Is Kombucha Good for Gut Health? What the Evidence Says

The verdict: kombucha may help a little, but the proof is thin

Kombucha is a fermented tea that carries live bacteria and yeasts, and a few small human studies suggest it may nudge the gut microbiome. But the evidence is early: as recently as 2019, a systematic review found just one human study of kombucha’s health effects. If you enjoy it, a modest daily glass can be part of a fermented-food habit. Don’t count on it to fix gut problems.

What the research shows

Very few human trials

Most of kombucha’s reputation comes from lab dishes and animal studies. When Kapp and Sumner searched the medical literature for their 2019 review in Annals of Epidemiology, they screened 310 articles and found only one that reported health results in people. A review of fermented foods the same year by Dimidi and colleagues (Nutrients, 2019) found no randomized trials of kombucha for gut health and no studies of how it affects the gut microbiome in animals or humans.

Newer microbiome studies are small and short

Since then, a few trials have looked directly at the gut. In a 2024 controlled study in Scientific Reports, 24 healthy adults eating a typical Western diet were randomized to kombucha (16 people) or a control (8 people) for four weeks. The researchers saw modest shifts in gut bacteria, including more of some species that make short-chain fatty acids, but no significant changes in inflammation markers or blood tests across the group. The study was funded by a kombucha company, and the authors note the small size and wide variation between people.

A 2025 Spanish trial randomized 60 healthy adults to drink 250 mL a day of either unfermented tea or a fiber-enriched kombucha for six weeks. The kombucha group had more Bifidobacterium afterward and a borderline drop in triglycerides. Because the drink had added fiber and the study was funded by its maker, it can’t tell us what ordinary kombucha does.

Blood sugar: one pilot study

A 2023 pilot crossover trial in 12 adults with type 2 diabetes found that average fasting blood sugar fell after four weeks of kombucha (from 164 to 116 mg/dL), while the change on placebo was not significant. The authors call it a pilot limited by its small size. The kombucha used also contained 1.5% alcohol, which is worth knowing if you avoid alcohol.

Fermented foods as a group

The strongest hint comes from a broader study. In a 10-week Stanford trial (Wastyk et al., Cell, 2021), 36 healthy adults ate either a high-fiber diet or a diet rich in fermented foods, including kombucha, yogurt, kefir and kimchi. The fermented-food group’s microbial diversity rose and 19 inflammatory proteins in the blood fell, according to Stanford Medicine. Kombucha was one food among many, so the study can’t isolate its effect.

Caveats to keep in mind

• Sugar: kombucha starts as sweet tea. Colorado State University’s Food Source Information puts unflavored kombucha at roughly 30 calories and 2 to 3 grams of sugar per 8 ounces, but juice-flavored bottles can carry more. The FDA’s Daily Value for added sugars is 50 grams a day.
• Alcohol: fermentation makes some alcohol. Federal rules treat kombucha that reaches 0.5% alcohol by volume or more at any point as an alcohol beverage, according to the Alcohol and Tobacco Tax and Trade Bureau.
• Home brewing risks: Mayo Clinic warns that kombucha brewed in unclean conditions can grow harmful germs, that it has caused stomach upset, infections and allergic reactions in some people, and that its acid can pull lead from glazed ceramic pots.
• Who should skip it: Mayo Clinic advises people who are pregnant, breastfeeding or have a weakened immune system to avoid kombucha. CSU adds young children and people with preexisting conditions.
• Caffeine and acid: CSU notes that kombucha has small amounts of caffeine from the tea, and fermentation makes it acidic. Either can bother a sensitive stomach.

How to choose and use kombucha

1. Pick refrigerated, unpasteurized bottles if live cultures are your goal. Heat-treated drinks may keep the flavor but not the microbes.
2. Read the sugar line. Compare added sugars per bottle, not per serving, since many bottles hold two servings.
3. Start small. CSU suggests new drinkers have no more than about 4 ounces a day at first, with plenty of water, to limit stomach discomfort.
4. Drink it with food if the acidity or fizz bothers you on an empty stomach.
5. If you brew at home, follow a tested method. The National Center for Home Food Preservation’s kombucha recipe calls for sanitized equipment, a starter liquid with a pH of 4.0 or less, and fermenting at 68 to 77°F for 7 to 10 days, then refrigerating and using within 30 days.
6. Mix up your ferments. Kombucha works best as one of several fermented foods, alongside options with stronger human research such as kefir and yogurt.

If you want brand-by-brand label details, see our comparison of the best kombucha for gut health.

Frequently Asked Questions

Related Topics

• Best Kombucha for Gut Health: brands compared by label.
• Probiotic Drinks: other drinks with live cultures.
• Gut Health Drinks: what is worth sipping and what isn’t.
• Fermented Foods for Gut Health: the wider family of ferments.
• Kefir Benefits: What the Evidence Shows: a fermented drink with more human research.

Sources

• Kapp JM, Sumner W. Kombucha: a systematic review of the empirical evidence of human health benefit (Annals of Epidemiology, 2019)
• Dimidi E, et al. Fermented Foods: Definitions and Characteristics, Impact on the Gut Microbiota and Effects on Gastrointestinal Health and Disease (Nutrients, 2019)
• Ecklu-Mensah G, et al. Modulating the human gut microbiome and health markers through kombucha consumption: a controlled clinical study (Scientific Reports, 2024)
• Arce-López B, et al. Effect of fiber-modified kombucha tea on gut microbiota in healthy population: A randomized controlled trial (RCT) (Current Research in Food Science, 2025)
• Mendelson C, et al. Kombucha tea as an anti-hyperglycemic agent in humans with diabetes – a randomized controlled pilot investigation (Frontiers in Nutrition, 2023)
• Wastyk HC, et al. Gut-microbiota-targeted diets modulate human immune status (Cell, 2021)
• Fermented-food diet increases microbiome diversity, decreases inflammatory proteins, study finds (Stanford Medicine, 2021)
• Kombucha tea: Does it have health benefits? (Mayo Clinic)
• Kombucha (Food Source Information, Colorado State University)
• Kombucha (Alcohol and Tobacco Tax and Trade Bureau)
• Added Sugars on the Nutrition Facts Label (U.S. Food and Drug Administration)
• Kombucha Tea (National Center for Home Food Preservation, University of Georgia)