For this crossover 12-person feasibility trial, participants diagnosed with type 2 diabetes drank eight ounces of kombucha fermented tea for four weeks while controls drank a similar-tasting placebo beverage. After a 2-month washout period to clear the biological effects of the beverages, the drinks were swapped between the groups for another four weeks.
Those in the kombucha groups were found to have lower fasting blood glucose levels compared to the controls at the end of the study period, pointing to the potential of kombucha as a dietary intervention to help lower blood sugar levels in those with diabetes and basis for larger trials to confirm as well as expand upon these result.
Kombucha is a tea fermented with bacteria and yeast that dates back to as early as 200 BC in China. This drink started to become popular in Western cultures in the 1990s, being bolstered with anecdotal claims of improved energy, and immunity as well as decreased feeling of hunger cravings and reductions in inflammation, but proof of these benefits has been limited.
“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 study author Dan Merenstein, MD, professor of human science 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.”
The makeup of the fermenting microorganisms in the kombucha was also looked at in an attempt to determine which ingredients may be the most active. The kombucha used was produced by Craft Kombucha and has been rebranded as Brindle Boxer Kombucha. Results which were confirmed with RNA gene sequencing showed that the drink consisted mainly of acetic acid bacteria, lactic acid bacteria, and Dekkera yeast, with each microbe present being in about equal measures.
“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, MD, 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 2 diabetes,” said Mendelson.
