Kombucha tea shows promise in lowering blood sugar levels for type 2 diabetics

By Dr. Sanchari Sinha Dutta, Ph.D.Reviewed by Benedette Cuffari, M.Sc.Sep 25 2023

In a recent study published in Frontiers in Nutrition, researchers discuss the results of a  randomized controlled pilot clinical trial conducted at the Georgetown University Hospital investigating whether kombucha tea can reduce blood glucose levels in diabetic patients.

Study: Kombucha tea as an anti-hyperglycemic agent in humans with diabetes – a randomized controlled pilot investigation. Image Credit: stockcreations / Shutterstock.com

Background

Diabetes is the ninth leading cause of death worldwide. In addition to a heightened mortality risk, diabetes can also increase the risk of many health complications, including cardiovascular, renal, neurological, and ophthalmological complications.

The global prevalence of type 2 diabetes has increased by more than 400% in the past 30 years. In the United States alone, about 15% of the population is currently living with type 2 diabetes.

Kombucha is a beverage with many reported health benefits, including anticancer, antidiabetic, antimicrobial, antidepressant, and cardioprotective properties. Kombucha is prepared by fermenting sweetened tea with a symbiotic consortium of bacteria and yeasts. Organic acids or other fermentation end-products, bioactive tea components, and added flavoring agents present in kombucha might be responsible for its health-promoting properties.

Study design

This single-center randomized controlled trial (RCT) was conducted at Georgetown University Medical Center in Washington, DC. A total of 12 adult patients with type 2 diabetes were enrolled in the trial.

Study participants were asked to consume 240 ml of a study drink, either kombucha or placebo, with dinner every day for four weeks. After an eight-week wash-out period, the participants consumed 240 ml of the alternate drink every day for another four weeks. The study was double-blinded, as both researchers and participants were unaware of the drink type being consumed during the study.

Participant-reported fasting blood glucose levels were collected at baseline as well as one and four weeks during each intervention period. All study participants also reported secondary health outcomes through a questionnaire that included overall health, insulin requirement, gut health, skin health, mental health, and vulvovaginal health parameters.

The analysis of kombucha microbiota was conducted by selective culturing, 16S ribosomal ribonucleic acid (rRNA) gene sequencing of bacteria, and internal transcribed spacer (ITS) sequencing of fungi. The key components found in kombucha were measured and quantified by high-performance liquid chromatography (HPLC).

Important observations

The consumption of kombucha for four weeks significantly reduced the average fasting blood glucose levels in diabetic patients. Importantly, this effect was not observed in individuals consuming the placebo drink. 

Although the difference in fasting blood glucose levels between baseline and week four was statistically significant among study participants who consumed kombucha, no significant difference in fasting blood glucose levels was observed at week four between placebo-treated and kombucha-treated participants.

Among participants who consumed kombucha during the study period, two had baseline fasting blood glucose levels within the target range set for adult diabetic patients. Considering participants with baseline blood glucose levels above this target range, a significant difference in anti-hyperglycemic effect was observed between the placebo drink and kombucha at week four.

The microbiological analysis of kombucha showed a high abundance of lactic acid bacteria, acetic acid bacteria, and yeast. The 16S rRNA gene sequencing confirmed that lactic acid and acetic acid bacteria were the most abundant bacteria in kombucha, whereas ITS sequencing confirmed that the most abundant yeast was Dekkera.

The chemical analysis revealed that lactic and acetic acids were the primary organic acids present in kombucha at concentrations of less than 1% each. In addition, ethanol was present at a concentration of 1.5%.

Study significance

The trial observations indicate that kombucha can lower fasting blood glucose levels in adult diabetic patients. Kombucha might have suppressed participants' appetite and subsequently reduced their meal size, which reduced fasting blood glucose levels.

Previous studies have demonstrated that consuming kombucha can increase insulin production in pancreatic beta cells. Moreover, some components of kombucha are known to reduce glucose absorption in the intestine. Taken together, these factors can collectively contribute to the anti-hyperglycemic effects of kombucha.

Despite these promising results, more studies with larger sample sizes are needed to establish the health benefits of kombucha in patients with type 2 diabetes.