Kombucha Lowers Sugar Levels in People with Type 2 Diabetes

According to the findings of a clinical trial conducted by researchers at Georgetown University’s School of Health, the University of Nebraska-Lincoln, and MedStar Health, people with type 2 diabetes who drank the fermented tea drink kombucha for four weeks had lower fasting blood glucose levels than those who drank a similar-tasting placebo beverage.

This conclusion from a pilot 12-person feasibility trial suggests the possibility of a nutritional intervention that could help lower blood sugar levels in persons with diabetes, as well as laying the groundwork for a bigger trial to validate and expand on these findings. On August 1, 2023, this discovery was published in Frontiers in Nutrition.

Kombucha is a tea fermented with bacteria and yeasts that has been drank in China since 200 B.C., although it did not become popular in the United States until the 1990s. Anecdotal claims of enhanced immunity and energy, as well as reductions in food cravings and inflammation, have boosted its appeal, although evidence of these benefits has been lacking.

“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, 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 said, “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 crossover design involved one group of people drinking about eight ounces of kombucha or placebo beverage daily for four weeks, followed by a two-month period to “wash out” the biological effects of the beverages before swapping the kombucha and placebo between groups for another four weeks of drinking the beverages. Neither group was informed as to which drink they would be receiving at the time.

After four weeks, Kombucha appeared to drop average fasting blood glucose levels from 164 to 116 milligrams per deciliter, but the difference with the placebo was not statistically significant. According to the American Diabetes Association, blood sugar levels before meals should range between 70 to 130 milligrams per deciliter.

The researchers also looked at the composition of kombucha’s fermenting microorganisms to see which elements were the most active. They discovered that the beverage was mostly made up of lactic acid bacteria, acetic acid bacteria, and a type of yeast called Dekkera, with each microbe present in almost equal amounts; the discovery was confirmed by RNA gene sequencing.

“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 2 diabetes.”

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