Kombucha’s health benefits may go beyond our guts

The next time you go grocery shopping, don’t forget to pick up a case of kombucha. Tea lovers have long hailed the funky, fermented drink for keeping the gut healthy and running smoothly, and now we can tack on diabetes management to the list of potential benefits.

A small study published on August 1 in the journal Frontiers in Nutrition found kombucha stopped spikes in blood sugar levels for adults with Type 2 diabetes. With the number of Americans with diabetes tripling in the last three decades, the beverage could potentially help lower blood sugar levels and prevent the condition from worsening in pre-diabetics. While the authors have several ideas on how this works, they haven’t found a clear answer or connection just yet.

Kombucha, which is cultured with bacteria and yeast, has been around for centuries but has grown in popularity around the world in the last two decades. “Consuming one to two 8-ounce servings of kombucha daily offers health benefits while keeping sugar and calorie intake in check,” explains Kelsey Costa, a registered dietitian nutritionist at the National Coalition on Healthcare who was not involved in the study. Most brands sold in stores are typically packaged in 16-ounce bottles, making up two servings.

A first-of-its-kind human trial 

Chagai Mendelson, a medical resident at MedStar Georgetown University Hospital and lead author of the new research, came up with the trial idea after speaking with diabetic patients on ways to cut sugar from their diet. His standard medical advice would involve drinking more water and less sugary beverages, but after noticing that more people were drinking kombucha, he was unsure whether the slightly sweet tea was safe to drink. When diving into the research, he noticed several animal studies where kombucha improved glycemic function or helped regenerate beta cells (cells in the pancreas that produce insulin, but can be overworked to the point of death in people with diabetes) Yet he could not find any clinical trials looking at how kombucha affected diabetic individuals in a real-world setting. 

So, Mendelson and his team recruited 12 diabetic patients for a four-month-long pilot study. Finding volunteers was challenging, he says, because there was no funding to pay the subjects for their time and the criteria was highly selective—they had to have Type 2 diabetes and zero history of drinking kombucha. There was also attrition, where people dropped out in the middle of the study or did not respond during follow-up attempts. Ultimately, only seven participants completed the experiment.

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To compensate for the small numbers, the authors took a crossover-trial approach. Each participant served as their own control to allow the team to look at the difference in sugar levels when they drank kombucha versus when they didn’t. Half of the volunteers drank one daily cup of kombucha for four weeks, while the other six drank fizzy non-fermented ginger water that acted as the placebo. They then went through a two-month “wash-out period” where the effects of kombucha would go away, allowing people’s metabolisms to reset. Afterward, the group switched roles; neither half knew which drink they were receiving at any point in the trial. “Even though there’s fewer participants, we get two data points from each one. And it also allows us to make sure that some of that variability is accounted for,” Mendelson explains.

How kombucha might affect blood sugar

After four weeks of drinking kombucha, people went from an average blood sugar level of 164 milligrams per deciliter to 116, which falls well within the American Diabetes Association’s healthy range recommendations. Some individuals were also taking insulin when their blood sugar levels were measured, and could have been on restricted diets.

Mendelson has several thoughts about why regular kombucha intake might make a difference. The first is the substitution theory, where the tea is simply replacing sugary drinks like soda and fruit juice that people typically pair with their meals. The second is the microbiome theory. Kombucha is a great source of probiotics and drinking it helps build a diverse and healthier gut bacteria that aid in processing nutrients and food. “As you’re taking more probiotics, your gut is able to digest carbohydrates in a way where they are released to the blood in a more steady flow,” Mendelson says. “That helps to avoid having high blood sugar after a meal.”

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The third but less popular explanation is that the ingredients in kombucha are helping to create new beta cells. Studies on diabetic rats have shown beta cells can be regenerated by potentially blocking certain enzyme activity in the pancreas that would normally promote carbohydrate digestion, but it’s less clear whether that would translate in humans. The final hypothesis is that when patients have more acetic acid—the chemical compound responsible for kombucha’s acidic taste and smell—in their gut, it causes their digestive system to slow down. That leads to slower absorption of carbohydrates and a gradual, not rapid, increase in blood sugar.

The tea is not a cure

While kombucha is a healthy alternative to sweeter drinks, Mendelson cautions people not to think of it as some magic cure-all. The trial does not provide enough evidence to definitively say it will work better than medication and other healthy dietary habits for reducing blood sugar. 

It’s also possible that kombucha may not help at all. Jorge Moreno, an obesity medicine specialist at Yale Medicine who was not involved in the study, notes two major concerns with the trial. First, the small sample size increases the margin of error and inflates the chances of a false connection between kombucha and blood sugar levels. Second, nine of the 12 participants were using insulin, and their doses could have fluctuated. (Mendelson says people were asked to self-report any changes with their insulin use.) “If the dosage of insulin increased for these participants, that would also lower the glucose blood level and affect their results. More research is needed,” Moreno notes.

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Kombucha may not help everyone with Type 2 diabetes, but the trial shows it’s one of the better drinks they can choose from. If you do want to test the benefits out yourself, Mendelson suggests pairing your diabetes medication with the tea to avoid dangerous blood sugar spikes and lulls.