Kombucha, the fermented tea drink lauded by celebrities for its gut health benefits, is facing increased scrutiny from experts who question the extent of its health advantages and warn of potential downsides. While the beverage has surged in popularity, with annual sales exceeding $1.6 billion, researchers and food scientists point to a lack of large-scale human studies to support many of the health claims, such as improved digestion and reduced blood sugar.
Food scientist Dr. Jennifer Auchtung stated that while some small studies, primarily in animals, have suggested potential health benefits, robust human trials are still needed. The purported gut-healthy bacteria in kombucha also raise questions, as the precise mixture and quantity of microbes can vary significantly between brands. Experts note that not all live bacteria survive digestion, making it unclear if kombucha acts as an effective probiotic delivery vehicle. "We do think having the dead bacteria present may boost the immune system or fuel beneficial microbes, so the number of bacteria in the drink could still be useful," Auchtung explained, "But in terms of kombucha as a delivery vehicle for a probiotic, it's really probably not the best that you could consume."
A 2025 review of eight human studies found only limited evidence suggesting kombucha might ease gastrointestinal symptoms and increase healthy gut bacteria, but researchers emphasized the need for more comprehensive studies. For individuals with irritable bowel syndrome, some sugars in kombucha that are not fully absorbed can be fermented by gut bacteria, potentially leading to bloating and discomfort.
Experts advise consumers to pay close attention to sugar content, with Dr. Auchtung recommending choosing brands with no more than ten grams of sugar per serving. Some popular varieties, such as Health-Ade Kombucha, can contain up to 18 grams per 16-ounce bottle, comparable to two Original Glazed Krispy Kreme donuts. Other brands like Synergy typically contain around 16 grams, while KeVita averages ten grams, with flavor variations impacting sugar levels.
Kombucha naturally contains small amounts of caffeine and alcohol due to its tea base and fermentation process, generally considered negligible for the average consumer. "For the average person, kombucha can be part of a healthy diet," Auchtung said. "There are modest health benefits and it definitely won't do you any harm if consumed in moderation."
Dietitian Tiffany Bruno added that while kombucha can support gut health, it is not a universal solution. She stressed the importance of adequate fiber intake from a varied diet, noting that an estimated 95 percent of Americans do not consume enough fiber. For those seeking alternatives, unsweetened green tea offers beneficial compounds without added sugar, while kefir, a fermented milk drink, is suggested as a more research-backed option for digestive health due to its higher concentration of live bacteria.