BREAKING NEWS: Kombucha Lowers Blood Sugar Levels in People with Diabetes
Hard on the heels of the February 2023 study by scientists at Sydney University that drinking living kombucha with a meal reduces postprandial glucose spikes, a new study conducted by researchers at Georgetown University’s School of Health, the University of Nebraska-Lincoln and MedStar Health reports that people with type-II diabetes who drank kombucha for four weeks had lower fasting blood glucose levels compared to when they consumed a similar-tasting placebo beverage.
The August 1, 2023 report in Frontiers in Nutrition titled ‘Kombucha tea as an anti-hyperglycemic agent in humans with diabetes – a randomized controlled pilot investigation’ is the first clinical trial examining effects of kombucha in people with diabetes.
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, stated “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 had one group of people drinking about eight ounces of kombucha or placebo beverage daily for four weeks and then after a two-month period to ‘wash out’ the biological effects of the beverages, the kombucha and placebo were swapped between groups with another four weeks of drinking the beverages. Neither group was told which drink they were receiving at the time.
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 researchers also looked at the makeup of fermenting micro-organisms in kombucha to determine which ingredients might be the most active. They found that the beverage was mainly comprised of lactic acid bacteria, acetic acid bacteria, and a form of yeast called Dekkera, with each microbe present in about equal measure; the finding was confirmed with RNA gene sequencing.
The kombucha was produced specifically for the study by Craft Kombucha, Washington, DC. The placebo drink was an unfermented sparkling drink, also prepared by Craft Kombucha specifically for the study and intended to be similar to the kombucha in flavor and appearance. The placebo was made from heat-treated ingredients, cooled, diluted with water, and carbonated. Both the kombucha and placebo were sweetened with sucrose and flavored with the same amount of freeze-dried ginger powder to match flavor profiles.
The researchers thanked Craft Kombucha founder Tanya Maynigo-Loucks for donating the kombucha and for creating and donating the placebo drink for the study. And that “Craft Kombucha did not have any access to data reported in this study. No author has any financial ties with Craft Kombucha.”
As noted in the Fall 2020 issue of SYMBIOSIS Magazine, the researchers first contacted Tanya via KBI in 2019.
Robert Hutkins, a professor at the University of Nebraska – Lincoln, who studies the microbiology of fermented foods, contacted KBI. He was looking for a collaborator for a study being conducted by Georgetown Medical Center on human subjects to study the impact of kombucha consumption on blood sugar levels of people with diabetes. KBI has assisted other studies in the past by connecting them with local brands to donate their products for research. Tanya eagerly agreed, and the paper is awaiting publication.SYMBIOSIS, Fall 2020, p.42
Beneficial effects of kombucha
In a section of the report worth quoting at length, the scientists note:
Other possible mechanisms of action may also contribute to glycemic benefits of kombucha. First, as observed in animal models, kombucha was associated with improved pancreatic beta cell regeneration which could contribute to improved endogenous insulin production. Second, chemical constituents formed by kombucha microbes may influence host metabolism and provide health benefits. These constituents include polyphenols, D-saccharic acid-1,4-lactone, caffeine, organic acids, ethanol, and various alkaloids. Based on in vitro and animal studies, several of these compounds have been proposed to prevent oxidative stress-related diseases, such as cardiovascular disorders, cancer, and neurodegeneration, as well as reducing cholesterol levels and blood pressure. Third, kombucha has been suggested to contain constituents that reduce starch digestion and reduce net absorbed glucose. Kombucha also contains acetic acid, which has been reported to have anti-diabetic properties, although at higher concentrations than the kombucha used in our study. Furthermore, other studies have reported the absence of an anti-glycemic effect. Notably, this non-commercial kombucha also contained 1.5% ethanol which, according to several reports, is unlikely to have affected blood or serum glucose levels. Ultimately, larger studies will be needed to elucidate the exact mechanism of action.
Good news for diabetics
The report notes:
Despite the sugar used in the fermentation process of kombucha, daily consumption did not raise fasting blood glucose levels to unhealthy levels in diabetics. This is clinically significant as many diabetics struggle to consume only water and counseling diabetic patients on drink choice is challenging for physicians.
Based on self-reported health outcomes, kombucha was well tolerated, as most individuals reported average or better health measures before and after treatment.
Our results showed that consumption of kombucha for 4 weeks resulted in significant decreases in fasting blood glucose levels in diabetic subjects with elevated blood glucose levels (>130 mg/dL) compared to baseline, whereas smaller changes in fasting blood glucose observed following consumption of placebo were not significant.
The full report, which goes into great detail about the study methodology, and an elaborate analysis of the chemistry of the kombucha used, down to microbiological analysis via “16S rRNA gene sequencing for bacteria and ITS sequencing for fungi” is available online.