Overview

Kombucha begins as sweetened tea (typically black or green) fermented by a SCOBY — a symbiotic culture of acetic-acid bacteria and yeast that forms a rubbery “mother” on the surface. Over roughly one to two weeks, the culture consumes sugar and produces organic acids (mainly acetic acid, giving kombucha its vinegar-like tang), carbon dioxide (natural carbonation), trace alcohol, and a population of live microbes carried over into the finished drink.

Active compounds and evidence

Because kombucha is a fermented, tea-based drink, it inherits some of tea’s polyphenol content along with organic acids and live microbes from fermentation. Marketing often extends this into broad “detox” and gut-health claims; the direct human evidence for kombucha specifically remains sparse, consisting mostly of small studies, case reports, and extrapolation from general fermented-food and probiotic research rather than large randomized trials of kombucha itself. It’s reasonable to treat kombucha as one of several fermented foods that may support dietary variety, without over-claiming specific clinical outcomes.

Safety and contraindications

Trace alcohol: Commercial kombucha in the U.S. is generally kept under 0.5% ABV to be sold as a non-alcoholic beverage, but homemade or “hard” kombucha can contain meaningfully more; check labels if avoiding alcohol.
Homemade fermentation risk: Improperly maintained cultures or non-sterile equipment can allow harmful bacteria or mold to grow; the FDA and CDC have documented illness linked to home-brewed kombucha.
Excess acidity: Case reports exist of acidosis and other adverse effects in immunocompromised individuals consuming large quantities of kombucha; moderate intake and commercially produced product are the safer default.
Pregnancy: Because of trace alcohol and live-culture content, many clinicians advise caution or avoidance during pregnancy.

How it’s typically prepared

Sweetened tea is fermented at room temperature with an active SCOBY for about 7–14 days (first fermentation), often followed by a bottled second fermentation with fruit to build carbonation and flavor.

Sources

Clinically reviewed by Dr. Shilpa Thakur. Last reviewed 2026-07-20. Educational information, not medical advice; consult a qualified clinician before regular use if pregnant, immunocompromised, or avoiding alcohol entirely.