In the past few years, kombucha has gone from a hippie beverage to one with mainstream appeal. Because most people find that its tart, sour taste must be acquired, kombucha’s rise in popularity can best be attributed to its purported benefits, which range from aiding weight loss and stopping gut problems to boosting energy and staving off cancer. Given its ubiquity on Whole Foods and Target shelves as well as in restaurants and bars, it may come as a surprise that there is little scientific evidence to back up these health claims. But that doesn’t mean you have to avoid it. Here’s what you need to know.
What is kombucha?
Primarily comprising fermented tea and sugar, the fizzy drink’s roots can be traced back to China during the Tsin or Qin Dynasty around 221 B.C., when it was referred to as “the tea of immortality,” according to Hannah Crum, author of The Big Book of Kombucha!.
While trade routes that led from Northeast Asia toward Russia and Eastern Europe gave the beverage exposure, and Russia, Great Britain, Germany, and Mexico were experimenting with kombucha by the 1800s, the drink temporarily fell out of favor in the early 20th century due to rationing of tea and sugar during World War II.
It wasn’t until the early 2000s that kombucha consumption really increased in the United States—likely due to the positive health claims, says Erica R. Jones, MD, a board-certified internal medicine physician based in Dothan, Alabama. In 2016, PepsiCo bought the kombucha manufacturer KeVita, bringing the drink to the masses. Now the drink is more popular than ever: Consumers spent more than $412 million on organic kombucha in 2018—an increase of 42% compared with 2017, according to Nielsen.
But what exactly is kombucha? The fermented tea beverage is made of black or green tea, white sugar, and SCOBY, an acronym for Symbiotic Culture of Bacteria and Yeast, according to Crum.
Simply put, she explains, it’s a living organism that secretes an enzyme which breaks table sugar into simpler sugars: glucose and fructose. That process, called fermentation, generates carbon dioxide (CO2)—also known as fizz—and trace amounts of ethanol, a chemical compound known as a simple alcohol, which acts as a preservative to prevent molds from colonizing the brew.
But that’s not all: The SCOBY’s bacteria consumes the ethanol and simple sugars, then yields a host of byproducts including acetic acid, vitamin C, and tea polyphenols (or micronutrients from certain plant-based foods), and trace amounts of amino acids.
The resulting drink is tangy yet a little sweet, and can be infused with herbs, fruit, and other flavors.
10 kombucha health benefit claims, reviewed by science
As popular as kombucha is—particularly among the über-health-conscious set—there’s actually not a whole lot of science to back up any of the widespread health claims. While it is possible to extrapolate the benefits of kombucha based on health claims linked to its components, more research is definitely needed. The authors of a 2019 Annals of Epidemiology meta-analysis that reviewed 310 articles on kombucha concluded just as much: They found no controlled studies of human subjects, and no articles on the drink’s health benefits. With that in mind, here’s what science as to say about kombucha’s rumored benefits:
The claim: Kombucha boosts your immune system.
The facts: “Kombucha analysis demonstrates that it contains acetic acid, gluconic acid, vitamin C, B vitamins, amino acids, and other elements that boost health and immunity,” Crum says. Unfortunately, there’s no clinical research that proves kombucha itself directly boosts your immunity.
That said, there is research from the journal Food Microbiology that confirms kombucha’s fermentation process may provide some beneficial bacteria that produce cytokines, or proteins that rev up the immune system and suppress inflammatory proteins, according to Dr. Jones.
And yet? “Any benefits can be attributed to the bacterial cultures and byproducts that result from the fermentation process—not necessarily to kombucha itself,” she says.
The claim: Kombucha helps you lose weight.
The facts: Kombucha’s alleged weight-loss benefits are likely linked to the green tea it’s sometimes made with. “Green tea has been found to have thermogenic, or heat-producing, properties and the ability to promote fat oxidation [when consumed regularly in larger quantities],” Dr. Jones says.
While drinking green tea may play some role in calorie burn, there’s no evidence that directly links kombucha-guzzling to weight loss. Plus, most commercial kombuchas still provide calories from sugar, which may render the mild boost from tea extracts null and void.
The claim: Kombucha contains antioxidants.
The facts: One of the buzziest terms in the health food industry, “antioxidants are compounds that stop the process of oxidation—a chemical reaction that produces harmful free radicals [or reactive molecules] that can destroy healthy cells in the body and are linked to heart disease, diabetes, and cancer,” Dr. Jones says.
Green tea is packed with proven antioxidants like catechins, like the powerful compound epigallocatechin gallate (EGCG), and polyphenols, which make up around 30% of the weight of fresh, dry green tea leaves, according to research from the journal Chinese Medicine. “Kombucha made from this tea contains many of the same compounds, but more research is needed to show any antioxidant-benefit from consumption,” Dr. Jones says.
Some research published in the Journal of Microbiology and Biotechnology and Biomedical and Environmental Sciences shows that regularly drinking kombucha reduces liver toxicity in rats by up to 70%—another benefit that could be linked to the antioxidant levels of tea in kombucha—but there hasn’t been any research done on humans to show similar effects.
The claim: Kombucha aids in digestion.
The facts: Diverse, healthy gut bacteria appears to be correlated with better health and digestive functioning. Because it’s fermented with probiotics, which suppress disease-causing bacteria and improve the intestinal barrier for better nutrient absorption and protection against potentially harmful invaders, kombucha could have digestive benefits, Dr. Jones says.
Science supports the theory: “Research shows that kombucha has a good amount of antibacterial properties that are used to combat undesirable bacteria and yeast in the gut,” explains Dr. Niket Sonpal, MD, a gastroenterologist with the Touro College of Osteopathic Medicine in New York City.
Two more potential perks of the fermented beverage stem from its acetic acid content, which may increase fat-digesting enzymes and hydrochloric acid, which help your body digest fats and break down proteins, respectively. All that said, more research is needed on kombucha and its impact on your digestive tract.
The claim: Kombucha reduces the risk of cancer.
The facts: Kombucha helped prevent the growth of human cancer cells in a 2008 lab study published in the Journal of BUON, and additional lab research published in 2013 in the journal Biomedicine & Preventive Nutrition found that kombucha decreased the survival of human cancer cells.
Dr. Sonpal chalks up these results to antioxidants and polyphenols in the drink's tea component; those compounds may block the mutation and bulking of cancer cells.
Outside the laboratory, there haven’t been any studies to prove that kombucha directly reduces the risk of cancer in humans just yet.
The claim: Kombucha reduces blood pressure.
The facts: “Kombucha contains probiotics and, depending on the effectiveness of those probiotics and our body’s response to them, those probiotics can help reduce blood pressure,” Dr. Sonpal says. That said, the link is theoretical.
Researchers have also noted that tea polyphenols promote smooth muscle relaxation, which can prevent high blood pressure, according to a scientific review published in CyTA - Journal of Food in 2018. Again, there’s very little research to directly link kombucha to reduced blood pressure, and more research is needed.
The claim: Kombucha reduces the risk of heart disease.
The facts: In research conducted on rats in 2012 and on ducks the year before, kombucha delayed the absorption of “bad” LDL cholesterol while significantly increasing “good” HDL cholesterol—two important markets for heart disease. The results could be attributed to the antioxidants found in green tea which may accelerate the elimination of cholesterol and free radicals through the feces, Dr. Sonpal explains.
“The health findings are more related to the benefits of tea, which is one of the ingredients of kombucha,” Dr. Jones says, citing 2015 meta-analysis that associates increased tea consumption with a reduced risk of coronary heart disease, cardiac death, stroke, cerebral infarction, and intracerebral hemorrhage, as well as total mortality in humans.
Green tea has also been shown to inhibit LDL oxidation, which may contribute to heart disease, according to research published in the journal Atherosclerosis. And more recent research published in the Journal of Nutrition found that green tea drinkers have up to a 31% lower risk of developing heart disease—but that doesn’t necessarily mean the benefits can be extrapolated to kombucha.
The claim: Kombucha increases energy levels.
The facts: Because kombucha only contains small doses of caffeine—the average eight-ounce cup of tea contains between 29 and 47 milligrams of caffeine depending on the kind and concentration of tea—it won’t deliver the immediate jolt you might get from coffee. That said, it could theoretically improve your overall energy levels in part due to trace amounts of B vitamins and iron, which are also important for turning food into energy and fending off iron deficiencies, respectively, according to Dr. Sonpal says.
The claim: Kombucha helps rid the body of toxins.
The facts: Like many fruits and veggies, kombucha contains gluconic acid, an antioxidant-like compound that prohibits the action of more harmful environmental compounds that can lead to cell-damage over time—and essentially expedites the process of eliminating these “toxins” through your body, Dr. Sonpal explains. That said, while kombucha was associated with detoxification in a 2014 review of scientific literature published in the Journal of Medicinal Food, the exact mechanism hasn’t been specified.
One theory: The drink’s live bacteria and enzymes can help multiply and diversify the gut’s bacteria. Alternatively, kombucha may aid in liver function by expediting the removal of these compounds from your bloodstream, Dr. Sonpal says—and your liver’s main role is detoxification. Actually, studies on rats have shown that regular kombucha consumption may help to reduce liver tissue damage caused by chemical compounds found in our everyday environment, and may be beneficial in reducing risk of liver disease over time. But more research is needed on human subjects.
The claim: Kombucha helps manage type 2 diabetes.
The facts: Consumption of sugar-sweetened beverages—kombucha included—is not linked to a decrease in diabetes risk. But drinking green tea on its own might be helpful: A 2006 study published in the Annals of Internal Medicine found that people who drank six or more cups of green tea a day had a 33% lower likelihood of developing type 2 diabetes compared with people who drank less than a cup of week.
What are the health risks associated with kombucha?
Despite all the alleged benefits, kombucha has had some negative headlines. In 1995, the Centers for Disease Control and Prevention (CDC) issued a warning after several cases of unexplained severe illness linked to kombucha consumption were reported in Iowa, where one woman went into cardiac arrest and died. In 2009, a man was hospitalized after drinking kombucha potentially led to a build-up of lactic acid in his bloodstream, though genetics and individual metabolism may have played a significant role.
While those risks are rare, the average consumer may find that kombucha leads to stomach issues, infections, and allergic reactions, according to the Mayo Clinic. And “because the pH of kombucha is very acidic, it has the potential to compromise tooth enamel,” Dr. Jones says.
The amount of sugar in kombucha can also be problematic for your oral and physical health—particularly since there can be major discrepancies in how much sugar is reported on a drink’s nutrition label and what’s actually in the drink, according to a 2016 sugar-testing study of competing kombucha brands. Most of the tested products contained 20% more sugar than listed; one brand had a sugar content that was 311% greater than the label amount.
Then there’s the mold factor—mold can cause irritations of the eyes, throat, or skin; make you nauseous; and, if you have a pre-existing mold allergy, put you in an even more dire situation, Dr. Sonpal says.
What’s more, “black, white, or blue powder may form on the surface of the kombucha liquid if the process fails due to improper temperature, weak culture or starter liquid, or using dehydrated or refrigerated cultures,” Crum says. And because there is no regulatory oversight on production practices of homemade versions, the risk of contamination from external sources is high—particularly in DIY versions, Dr. Jones says. “Home kitchens may not provide a completely sterile environment, and mold or other bacteria may enter the liquid,” she explains.
For instance, should lead leak from your ceramic kitchenware and enter the fermenting liquid, drinking it could subject you to a condition as serious as lead poisoning, the Mayo Clinic reports. The CDC also warns against DIY kombucha because of the potential of disease-causing fungi. It’s why it’s best to avoid making kombucha at home and stick to store-bought versions—although they’re not necessarily immune to contamination, either.
The upshot: Is kombucha good for you?
It’s true that kombucha may provide some health benefits. “Kombucha is a nutrient-dense, fermented food,” Crum says. “Like all foods with nutrients in living form, it provides acids, vitamins, and sugars that support a healthy body.”
But it’s not a magic wellness drink. In fact, many of the health benefits ascribed to kombucha are actually linked to the green tea therein—and brewing up a cup of tea is a lot less expensive than buying the fermented beverage.
If you’re interested in trying kombucha to see if the highly hyped benefits are worth it, opt for a store-bought version to avoid any extra risks. And, as always, remember that kombucha should never replace medical treatment—there’s no proof that it’s a miracle cure.
Ashley Mateo has over a decade's worth of experience covering fitness, health, and lifestyle topics for national magazines and websites. She is also a UESCA-certified running coach.
This article was reviewed for accuracy in July 2021 by Angela Goscilo, MS, RD, CDN, manager of nutrition at WW. The WW Science Team is a dedicated group of experts who ensure all our solutions are rooted in the best possible research.