Unlocking kombucha’s health benefits: Fermented beverage can lower blood sugar spikes, study reveals

21 Feb 2023 --- Researchers found that kombucha reduced the glycemic index (GI) and insulin index (II) when consumed with a high-GI meal, while sugar-free soda water and diet lemonade did not. Lowering blood glucose levels could reduce the risk of diseases such as insulin resistance and diabetes.

When consuming kombucha, the GI value lowered to 68 and II to 70. GI values after the same meal with soda water or diet lemonade amounted to 86 and 84, respectively. These GI values were similar to the consumption of the meal without an accompanying beverage.

Professor Jennie Brand-Miller, one of the study’s authors, notes that nutritionists rarely have something good to say about soft drinks. “But now there’s an exception – we have shown a specific live form of kombucha reduces the blood glucose response to a meal.”

She adds that kombucha “provides an alternative to alcoholic and non-alcoholic beverages and is a simple and enjoyable way to improve health.”

In the clinical trial, a live form of kombucha reduced the blood glucose response to a meal. Health benefits
According to the study, published in Frontiers in Nutrition and conducted at Sydney University’s Glycemic Index Research Service in Australia, high glycemic diets induce high and recurrent surges in blood glucose and insulin levels.

Long-term consumption of such meals could lead to multiple health issues, such as the risk of insulin resistance, development of cardiovascular disease, dyslipidemia, diabetes and certain cancers.

The researchers point to data that low-GI diets could reduce the risk of such diseases, improve blood glucose control and insulin sensitivity in people with diabetes, can be used for weight control and reduce high blood fat levels.

Professor Marc Cohen from the Extreme Wellness Institute Melbourne, Australia, says that the health effects of kombucha have been extensively studied in animals. In these studies, “kombucha has been shown to assist in detoxification, digestion, antioxidation, energy metabolism and immunity.”

He adds, “this is the first controlled clinical trial of kombucha in humans and the first study to show living kombucha reduces postprandial blood sugar spikes when consumed with a meal.”

Kombucha is also marketed for its gut health support, as the fermented drink contains prebiotics, probiotics and post-biotics.

Kombucha popularity
According to Cohen, “Kombucha originated in ancient China where it was labeled the ‘Elixir of Life’ and ‘The Tea of Immortality’ after it was discovered fermented tea produces a delicious, fizzy and tart drink that makes the drinker feel wonderful.”

“Kombucha is the world’s fastest growing functional beverage with a global market of over US$500 million in 2022, so, surprisingly, it’s taken so long to see a published clinical trial of kombucha in humans.”

The researchers note that results cannot be generalized to other kombucha beverages. These may vary in tea base, bacteria and yeast species used as a starter culture and differences in chemicals, metabolites, microbes and antioxidant activities.

Cohen explains that the kombucha used in the study was previously reported to contain 200 microbial species and two and a half times the polyphenol content of green tea.

“This suggests this kombucha is a rich source of probiotics. The kombucha SCOBY (Symbiotic Colony of Bacteria and Yeast) bio-activates the phytochemicals in tea to produce new beneficial nutrients.”

Set-up of the study
The researchers conducted a clinical trial with 11 healthy adults to examine the GI and II after a high-GI meal consisting of Jasmine rice, soy sauce and green peas.

The test participants consumed three reference glucose solutions and three test meals with different beverages. With each test meal, the participants consumed either an unpasteurized kombucha, a diet lemonade soft drink or a soda water. The researchers note that low-GI diets could reduce the risk of diseases such as insulin resistance and diabetes.

The GI or II values were calculated by expressing the two-hour blood glucose and insulin response as a percentage of the reaction produced by the reference glucose solution, consisting of 50g of glucose dissolved in water.

While the soda water and lemonade did not contain sugar, kombucha added 1.7g of sugar to the test meal.

Further research
Cohen adds, “the mechanisms of kombucha’s action on blood sugar are unclear and not all kombuchas are the same.”

The researchers speculate that multiple mechanisms account for the observed effect of kombucha on GI and II values. They point to the complex mix of chemical constituents, live microorganisms’ actions, and kombucha’s low pH.

Moreover, they state that further studies are needed to examine the mechanisms of kombucha and its potential therapeutic benefits.

By Jolanda van Hal

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