A small new study shows the potential glucose-lowering benefits of this fizzy fermented tea.
The popular fermented tea called kombucha may help individuals with type 2 diabetes manage their blood sugar levels.
Findings reported August 1 in the journal Frontiers in Nutrition revealed that individuals with type 2 diabetes who consumed kombucha regularly for four weeks had lower fasting blood glucose levels than when they drank a similar-tasting (although slightly less sour) placebo beverage.
“The study is promising and interesting, because a drink that actually has sugar in it may potentially lower blood sugar,” says one study author, Dan Merenstein, MD, a professor of human sciences in Georgetown’s School of Health and of family medicine at Georgetown University School of Medicine in Washington, DC.
“When participants took a placebo [drink], their blood sugar went down but not that significantly. But when we gave kombucha to the same people — with the same microbiome, the same genetics, and same diet — their blood sugar levels went down impressively,” adds Dr. Merenstein, who collaborated with scientists from the University of Nebraska in Lincoln and MedStar Health, a nonprofit healthcare organization.
Blood Sugar Drops in Relation to Kombucha Consumption
For the study, researchers recruited 12 adults with type 2 diabetes with an average age of 57. Nine were female, and half the group were African American and the other half white. Each participant was instructed to consume 8 ounces of a study drink with dinner every day for four weeks.
During one four-week period, they drank only either kombucha or placebo, and then after an eight-week break to “wash out” the biological effects of the beverages, they switched to drinking the other beverage for four weeks.
Neither group knew which beverage they were receiving at the time.
Each week, participants reported their daily fasting blood glucose levels, which they measured using a home finger-stick testing glucose meter before breakfast. Morning fasting blood glucose levels were selected because this is the most common time when people with diabetes check their sugars.
After four weeks of drinking kombucha, participants’ average fasting blood glucose levels dropped from 164 to 116 milligrams per deciliter (mg/dL). After four weeks of drinking the placebo, average fasting blood glucose levels dipped from 162 to 141 mg/dL, which was not a statistically significant drop.
For adults with diabetes, the fasting blood glucose level (measured before a meal) should ideally be between 80 to 130 mg/dL, according to the American Diabetes Association.
Kombucha Cannot Reverse Type 2 Diabetes
While the study suggests a link between kombucha consumption and improved fasting blood sugars, Marilyn Tan, MD, an endocrinologist at Stanford Medicine in California who was not involved in the research, stresses that the results did not demonstrate diabetes reversal or resolution in any patients.
“This was a very small study, and though it showed an encouraging improvement in fasting blood sugars, we don’t have data on glucose levels throughout the rest of the day [only at one time during the day],” says Dr. Tan, whose main clinical interests are outpatient and inpatient diabetes management. “Diabetes is difficult to reverse, and it depends on the type of diabetes and other contributing factors — for example, other medications that may raise glucoses or the risk of other health conditions like pancreatic disease.”
Exploring the Active Ingredients of Kombucha
In addition to measuring kombucha’s effect on blood sugar, the researchers also looked at the makeup of the fermenting microorganisms in the drink to determine which ingredients might be the most active. They found that the beverage included mostly lactic acid bacteria, acetic acid bacteria, and a form of yeast called Dekkera.
Although the mechanism that may lead to lower blood sugar is unclear, Tan says these ingredients may be linked to changes in the gut microbiome or other metabolic changes at the cellular level.
The study authors speculate that the beneficial mechanism of action may be driven by microbes, but also metabolites found in kombucha, which include ethanol, lactic and acetic acids, tea constituents, and flavoring ingredients.
The Long History of Kombucha as a Health-Promoting Beverage
Kombucha is made from brewed black or green tea and sugar in a process that resembles vinegar fermentation. As with a sourdough starter, the addition of a SCOBY — or symbiotic culture of bacteria and yeast, which forms on the surface of the liquid as the tea ferments — can make the process quicker.
Its production involves yeast fermentation of sugar to alcohol, followed by a bacterial fermentation of alcohol to acetic acid. Vinegar is a combination of acetic acid and water. The alcohol and acetic acid content of kombucha is less than 1 percent, according to the Pennsylvania Department of Agriculture.
Believed to originate thousands of years ago in China, kombucha has long been valued for its potential healing properties.
Research published in the May 2020 issue of Antioxidants suggests that the fermented tea has strong antioxidant properties. Antioxidants are compounds found in food that may reduce inflammation and protect the body.
While the study was limited, with only 12 participants, Merenstein and his team believe the investigation provides a basis for follow-up studies with more participants over a longer period of time.
Tan adds that the research drinks (both kombucha and placebo) were donated by Craft Kombucha, a commercial manufacturer in the Washington, DC area, so there may be some bias. Merenstein stresses, however, that none of the scientists received payment from this company.
Until more research can be conducted, the true benefit of kombucha remains to be seen, Tan says.
“Kombucha is not a replacement for diabetes treatments recommended by your healthcare provider,” she adds.
Merenstein says that someday kombucha could be an adjunct to help people with prediabetes or diabetes. “Hopefully in the future, but we’re not there yet,” he says.
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