Human Trial Reports Kombucha Benefits

Thanks to Lou Dillon of Twisted Kombucha for sharing news about a significant human study conducted at the Australia Institute, exploring the intriguing world of kombucha nutrition. In the first controlled clinical trial in humans, results showed that living kombucha reduces postprandial glucose spikes when consumed with a meal.

The February, 2023 report in Frontiers in Nutrition titled ‘Glycemic index and insulin index after a standard carbohydrate meal consumed with live kombucha: A randomised, placebo-controlled, crossover trial‘ notes that, despite centuries of anecdotal evidence about the benefits of drinking kombucha, no controlled trials have been published on its effect on humans.Until now.

The scientists at the University of Sydney, Australia, conducted a randomized placebo-controlled, cross-over study that examined the Glycemic Index (GI) and Insulin Index (II) responses after a standardized high-GI meal consumed with three different test beverages (soda water, diet lemonade soft drink and an unpasteurized kombucha) in 11 healthy adults. The study was prospectively registered with the Australian New Zealand Clinical Trials Registry.

They found that:

There was no statistically significant difference in GI or II between the standard meal consumed with soda water (GI: 86 and II: 85) or diet soft drink (GI: 84 and II: 81, (p = 0.929 for GI and p = 0.374 for II). In contrast, when kombucha was consumed there was a clinically significant reduction in GI and II (GI: 68, p = 0.041 and II: 70, p = 0.041) compared to the meal consumed with soda water. These results suggest live kombucha can produce reductions in acute postprandial hyperglycemia.

The report goes into extensive details about the beverages used and the carbohydrate-rich meal consumed to spike the GI and II (“a test portion of microwave Jasmine rice and frozen green peas were combined together in a bowl and cooked in the microwave for 1 min on high.”). The glycemic response was mapped after the test meals were eaten.

Important findings

The report summary highlights the importance of these findings, which

…suggest consumption of kombucha with meals could have important health consequences. Long term consumption of high glycemic diets, which induce high and recurrent surges in blood glucose and insulin levels, increase the risk of insulin resistance, dyslipidaemia, and the development of cardiovascular disease, non-insulin-dependent diabetes mellitus and certain cancers. Conversely, epidemiological and experimental data show that low-GI diets can reduce the risk of these diseases, improve blood glucose control and insulin sensitivity in people with diabetes, reduce high blood fat levels, and can be useful for weight control.

However, the underlying reasons for the benefits are not clear, they speculate:

• Drinking kombucha with a meal conforms to the slow down the rate of starch digestion and absorption as previously reported with other fermented foods.
• Low pH beverages alone do not explain the measured benefits “only the kombucha reduced the postprandial glucose response.”
• The presence of antinutrients, such as tannins in kombucha, which was made from both oolong and green teas, may have also slowed the rate of carbohydrate digestion by binding to the main starch digestion enzyme, alpha-amylase.
• It is also possible that acid-tolerant micro-organisms in the kombucha metabolized some of the glucose in the warm environment of the stomach.
• However, the results cannot be generalized to other kombucha beverages as variation in tea bases, the bacteria and yeast species used as a starter culture, and specific fermentation conditions contribute to large differences in the chemicals, metabolites, microbes, and antioxidant activities of different kombucha products.

Summary

The measurable benefits were due to a variety of factors:

It is likely that multiple mechanisms are in play and that the low pH of kombucha, the complex mix of chemical constituents including high levels of organic acids, polyphenols and tannins, and the actions of live micro-organisms micro-organisms all helped to produce the observed reductions in postprandial glucose and insulin responses. While enhanced postprandial glucose regulation is likely to have many flow-on health benefits, there may be additional benefits from regular kombucha consumption due to changes in the gut microbiota, improvements in islet beta cell function, function or reductions in insulin resistance, inflammation, or damage to the intestinal barrier, which have been observed with regular kombucha consumption in animals.

Further studies examining the mechanisms and the potential therapeutic benefits of kombucha on postprandial glycemia in different populations are warranted.

Note: The study was designed with the help of Australian Good Brew Kombucha (Brunswick, Victoria) who state they “paid to do two clinical trials on kombucha.”

Will other brands step up and fund scientific research into the effects of kombucha on humans?