Kombucha is a fermented tea made with a combination of bacteria and yeasts. Its origins are disputed, but some scholarship claims it was first consumed in Northern China around 5,000 years ago. Prized then for its “detoxifying” properties, kombucha may have gotten its current name from a fifth century physician named Kombu who purportedly used it to cure the digestive problems of a Japanese emperor.
Flash forward 1,600 years, and kombucha has become the darling drink of many health-minded Americans. Its bacteria and yeast populations are thought to bolster the health of the gut’s microbiome — the disparate community of microorganisms that dwell in the gastrointestinal (GI) tract, and appear to play a role in a person’s risk for conditions ranging from autoimmune disorders to depression.
But while many people think of kombucha (and other fermented foods) as “probiotic” — meaning the microorganisms they contain provide some health perk — that term isn’t technically accurate. “You can’t really call it a probiotic because there’s no established health benefit,” says Dr. Emeran Mayer, a professor of medicine and co-director of the Digestive Diseases Research Center at UCLA. “The health claims around kombucha have outpaced the science.”
Unfortunately, science probably won’t catch up any time soon. Studying kombucha is a challenge because, depending on how it’s prepared, the drink can have varying amounts of acidity, effervescence, alcohol, and sugar. Its types and amounts of bacteria and yeast also differ from one preparation to the next. Likewise, the gut’s flora vary from person to person. Predicting how all these variables will interact is a puzzle that experts may never solve, Mayer says.
For the same reasons, it’s tough to gauge how much kombucha is too much. Your gut, your health status, and the type of kombucha you’re chugging are all factors that could determine how you react to the beverage, says Anayansi Escalante-Aburto, a researcher at Mexico’s University of Monterrey who co-authored a 2017 review on kombucha’s health effects.
That said, there may be reasons for some people to go easy on the beverage.
“I don’t know if you should be drinking three or four bottles a day, but I doubt there would be serious side effects”
Kombucha is very acidic, Escalante-Aburto says. For people with reflux or other gut disorders, acidic foods and drinks may exacerbate their symptoms. As a precaution, pregnant women are sometimes advised not to drink kombucha because it may contain an anticoagulant called heparin, which could theoretically raise a woman’s risk for bleeding during delivery. But Escalante-Aburto says the evidence is weak that kombucha contains it. It’s also possible that improperly prepared kombucha could contain potentially harmful levels of bacteria. Still, some of these same warnings could be applied to undercooked meat, improperly stored milk, or almost anything else people ingest.
“There is no clear-cut volume that can be considered as safe,” says Rasu Jayabalan, an assistant professor of food microbiology at India’s National Institute of Technology who published a 2014 review on kombucha’s safety. At the same time, “there are no studies showing consistent health concerns associated with its overconsumption,” he says.
Mayer reiterates many of these points. “If you’re sensitive to its acidity or something else in it, you may have diarrhea or other nonspecific GI symptoms like bloating or pain,” he says. But if a person isn’t experiencing any of these symptoms, he doesn’t see much reason to worry about serious, long-term issues. “I don’t know if you should be drinking three or four bottles a day, but I doubt there would be serious side effects — especially if you’re buying it from a store,” he adds.
Long story short, no one can predict your threshold for kombucha consumption. And that’s assuming you even have one. It’s possible you could swig the stuff all day and never have a problem. It’s also possible that a few ounces could upset your stomach or give you the runs.
But kombucha has been around for thousands of years. “It is consumed worldwide, and the side effects reported are very minimal,” Jayabalan says. If the amount you’re drinking isn’t giving you problems, you probably don’t have much to worry about.