Q: Your article on fermented foods (April, 2026) recommended a drink called kombucha. I’ve never heard of it. Can you tell me what it is and where I can find it?
A: Judith C. Thalheimer, RD, LDN, executive editor of Tufts Health & Nutrition Letter, answers: “Kombucha (kuhm-BOO-chuh) is fermented tea that originated as early as 220 B.C. in Asia. It is typically made from sweetened black or green tea. The fermentation is produced by adding a gel-like symbiotic colony of bacteria and yeast (referred to as a SCOBY) and letting the mixture sit for one to three weeks. The bacteria and yeast feed on the sugars, reducing the sugar content and sweetness of the tea and producing carbon dioxide bubbles and trace amounts of some B vitamins (including thiamin and niacin). The bacteria remain in the mixture, meaning kombucha is a probiotic food (it supplies the gut with beneficial bacteria). The final product is slightly fizzy with a tart, somewhat vinegar-like taste. It is often flavored with fruit (like berry or apple) or spices (like ginger) and is served cold.
“Note that fermentation of sugar also creates alcohol. While the kombucha found in stores is typically regulated to contain less than 0.5 percent alcohol by volume (which is just one-tenth of what is found in a typical beer), home-brewed versions may have more. There is also some caffeine from the tea.
“Claims that kombucha can help prevent and manage serious health conditions are as yet unproven. But this lightly sweet, fizzy, naturally low-calorie drink is a smart swap for soda and other sweet drinks. Swirl the tea gently before drinking to distribute the live, active bacteria cultures that may help support a healthy gut microbiome.
“Kombucha can be found in the refrigerated drink sections of many markets, especially those that say they focus on more ‘natural’ or ‘healthy’ foods.”
Roger A. Fielding, PhD, is a senior scientist in the Metabolism & Basic Biology of Aging directive at the Human Nutrition Research Center on Aging, professor of biochemical and molecular nutrition at the Friedman School of Nutrition Science and Policy, and professor of Medicine at Tufts University School of Medicine.
