunity, more energy, decreased food cravings, and decreased inflammation have helped to increase its popularity, but there hasn’t been any concrete evidence to support these claims.
“Some laboratory and rodent studies of kombucha have shown promise and one small study in people without diabetes showed kombucha lowered blood sugar, but to our knowledge, this is the first clinical trial examining effects of kombucha in people with diabetes,” says the study author Dan Merenstein, M.D., professor of Human Sciences in Georgetown’s School of Health and professor of family medicine at Georgetown University School of Medicine. “A lot more research needs to be done but this is very promising.”
Merenstein continued, “A strength of our trial was that we didn’t tell people what to eat because we used a crossover design that limited the effects of any variability in a person’s diet.”
According to the crossover design, one group of participants drank about eight ounces of kombucha or a placebo beverage every day for four weeks. Then, after a two-month break to “wash out” the biological effects of the drinks, the kombucha and placebo were switched between groups for a subsequent four weeks of consumption. Neither group was told which drink they were receiving at the time.
Some laboratory and rodent studies of kombucha have shown promise and one small study in people without diabetes showed kombucha lowered blood sugar, but to our knowledge, this is the first clinical trial examining effects of kombucha in people with diabetes. A lot more research needs to be done but this is very promising.
Dan Merenstein
Kombucha appeared to lower average fasting blood glucose levels after four weeks from 164 to 116 milligrams per deciliter while the difference after four weeks with the placebo was not statistically significant. Guidelines from the American Diabetes Association recommended blood sugar levels before meals should be between 70 to 130 milligrams per deciliter.
The composition of the kombucha’s fermenting microorganisms was also examined by the researchers to see which components might be the most potent. Using RNA gene sequencing, they discovered that the beverage was primarily made up of lactic acid bacteria, acetic acid bacteria, and a type of yeast called Dekkera, with each microbe present in almost similar amounts.
The kombucha used in this study was produced by Craft Kombucha, a commercial manufacturer in the Washington, DC, area. It has been re-branded as Brindle Boxer Kombucha.
“Different studies of different brands of kombucha by different manufacturers reveal slightly different microbial mixtures and abundances,” says Robert Hutkins, Ph.D., University of Nebraska-Lincoln and the study’s senior author. “However, the major bacteria and yeasts are highly reproducible and likely to be functionally similar between brands and batches, which was reassuring for our trial.”
“An estimated 96 million Americans have pre-diabetes and diabetes itself is the eighth leading cause of death in the U.S. as well as being a major risk factor for heart disease, stroke, and kidney failure,” says Chagai Mendelson, M.D., lead author who was working in Merenstein’s lab at Georgetown while completing his residency at MedStar Health.
“We were able to provide preliminary evidence that a common drink could have an effect on diabetes. We hope that a much larger trial, using the lessons we learned in this trial, could be undertaken to give a more definitive answer to the effectiveness of kombucha in reducing blood glucose levels and hence prevent or help treat type-II diabetes.”
Additional study authors at Georgetown University are Sabrina Sparkes, a student in the School of Health, Varun Sharma, and Sameer Desale. In addition to Hutkins, Chloe Christensen, Jennifer M. Auchtung, Car Reen Kok and Heather E. Hallen-Adams are at the University of Nebraska-Lincoln.
