Drinking the fermented beverage could lower your fasting blood glucose levels, according to a study published Tuesday in the journal Frontiers.

Researchers from Georgetown University in Washington, D.C., split participants—all Type 2 diabetics—into two groups. One group was given 8 ounces of kombucha to drink before a carb-heavy dinner every evening for four weeks; the other was given a similar-tasting sparkling beverage to drink instead. Then, the groups switched.

Kombucha drinkers lowered their fasting blood sugar levels by about 50 points—from 164 to 115. (The American Diabetes Association recommends a fasting blood sugar of less than 100.) The drop is even more significant given that researchers let participants eat whatever they wanted. While the fasting blood sugar levels of non-kombucha drinkers dropped by about 20 points, the number wasn’t statistically significant, the authors write.

The million-dollar question: Why?

There are a few possibilities, according to researchers. Adding any carbonated drink to dinner may suppress the appetite and reduce meal size, leading to a lower fasting blood glucose in the morning.

Another possibility: Kombucha consumption has been associated with the regeneration of insulin-producing beta cells in the pancreas—in animals, anyway—meaning it might be able to reverse the condition (at least partially). 

Yet another: Compounds contained within kombucha—such as polyphenols, caffeine, organic acids, ethanol, and alkaloids—may prevent oxidative stress-related diseases like heart disorders, cancer, and neurodegeneration. And they may also lower cholesterol and blood pressure, the authors write, pointing to an all-around health-boosting benefit.

There are other theories, too—and more study is needed to determine exactly which contributed to the apparently associated reduction in fasting blood sugars. Other health benefits, including potential improved gut health, were not explored and warrant study, the authors add.

The study included only 12 participants. Still, kombucha shows real health promise, researchers assert.

“An estimated 96 million Americans have prediabetes—and diabetes itself is the eighth leading cause of death in the U.S., as well as a major risk factor for heart disease, stroke, and kidney failure,” Georgetown’s Dr. Chagai Mendelson, a lead author of the study, says in a news release. 

“We were able to provide preliminary evidence that a common drink could have an effect on diabetes. We hope that a much larger trial—using the lessons we learned in this trial—could be undertaken to give a more definitive answer as to the effectiveness of kombucha in reducing blood glucose levels, and hence prevent or help treat Type 2 diabetes.”

Just what is kombucha?

The ancient concoction, consumed as early as 200 BC in China, consists of tea (black or green, usually), sugar (or another sweetener like honey), “healthy” bacteria, and yeast that ferments from a week to a month. The end result: a lightly carbonated drink with a tangy taste. Fermentation adds a tinge of alcohol to the beverage, but not much—usually less than 0.5%, making it technically nonalcoholic.

The drink is popular, no doubt—the global market was worth nearly $1.7 billion in 2019 with predicted annual growth of 20%, according to the study’s authors. And it’s known for its perceived health benefits. But little research has been done on its actual health benefits, if it has any, according to the Cleveland Clinic.

Still, possible pluses, according to the Cleveland Clinic, include…

• Weight loss
• Reduction in inflammation
• Improving gut health
• Boosting immune system
• Fighting cancer
• Detoxification
• Protecting heart health

Consuming the brew is not, however, without risks. Possible side effects from drinking too much kombucha include…

• Headache
• Nausea
• GI troubles
• Ketoacidosis (a condition where there’s too much acid in your blood)

If kombucha is brewed in clay vessels or other containers with lead, lead toxicity is also possible, Cleveland Clinic dietitian Maxine Smith says. Another risk: unsanitary brewing conditions, especially if kombucha is made at home. Smith recommends watching out for odd coloring or a nail-polish–like smell.

“Most of the commercially packaged kombucha at the store is perfectly fine,” she says. “But if you’re at some random flea market and there’s a kombucha table, it might not necessarily be the best place to get it.”