Functional Foods · Fermented drink
Kombucha
Fermented Camellia sinensis tea · also called Fermented tea, kombucha tea
Kombucha is a fizzy, sour tea made by fermenting sweetened tea with bacteria and yeast. A few small human trials looked at blood sugar, cholesterol and gut bacteria, with mostly weak or mixed results, and many of the popular claims have no human evidence. The main cautions are alcohol that varies from bottle to bottle, caffeine, acid on teeth, lead from ceramic containers, and advice to avoid it in pregnancy and young children.
General information, not medical advice. Last substantive update · Not medically reviewed. A named clinician has not signed off on this page. How this page is made
About Kombucha
Kombucha is a fermented tea drink. It is a popular food, not a proven remedy: the human trials are few, small and short, and the safety points are better documented than the benefits.
What it is
Kombucha is a sparkling, sugared tea that is fermented for several days with a mix of bacteria and yeast, sometimes called a SCOBY. Yeast turn sugar into alcohol, and acetic acid bacteria then turn some of that alcohol into acetic acid, which makes it sour.
A 2022 review says kombucha drinking has been reported as early as 220 B.C. That is a historical report, not proof of benefit. The tea used is usually Camellia sinensis, the tea plant.
What is in it
No USDA record for plain kombucha could be read. A 2026 New Zealand study of the labels of 35 products found an average of 43.6 kJ per serving, about 10 kcal, and called it a low-energy drink. Sugars and carbohydrates varied most between products, so flavoured or juice-blended bottles can be quite different. Check the label.
Kombucha contains acetic and lactic acids (both under 1% in one trial product), phenolic compounds from the tea (145 identified in one black tea kombucha), caffeine, and live microbes in some products. Its make-up changes with sugar, time and temperature.
Alcohol and acid
Alcohol in kombucha varies a lot. In 684 samples in British Columbia it ranged from none detected to 3.62%, with a mean of 0.77%, and 31.5% were over the province's 1% limit for non-alcoholic drinks. In New Zealand 2 of 9 samples were over 1.15%. US TTB treats kombucha that reaches 0.5% at any point, even after bottling, as an alcohol beverage.
Kombucha is also acidic. Lab studies on teeth found it softened or etched enamel, sometimes as much as cola. These were not studies in people.
What the research shows
A 2019 systematic review of searches to 2018 found only one human study out of 310 articles. Since then a handful of small trials have appeared, 11 to 90 people each, lasting a single meal to 12 weeks. Several were funded by or linked to kombucha makers, and each used a different kombucha.
The strongest-looking results are for blood sugar, but those are two very small trials. In the best-designed trial of cholesterol markers, the kombucha and control groups did not differ significantly. Gut bacteria shifted in some trials, but no trial showed that this helped health. For detox, cancer or arthritis claims, no human evidence was found.
Kombucha, fermented foods and probiotics
An expert panel (ISAPP) defines fermented foods as foods made through desired microbial growth and enzymatic conversions of food components, and keeps them separate from probiotics. Whether a bottle has live microbes depends on the product. Results for one do not transfer to the other.
At a glance
Traditional uses history, not proof
- Drunk for a long time as a fermented tea; reported as early as 220 B.C.
- Long use is not proof that it treats any condition
Studied for research
- Blood sugar, very low certainty (two tiny trials)
- Cholesterol, triglycerides and related markers, very low certainty
- Gut bacteria, low certainty for the change, no proven health benefit
- Gut symptoms, very low certainty
- Immune and antioxidant markers, insufficient evidence
- Detox, cancer, arthritis: no human evidence found
Main compounds
- Acetic and lactic acids
- Phenolic compounds from tea
- Caffeine
- Alcohol (ethanol)
- Live microbes in some products
Common forms
- Commercial kombucha as studied in trials (green tea, black tea, fibre-enriched)
- Home-brewed kombucha: no methods given here, and the risks are described on the safety tab
- Probiotic supplements are a different product and are not covered
Research links: 2019 systematic review of human evidence · 2023 trial: kombucha and blood sugar in type 2 diabetes · US TTB: kombucha and alcohol · Research Library · Genes & Biomarkers Library
What it is and its history
- Accepted scientific name
- Kombucha (a fermented tea drink, not a single species)
- Common names
- Kombucha (English); Fermented tea (English); Kombucha (Spanish)
- Family or group
- The tea plant is in the Theaceae family (GBIF). Kombucha is a fermented drink made from tea, sugar and a microbial culture.
- Classification
- Plantae (tea plant) > Tracheophyta > Magnoliopsida > Ericales > Theaceae > Camellia > Camellia sinensis
- Native range
- Not verified from a source read.
- What it looks like
- Leaves: Made from a tea infusion; tea leaf details were not researched.
- Harvest and processing
- A sugared tea is fermented for several days at ambient temperature using a cellulose pellicle of acetic acid bacteria and yeast. Yeast turn sugar into fructose and glucose, then ethanol; acetic acid bacteria turn ethanol into acetic acid, which makes it sour. Sugar type and amount, time and temperature change the acids, vitamins, phenolics and alcohol (de Miranda 2022). Home-brewing methods are not given here.
- Look-alikes and adulterants
- Name: Water kefir; Note: Another fermented, fizzy drink made with a different culture; a separate page.; Name: Unfermented iced tea or tea with probiotic added; Note: Not the same: no fermentation, different acids and alcohol.; Name: Kvass; Note: A fermented drink made from bread or grain; a separate page.
Traditional use and history history, not clinical proof
| Tradition or era | Documented use | Source |
|---|---|---|
| Reported from about 220 B.C. | A 2022 review says consumption of kombucha has been reported as early as 220 B.C. This is a historical report, not evidence of benefit. | Wang et al. 2022 (PMID 36360067), abstract read |
Traditional use shows how it was used. It does not show that it works or is safe today.
What is inside, and how it may work
What it contains and how those compounds act in cells and animals. Laboratory and animal mechanisms are not proven effects in people.
Main compounds
| Compound | Family | Where it is concentrated | Activity studied | Level of evidence |
|---|---|---|---|---|
| Ethanol (alcohol) | alcohol | Whole drink Mean 0.77% alcohol by volume, none detected to 3.62% in 684 BC samples; 0.68% (Alcolyzer) in 9 NZ samples; 1.5% in the diabetes trial product | Made by yeast from sugar and partly turned into acetic acid. Level varies with sugar, time, temperature and storage. 12 18 16 24 | Measured |
| Acetic and lactic acids | organic acids | Whole drink Both under 1% in the product tested in the diabetes trial | Give the sour taste and low pH (2.82 to 3.66 in 7 commercial kombuchas). 16 24 14 | Measured |
| Phenolic compounds (flavonoids and phenolic acids) | polyphenols | From the tea 145 phenolic compounds identified in a black tea kombucha (81% flavonoids, 19% phenolic acids) | Described as the main bioactive group in reviews. Not shown to matter for health in people. 6 19 | Measured lab |
| Caffeine | alkaloid | From the tea 114 mg/L in the lowest of four lab-brewed green tea batches; other batches higher; no shop-bought figure read | A stimulant also found in tea and coffee. 9 27 | Measured lab |
| Sugars | carbohydrate | Left after fermentation or added Not read for typical products; label sugar and carbohydrate varied most between 35 New Zealand products | Starting sugar is what yeast ferment, so more sugar can mean more alcohol and more sugar left. 18 | Label survey |
| Live microbes | microbes | Culture About a million colony-forming units per mL of each group (lactic, acetic acid bacteria and yeast) in the diabetes trial product | Whether a bottle has live microbes depends on the product; ISAPP separates fermented foods from probiotics. 16 15 | Measured |
Mechanisms, receptors and pathways
| Target or pathway | Gene or receptor | What was found | Level |
|---|---|---|---|
| Fermentation chemistry | Not applicable | Yeast change sugar to ethanol and acetic acid bacteria change ethanol to acetic acid, lowering pH. 24 | Lab |
| Possible effects on blood sugar | Not specified | The diabetes trial authors said animal results led them to test kombucha in people. No mechanism in people was shown. 16 | Animal hypothesis |
| Gut bacteria | Not applicable | Trials found some kombucha-linked bacteria and some changes in stool bacteria; no link to a health outcome was shown. 7 6 2 | Human observation |
Absorption, metabolism and elimination
- Absorption
- Not found for kombucha.
- Distribution
- Not found.
- Metabolism
- Not found.
- Elimination
- Not found.
- Bioavailability
- Not established.
Isolated compounds versus whole extracts
Every human result on this page is for kombucha drinks, but the drinks differ (green tea, black tea, fibre-enriched, with or without grape skin extract), so one result does not carry over to every bottle. Probiotic supplements are a different product; ISAPP separates fermented foods from probiotics.
Nutritional composition
No USDA FoodData Central record for plain kombucha could be read: the public data service was rate-limited, and web results were from third-party sites that were not trusted. What was read: a 2026 New Zealand study of the labels of 35 kombucha products from 9 companies found an average of 43.6 kJ per serving (standard deviation 27.7), which is about 10 kcal, and called it a low-energy drink; sugars and carbohydrates varied most between products. The serving size is not given in the abstract. Vitamins, minerals and protein were not read. A flavoured or juice-blended bottle can be quite different, so use the label. Alcohol is covered on the safety tab.
1 low certainty3 very low certainty2 not enough evidence
What was looked at
The 6 benefits and uses checked for Kombucha, each with how strong the evidence is. Tap one to open it.
- Blood sugarVery low certainty
- Cholesterol, triglycerides and related markersVery low certainty
- Gut bacteria compositionLow certainty
- Gut symptoms and gut liningVery low certainty
- Immune cells and antioxidant markersNot enough evidence
- Detox, cancer, arthritis and other popular claimsNot enough evidence
Lab markers tracked in the studies
Fasting blood glucoseGlycaemic and insulin index after a mealTriglyceridesLDL cholesterolFasting insulin and HOMA-IRGut bacteria (stool sequencing)Neutrophils and lymphocytes
What is Kombucha good for?
The main studied uses and how strong the human evidence is for each. Every result is for a particular kombucha product, so it may not carry over to other bottles.
Benefits, one by one
Each card is a research question, not a promise. Tap a goal to filter. Open a card to see the studies, doses and limits.
Blood sugar
Very low certaintyTwo very small trials found lower blood sugar after kombucha: one over 4 weeks in 12 adults with type 2 diabetes, one after a single meal in 11 healthy adults. Both are tiny, and both have ties to the kombucha or probiotic field.
2 studiesCommercial or live kombucha drinks, as studied. Other bottles may dif…
Studies, doses and limits
What the trials found
In 12 adults with type 2 diabetes, fasting glucose fell from 164 to 116 mg/dL after 4 weeks of kombucha (p = 0.035); with placebo it went from 162 to 141 (p = 0.078). The two drinks were not compared head to head; each was compared with the person's own start. The kombucha tested had 1.5% alcohol. In 11 healthy adults, a high-glycaemic-index meal eaten with live kombucha had a glycaemic index of 68 versus 86 with soda water (p = 0.041), and an insulin index of 70 versus 85 (p = 0.041).
Results
A lower blood sugar reading in two tiny trials. The results need larger studies before anyone can say it is real or lasting.
Effect sizes as reported
Fasting glucose 164 to 116 mg/dL with kombucha (p = 0.035) versus 162 to 141 with placebo (p = 0.078), n = 12. Glycaemic index 68 versus 86, insulin index 70 versus 85, n = 11.
Why this rating
Very low: 12 and 11 people, one trial compared each person only with their own start, one covered a single meal in healthy people, and authors have industry ties. No larger or longer trial was read.
Form and dose studied
Commercial or live kombucha drinks, as studied. Other bottles may differ.
Who was studied
Adults with type 2 diabetes (one trial); healthy adults (one trial).
Limits
Very small samples; short; not the same product in each trial; the diabetes trial used a kombucha with 1.5% alcohol, which matters for people on diabetes medicines.
Why researchers looked
Animal studies suggested kombucha might lower blood sugar, so researchers tested it in people.
Traditional use
Kombucha has been drunk for a long time as a tea drink. Long use is not proof that it treats any condition.
Proposed mechanism Not established
Not shown in people. The 2023 diabetes trial authors say animal studies led to their idea; no mechanism was tested in the sources read.
A proposed mechanism does not show that the effect happens in people.
Kombucha can contain sugar and alcohol. People with diabetes should ask their care team before changing what they drink.
Cholesterol, triglycerides and related markers
Very low certaintyA green tea kombucha trial in 59 adults with excess weight found no clear difference between groups on cholesterol or other markers. A separate trial of a fibre-enriched kombucha found lower triglycerides compared with unfermented tea, and it was funded by a kombucha maker.
3 studiesGreen tea kombucha, fibre-enriched kombucha and a kombucha-based prod…
Studies, doses and limits
What the trials found
In 59 adults with excess weight on a diet cutting 500 kcal a day, adding 200 mL of green tea kombucha a day for 10 weeks lowered total cholesterol, LDL, VLDL, triglycerides and uric acid compared with the person's own start. Between the two groups, no marker differed significantly. Men in the kombucha group had a lower HbA1c than men in the control group (p = 0.010). In 60 healthy adults (58 finished), fibre-enriched kombucha for 6 weeks changed triglycerides differently from unfermented tea (p = 0.031); within the kombucha group the fall from 69.59 to 62.80 mg/dL was not significant (p = 0.053). In a 24-person trial, fasting insulin and HOMA-IR rose in the kombucha group.
Results
No clear benefit on cholesterol in the best-designed comparison. One funded trial of a modified product found a triglyceride difference. One small trial saw insulin markers go the other way.
Effect sizes as reported
Group comparison: no significant difference for any marker (n = 59). Triglycerides between groups p = 0.031 (fibre-enriched kombucha, n = 60). Fasting insulin and HOMA-IR increased within the kombucha group (n = 24).
Why this rating
Very low: the main comparison between groups was not significant, results that were significant were within one group only, trials were small and short, one was funded by a kombucha maker and tested a modified product, and one small trial pointed the other way.
Form and dose studied
Green tea kombucha, fibre-enriched kombucha and a kombucha-based product; each differs.
Who was studied
Adults with excess weight; healthy adults.
Limits
The weight-loss diet may explain the changes seen within the kombucha group. The kombucha was not compared with other drinks in most trials.
Why researchers looked
Kombucha is marketed as a healthy drink, so trials looked at blood fats and related markers.
Traditional use
Kombucha has been drunk for a long time as a tea drink. Long use is not proof that it treats any condition.
Proposed mechanism Not established
Not established. No mechanism was tested in the abstracts read.
A proposed mechanism does not show that the effect happens in people.
None specific beyond the alcohol, caffeine and acid points on the safety tab.
Gut bacteria composition
Low certaintyFour small trials looked at gut bacteria. Some kombucha-linked bacteria were found in drinkers' stool and a few groups changed, but nobody measured whether this helped health.
4 studiesBlack tea, green tea and fibre-enriched kombucha.
Studies, doses and limits
What the trials found
In 24 healthy adults, a kombucha-linked bacterium (Weizmannia) and some bacteria that make short-chain fatty acids were more abundant at the end of 4 weeks. In 46 adults with and without obesity, 8 weeks of black tea kombucha with no comparison group raised Subdoligranulum in the obesity group (P = 0.031) and lowered Ruminococcus and Dorea. In 60 healthy adults, fibre-enriched kombucha raised Bifidobacterium and lowered Ruminococcus torques compared with the start. In 59 adults with excess weight, green tea kombucha did not significantly change gut bacteria compared with the control group.
Results
Some shifts in gut bacteria in three trials, none in a fourth. No trial showed that the shifts helped health.
Effect sizes as reported
Changes in relative abundance of named bacteria; no health outcome attached.
Why this rating
Low for the finding that some bacteria change (several small trials, but one without a control group and one negative). Insufficient for any health benefit.
Form and dose studied
Black tea, green tea and fibre-enriched kombucha.
Who was studied
Healthy adults; adults with excess weight or obesity.
Limits
Small trials, mostly 8 weeks or less; stool bacteria differ a lot between people; one trial had no control group; two were funded by or linked to kombucha makers.
Why researchers looked
Kombucha is a fermented drink with live microbes, so researchers asked whether it changes gut bacteria.
Traditional use
Kombucha has been drunk for a long time as a tea drink. Long use is not proof that it treats any condition.
Proposed mechanism Not established
Not established. The trials counted bacteria in stool; none showed how any change would help health.
A proposed mechanism does not show that the effect happens in people.
None specific.
Gut symptoms and gut lining
Very low certaintyOne trial in 59 adults with excess weight found that those who drank green tea kombucha reported fewer gut-motility symptoms than controls. It found no difference in gut lining leakiness between groups.
1 studiesGreen tea kombucha.
Studies, doses and limits
What the trials found
In the 10-week trial, green tea kombucha did not significantly change gut permeability (measured by urine lactulose/mannitol, plasma zonulin and LPS-binding protein) compared with the control group. Only the control group had rises in stool pH, the lactulose/mannitol ratio and zonulin. The kombucha group reported fewer gut-motility symptoms than the control group.
Results
Fewer self-reported motility symptoms in one trial; no clear difference in gut lining tests.
Effect sizes as reported
Symptom scores favoured kombucha; permeability markers not significantly different between groups.
Why this rating
Very low: one trial, 59 people, self-reported symptoms, in people also on a weight-loss diet.
Form and dose studied
Green tea kombucha.
Who was studied
Adults with excess weight on a calorie-cut diet.
Limits
One trial; symptoms were reported by the participants; no trial in people with a gut disease was read.
Why researchers looked
People take kombucha hoping for better digestion.
Traditional use
Kombucha has been drunk for a long time as a tea drink. Long use is not proof that it treats any condition.
Proposed mechanism Not established
Not established.
A proposed mechanism does not show that the effect happens in people.
None specific.
Immune cells and antioxidant markers
Not enough evidenceA 12-week trial in 90 healthy beginner runners found no change in the main antioxidant marker. Immune cell counts changed a little, which the authors call exploratory.
1 studiesGreen tea kombucha.
Studies, doses and limits
What the trials found
In 90 healthy adults aged 18 to 45, 12 weeks of green tea kombucha did not significantly change ferric reducing antioxidant power (the main outcome), or acute immune and oxidative responses to exercise. Over the weeks the kombucha group had more neutrophils (p = 0.026) and fewer lymphocytes (p = 0.023) than the other groups. After adjusting for multiple testing the authors call these findings exploratory. Grape skin extract added nothing.
Results
No change in the main outcome. Small changes in two immune cell counts that may be chance.
Effect sizes as reported
Primary outcome (FRAP): no significant change. Neutrophils p = 0.026 and lymphocytes p = 0.023, exploratory.
Why this rating
Insufficient: one trial in a narrow group; the main outcome was null and the other findings are exploratory.
Form and dose studied
Green tea kombucha.
Who was studied
Healthy adults starting a running programme.
Limits
One trial; narrow population; counts of immune cells are not the same as fewer infections, which was not measured.
Why researchers looked
Kombucha is marketed as an antioxidant drink.
Traditional use
Kombucha has been drunk for a long time as a tea drink. Long use is not proof that it treats any condition.
Proposed mechanism Not established
Not established.
A proposed mechanism does not show that the effect happens in people.
None specific.
Detox, cancer, arthritis and other popular claims
Not enough evidenceNo human study supporting these claims was found. Poison Control says there are no scientific studies to support the many health claims; reviews say the benefits reported come from lab and animal work.
3 studiesKombucha.
Studies, doses and limits
What the trials found
A 2019 systematic review searched PubMed, Scopus and Ovid in July 2018 (310 articles) and found one human study with empirical results. A 2022 review says the antioxidant, antimicrobial, antidiabetic and anticancer effects attributed to kombucha still need clinical studies. Poison Control (a public health information page) says there are no scientific studies to support the many health claims.
Results
No human evidence for detox, cancer or arthritis claims. The 2018 search is older than the trials listed on this page.
Why this rating
Insufficient: reviews found no human trials for these uses; lab and animal results are not evidence in people.
Form and dose studied
Kombucha.
Limits
The 2019 review predates recent trials; none of the newer trials looked at these claims.
Why researchers looked
Many claims for kombucha circulate online.
Traditional use
Kombucha has been drunk for a long time as a tea drink. Long use is not proof that it treats any condition.
Proposed mechanism Lab and animal
Lab and animal studies describe antioxidant and antimicrobial activity of kombucha compounds; this was not shown to matter in people.
A proposed mechanism does not show that the effect happens in people.
Using kombucha in place of care for a serious illness could cause harm. Ask a clinician.
Connections to the rest of health
How Kombucha connects to the rest of our health knowledge graph. Every link says what kind of connection it is. A safety link (for example to the liver) is a warning, not a benefit. A study that merely mentions a topic never creates a benefit link.
Explore every connection: goals, body systems, organs, symptoms, genes
A. Wellness goals
| Connected to | Kind of connection | Evidence status | Context | Studies |
|---|---|---|---|---|
| Blood Sugar Balance | Very low certainty | Blood sugar: Two very small trials found lower blood sugar after kombucha: one over 4 weeks in 12 adults with type 2 diabetes, one after a single meal in 11 healthy adults. Both are tiny, and both have ties to the kombucha or probiotic field. | 16 3 | |
| Cholesterol Balance | Very low certainty | Cholesterol, triglycerides and related markers: A green tea kombucha trial in 59 adults with excess weight found no clear difference between groups on cholesterol or other markers. A separate trial of a fibre-enriched kombucha found lower triglycerides compared with unfermented tea, and it was funded by a kombucha maker. | 4 2 7 | |
| Heart Health | Very low certainty | Cholesterol, triglycerides and related markers: A green tea kombucha trial in 59 adults with excess weight found no clear difference between groups on cholesterol or other markers. A separate trial of a fibre-enriched kombucha found lower triglycerides compared with unfermented tea, and it was funded by a kombucha maker. | 4 2 7 | |
| Healthy Weight | Very low certainty | Cholesterol, triglycerides and related markers: A green tea kombucha trial in 59 adults with excess weight found no clear difference between groups on cholesterol or other markers. A separate trial of a fibre-enriched kombucha found lower triglycerides compared with unfermented tea, and it was funded by a kombucha maker. | 4 2 7 | |
| Gut Digestive Health | Low certainty | Gut bacteria composition: Four small trials looked at gut bacteria. Some kombucha-linked bacteria were found in drinkers' stool and a few groups changed, but nobody measured whether this helped health. | 7 6 2 8 | |
| Gut Digestive Health | Very low certainty | Gut symptoms and gut lining: One trial in 59 adults with excess weight found that those who drank green tea kombucha reported fewer gut-motility symptoms than controls. It found no difference in gut lining leakiness between groups. | 8 | |
| Immune Wellness | Not enough evidence | Immune cells and antioxidant markers: A 12-week trial in 90 healthy beginner runners found no change in the main antioxidant marker. Immune cell counts changed a little, which the authors call exploratory. | 5 | |
| Preventive Wellness | Not enough evidence | Detox, cancer, arthritis and other popular claims: No human study supporting these claims was found. Poison Control says there are no scientific studies to support the many health claims; reviews say the benefits reported come from lab and animal work. | 13 25 29 |
B. Body systems
| Connected to | Kind of connection | Evidence status | Context | Studies |
|---|---|---|---|---|
| Endocrine System | Biological association | Very low certainty | Studied for: Blood sugar | 16 3 |
| Metabolic System | Biological association | Very low certainty | Studied for: Blood sugar Studied for: Cholesterol, triglycerides and related markers | 16 3 4 2 7 |
| Cardiovascular System | Biological association | Very low certainty | Studied for: Cholesterol, triglycerides and related markers | 4 2 7 |
| Digestive System | Biological association | Low certainty | Studied for: Gut bacteria composition Studied for: Gut symptoms and gut lining | 7 6 2 8 |
| Gut Microbiome | Biological association | Low certainty | Studied for: Gut bacteria composition | 7 6 2 8 |
| Immune System | Biological association | Not enough evidence | Studied for: Immune cells and antioxidant markers | 5 |
| Whole Body | Biological association | Not enough evidence | Studied for: Detox, cancer, arthritis and other popular claims | 13 25 29 |
E. Health conditions
| Connected to | Kind of connection | Evidence status | Context | Studies |
|---|---|---|---|---|
| Lead poisoning | Adverse effect or risk | Documented risk | Case reports and an outbreak investigation tie lead poisoning to ceramic containers. Lead poisoning followed kombucha brewed or stored in ceramic containers. Preparation or compound: Kombucha brewed or stored in ceramic containers |
20 17 |
| Lactic acidosis | Adverse effect or risk | Case reports | Case reports link kombucha with lactic acidosis; cause not proven. Preparation or compound: Kombucha tea |
11 26 |
| Dental erosion | Adverse effect or risk | Laboratory | Lab studies show enamel softening or etching. Preparation or compound: Acidic kombucha |
14 21 22 |
I. Biomarkers
| Connected to | Kind of connection | Evidence status | Context | Studies |
|---|---|---|---|---|
| Fasting blood glucose | Biological association | Very low certainty | Measured in trials: lowered. A lab change is not the same as a health benefit. | 16 |
| Glycaemic and insulin index after a meal | Biological association | Very low certainty | Measured in trials: lowered. A lab change is not the same as a health benefit. | 3 |
| Triglycerides | Biological association | Very low certainty | Measured in trials: lowered. A lab change is not the same as a health benefit. | 2 4 |
| LDL cholesterol | Biological association | Very low certainty | Measured in trials: no clear change between groups. A lab change is not the same as a health benefit. | 4 |
| Fasting insulin and HOMA-IR | Biological association | Very low certainty | Measured in trials: raised (within the kombucha group). A lab change is not the same as a health benefit. | 7 |
| Gut bacteria (stool sequencing) | Biological association | Low certainty | Measured in trials: some groups changed. A lab change is not the same as a health benefit. | 7 6 2 8 |
| Neutrophils and lymphocytes | Biological association | Not enough evidence | Measured in trials: exploratory shifts. A lab change is not the same as a health benefit. | 5 |
K. Biological pathways
| Connected to | Kind of connection | Evidence status | Context | Studies |
|---|---|---|---|---|
| Ethanol | Preliminary mechanism | Measured | Present in kombucha at variable levels. | 12 18 |
| Caffeine | Preliminary mechanism | Measured lab | Present because kombucha is made from tea. | 9 |
| Gut microbiome | Preliminary mechanism | Human | Small trials saw some bacteria shift; health effect unknown. | 7 6 2 8 |
L. Active compounds
| Connected to | Kind of connection | Evidence status | Context | Studies |
|---|---|---|---|---|
| Ethanol (alcohol) | Biological association | Measured | Made by yeast from sugar and partly turned into acetic acid. Level varies with sugar, time, temperature and storage. Preparation or compound: Whole drink |
12 18 16 24 |
| Acetic and lactic acids | Biological association | Measured | Give the sour taste and low pH (2.82 to 3.66 in 7 commercial kombuchas). Preparation or compound: Whole drink |
16 24 14 |
| Phenolic compounds (flavonoids and phenolic acids) | Biological association | Measured lab | Described as the main bioactive group in reviews. Not shown to matter for health in people. Preparation or compound: From the tea |
6 19 |
| Caffeine | Biological association | Measured lab | A stimulant also found in tea and coffee. Preparation or compound: From the tea |
9 27 |
| Sugars | Biological association | Label survey | Starting sugar is what yeast ferment, so more sugar can mean more alcohol and more sugar left. Preparation or compound: Left after fermentation or added |
18 |
| Live microbes | Biological association | Measured | Whether a bottle has live microbes depends on the product; ISAPP separates fermented foods from probiotics. Preparation or compound: Culture |
16 15 |
Each connection is stored with the ingredient, the connected record, the kind of connection, the evidence status, the supporting studies, the preparation or compound involved, and a review date (last reviewed October 26, 2026).
The evidence
The research centre for Kombucha. Every record here was checked against PubMed or the publisher's page; we never list a study we have not verified.
Evidence by outcome
Bars show how many studies we found for each outcome, not how well it works. People are added up across trials only (reviews are not added, to avoid double counting).
How we rate evidence
High certainty
Several well-run trials or reviews agree; further research is unlikely to change the picture much.
Moderate certainty
Good trials point the same way, but some doubt remains.
Low certainty
Small, short or inconsistent trials. The finding could change with better research.
Very low certainty
Very little or very weak human data. Treat as a possibility only.
Mixed findings
Trials or reviews disagree with each other.
Not enough evidence
Not enough human research to say either way.
Evidence against
Good research found no benefit, or found harm.
We take the reviewers' own risk-of-bias and GRADE statements where they exist, and otherwise judge from study size, design, consistency, directness and whether a product matches what is sold. Many publications do not make evidence high. Method note: We started from our earlier kombucha page, re-read every PubMed abstract listed, and read the pages of TTB, CDC, FDA and Poison Control. Only abstracts were read for studies. Items we could not verify are flagged in the research gaps.
Study library: every study we checked 30
| Study | Design | People | Product, dose, length | Result |
|---|---|---|---|---|
| Albaseer 2026 Ethical dilemmas in food labeling: the undisclosed presence of alcohol and its impact on vulnerable consumers. Rocz Panstw Zakl Hig · PMID 42466785 · DOI |
Narrative review |
Review of ethanol in foods including baked goods, kombucha and soy sauce | Foods and drinks that contain ethanol Food |
Says ethanol content in these products, kombucha among them, varies widely and can matter for children, pregnant women, people with alcohol use disorders and people with certain health conditions. Labelling of low-alcohol and non-alcoholic drinks differs between regions. Methods, limits and fundingOutcomes: Ethanol content and labelling Read: |
| Arce-Lopez 2025 Effect of fiber-modified kombucha tea on gut microbiota in healthy population: A randomized controlled trial (RCT). Curr Res Food Sci · PMID 40689297 · DOI |
Randomised double blind parallel |
60 Healthy adults (58 finished) |
Fibre-enriched kombucha tea (a modified product, not plain kombucha) Drink 250 mL per day (study design) 6 weeks · vs Unfermented tea |
Triglycerides differed between groups (p = 0.031); in the kombucha group they went from 69.59 to 62.80 mg/dL (p = 0.053, not significant). Bifidobacterium rose and Ruminococcus torques fell with kombucha. Authors call it promising and say more trials are needed. Funded by Komvida Kombucha, a kombucha maker. Methods, limits and fundingOutcomes: Blood chemistry, gut bacteria (16S sequencing) Registration: NCT06626997 Read: |
| Atkinson 2023 Glycemic index and insulin index after a standard carbohydrate meal consumed with live kombucha: A randomised, placebo-controlled, crossover trial. Front Nutr · PMID 36875857 · DOI |
Randomised crossover |
11 11 healthy adults |
Unpasteurised (live) kombucha taken with a high-glycaemic-index meal Drink Test drink with a single meal Single meals · vs Soda water (control) and diet lemonade |
Glycaemic index was 68 with kombucha versus 86 with soda water (p = 0.041); insulin index was 70 versus 85 (p = 0.041). Diet lemonade did not differ from soda water. Single meal, healthy adults. One author is a consultant to a kombucha company and co-owner of a firm selling wellness tonics based on it, and was involved in design and writing but not in data collection or analysis. Methods, limits and fundingOutcomes: 2-hour blood glucose and insulin response (glycaemic index, insulin index) Registration: ANZCTR 12620000460909 Read: |
| Bonifacio 2026 Effect of Green Tea Kombucha Within an Energy-Restricted Diet on Cardiometabolic Risk Markers in Individuals With Excess Body Weight: A Randomized Controlled Trial. J Food Sci · PMID 41957662 · DOI |
Randomised controlled |
59 Adults with excess body weight (BMI above 27) |
Green tea kombucha Drink 200 mL per day (study design) 10 weeks · vs Same energy-restricted diet (-500 kcal a day) without kombucha |
Within the kombucha group, total cholesterol (p = 0.024), LDL (p = 0.035), VLDL (p = 0.011), triglycerides (p = 0.012) and uric acid (p = 0.027) were lower than at the start. Comparing the two groups in the whole sample, no marker differed significantly (p > 0.05). Men in the kombucha group had lower HbA1c than men in the control group (p = 0.010). The control group's HbA1c rose within normal values. No conflicts reported. Methods, limits and fundingOutcomes: Cholesterol, triglycerides, uric acid, blood sugar markers Read: |
| Bonifacio 2026 Acute and Chronic Effects of Green Tea Kombucha With and Without Grape Skin Extract on Immune and Oxidative Stress Markers in Beginner Runners: A Randomized Controlled Trial. J Food Sci · PMID 42799570 · DOI |
Randomised controlled |
90 Healthy adults aged 18 to 45 starting a running programme |
Green tea kombucha, with and without grape skin extract Drink Not given in abstract 12 weeks · vs Control group |
No significant change in the main outcome (FRAP) and no change in acute immune or oxidative responses to exercise (p > 0.05). Over the weeks the kombucha group had more neutrophils (p = 0.026) and fewer lymphocytes (p = 0.023) than the other groups. After adjusting for multiple testing the authors call these findings exploratory. No extra effect from the grape skin extract. No conflicts reported. Methods, limits and fundingOutcomes: FRAP (an antioxidant-capacity marker), immune cell counts, exercise-related oxidative markers Read: |
| Costa 2025 Regular Consumption of Black Tea Kombucha Modulates the Gut Microbiota in Individuals with and without Obesity. J Nutr · PMID 39732435 · DOI |
Pre post no control |
46 23 normal-weight and 23 adults with obesity |
Black tea kombucha Drink Not given in abstract 8 weeks |
Kombucha-linked bacteria increased. Subdoligranulum (a butyrate producer) rose in the obesity group (P = 0.031); Ruminococcus and Dorea, higher at the start in that group, fell. Fungal diversity increased. These are changes in microbe counts; no health benefit was measured. No comparison group. Authors report no conflicts. Methods, limits and fundingOutcomes: Gut bacteria and fungi, urine and blood samples Registration: RBR-9832wsx (ReBEC) Read: |
| Ecklu-Mensah 2024 Modulating the human gut microbiome and health markers through kombucha consumption: a controlled clinical study. Sci Rep · PMID 39738315 · DOI |
Randomised controlled small |
24 Healthy adults eating a Western diet (kombucha n = 16, control n = 8) |
Kombucha drink Drink Not given in abstract 4 weeks of kombucha inside an 8-week trial · vs Control group |
No significant change in blood chemistry or inflammation markers across the whole group. Within the kombucha group fasting insulin and HOMA-IR (an insulin resistance score) rose; in the control group HDL cholesterol fell. A kombucha-linked bacterium (Weizmannia) and some bacteria that make short-chain fatty acids were more abundant in drinkers at the end. Authors say effects were modest and the sample small. Funded by GT's Living Foods, a kombucha maker, which was not involved in analysis. Methods, limits and fundingOutcomes: Stool microbiome, blood biochemistry, inflammation markers Registration: NA (not stated in abstract) Read: |
| Fraiz 2024 The Impact of Green Tea Kombucha on the Intestinal Health, Gut Microbiota, and Serum Metabolome of Individuals with Excess Body Weight in a Weight Loss Intervention: A Randomized Controlled Trial. Foods · PMID 39594049 · DOI |
Randomised controlled |
59 Adults with excess body weight on an energy-restricted diet (control 29, kombucha 30) |
Green tea kombucha Drink 200 mL per day (study design) 10 weeks · vs Same diet without kombucha |
No difference between groups in gut permeability or gut bacteria. Only the control group had rises in stool pH, the lactulose/mannitol ratio and zonulin. The kombucha group reported fewer gut-motility symptoms than the control group. Authors say green tea kombucha did not significantly improve microbiota or gut permeability. No conflicts reported. Methods, limits and fundingOutcomes: Gut permeability, gut bacteria, serum metabolites, gut symptoms Read: |
| Gantner 2025 Influence of Herbal Additives on the Physicochemical, Microbiological, Polyphenolic, and Sensory Profile of Green Tea-Based Kombucha. Foods · PMID 41154033 · DOI |
Laboratory study |
Four brewed laboratory batches | Green tea kombucha, plain and with mint, hibiscus or butterfly pea flower Drink 4 days of fermentation · vs Plain green tea kombucha |
The mint batch had the lowest caffeine of the four (114 mg/L), so the other batches had more; the abstract gives no figures for them. All samples were microbiologically safe by the tests used. A lab batch study, not a measure of shop-bought kombucha. Methods, limits and fundingOutcomes: Acids, polyphenols, caffeine, microbes, taste Read: |
| Gedela 2016 A Case of Hepatotoxicity Related to Kombucha Tea Consumption. S D Med · PMID 26882579 |
Case report |
1 One patient (details not in the abstract) |
Kombucha tea Drink Not in abstract Not in abstract |
The PubMed record shows only background text: a few case reports suggest kombucha may pose life-threatening or other adverse effects. The details of the case were not available in the abstract and were not read. Methods, limits and fundingOutcomes: Liver injury Read: |
| Holbourn 2017 Kombucha: is a cup of tea good for you? BMJ Case Rep · PMID 29197835 · DOI |
Case report |
1 One 54-year-old woman with asthma |
Kombucha tea Drink 10 days of symptoms |
Severe metabolic lactic acidosis in a woman who drank kombucha tea, which has been linked to lactic acidosis. She recovered fully with supportive care and by stopping the tea. A case report cannot show cause. Methods, limits and fundingOutcomes: Breathlessness with metabolic lactic acidosis Read: |
| Jang 2021 Ethanol Concentration of Kombucha Teas in British Columbia, Canada. J Food Prot · PMID 34143179 · DOI |
Product survey |
684 684 kombucha samples from processors and retail venues in British Columbia |
Commercial kombucha Drink |
Mean ethanol 0.77% and median 0.62% ABV, from not detectable up to 3.62%. Four teas (0.6%) made by BC processors were over 3% ABV, and 31.5% of samples were above the BC limit of 1% ABV for non-alcoholic drinks. BC-made kombucha had higher alcohol. The authors say this matters for pregnant women and young children. Methods, limits and fundingOutcomes: Ethanol content (percent alcohol by volume, ABV) Read: |
| Kapp 2019 Kombucha: a systematic review of the empirical evidence of human health benefit. Ann Epidemiol · PMID 30527803 · DOI |
Systematic review |
Search of PubMed, Scopus and Ovid in July 2018; 310 articles reviewed | Kombucha Drink |
Only one study with empirical results in people was found. Nothing turned up in research grant or trial registries. The authors say the many benefits claimed in non-human literature need testing in human trials. This search is from 2018, before the trials listed on this page. Methods, limits and fundingOutcomes: Human studies of health benefit Read: |
| Lind 2023 Erosive potential of ice tea beverages and kombuchas. Acta Odontol Scand · PMID 37192014 · DOI |
Laboratory study |
7 commercial kombuchas and 18 tea drinks tested in the lab | Commercial kombucha Drink · vs Cola (positive control), water (negative) |
Kombucha pH was 2.82 to 3.66 (cola 2.48 to 2.54). Calcium release was 198 to 746 mg/L for kombucha versus 57.7 to 71.9 for cola. Enamel etching was seen under the microscope. The authors conclude kombuchas especially have considerable erosive potential. Lab study, not in people. Methods, limits and fundingOutcomes: pH, fluoride, calcium released from tooth-mineral grains, enamel etching Read: |
| Marco 2021 The International Scientific Association for Probiotics and Prebiotics (ISAPP) consensus statement on fermented foods. Nat Rev Gastroenterol Hepatol · PMID 33398112 · DOI |
Expert consensus statement |
Expert panel convened in 2019 | Fermented foods and beverages in general Food |
Defines fermented foods and drinks as foods made through desired microbial growth and enzymatic conversions of food components, and separates them from probiotics. Covers safety, risks and possible benefits for fermented foods in general, not kombucha specifically. Several panel members report industry ties. Methods, limits and fundingOutcomes: Definition of fermented foods; link to probiotics Read: |
| Mendelson 2023 Kombucha tea as an anti-hyperglycemic agent in humans with diabetes - a randomized controlled pilot investigation. Front Nutr · PMID 37588049 · DOI |
Randomised crossover pilot |
12 Adults with type 2 diabetes |
A commercial kombucha product (tea fermented with bacteria and yeast; ethanol 1.5%) Drink 240 mL per day (study design) 4 weeks each, 8-week washout · vs Placebo drink |
Fasting glucose fell from 164 to 116 mg/dL after 4 weeks of kombucha (p = 0.035); with placebo it went from 162 to 141 (p = 0.078). Changes were tested against each person's own start, not directly between kombucha and placebo. Authors call the sample small and ask for larger studies. Drinks were donated by Craft Kombucha, which had no access to the data; two authors list ties to a probiotic company (Synbiotic Health). Methods, limits and fundingOutcomes: Fasting blood glucose, questionnaire outcomes, kombucha microbes Registration: NCT04107207 Read: |
| Munilla Garcia 2023 Brote familiar de saturnismo asociado al consumo de kombucha fabricada y comercializada en envases ceramicos. Rev Esp Salud Publica · PMID 37226984 |
Outbreak investigation |
A family lead poisoning outbreak in the Balearic Islands, Spain | Kombucha fermented and sold in ceramic containers Drink |
High blood lead was found in affected people. Lead in the kombucha was 0.95 mg/kg (unpackaged, 14 days), 7.1 mg/kg (unpackaged, 19 days) and 47 mg/kg (packaged, ready to drink). Lead leaching from the containers was 5.8 to 73 mg/L. The ceramic containers were named as the source. Spanish-language paper with an English abstract. Methods, limits and fundingOutcomes: Blood lead, lead in kombucha and containers Read: |
| Nordstrom 2026 Comparing Alcolyzer and GC-FID for Ethanol Measurement in Kombucha: Insights From Nutritional Labeling and Brewer Practices in New Zealand. J Food Sci · PMID 41536259 · DOI |
Product survey |
9 9 commercial kombucha samples for alcohol; labels of 35 products from 9 companies for nutrition |
Commercial kombucha Drink |
Mean alcohol 0.68% ABV (Alcolyzer) and 0.56% (GC-FID). 22% of samples (2 of 9) were over New Zealand's 1.15% ABV limit for non-alcoholic drinks. Label data (35 products) showed a low-energy drink at 43.6 kJ per serving on average (SD 27.7), with sugars and carbohydrates varying most between products. Brewers named high starting sugar, flavours added after fermentation and poor pH and temperature monitoring as reasons alcohol varies. Methods, limits and fundingOutcomes: Ethanol, label energy and sugars, brewer practices Read: |
| Pereira 2026 Kombucha as a Bioactive Functional Beverage: Current Evidence, Production Challenges, and Future Perspectives. Int J Mol Sci · PMID 41898599 · DOI |
Narrative review |
Review of kombucha composition, production and safety | Kombucha Drink |
Says kombucha's composition varies a lot with fermentation conditions, and that current knowledge is fragmented across fields. Describes phenolic compounds and organic acids as the main bioactive components. Methods, limits and fundingOutcomes: Composition, bioactivity, production, safety Read: |
| Phan 1998 Lead poisoning from drinking Kombucha tea brewed in a ceramic pot. Med J Aust · PMID 9887919 · DOI |
Case report |
2 A married couple |
Home-brewed kombucha made in a ceramic pot Drink About 6 months |
Two cases of symptomatic lead poisoning needing chelation therapy after about six months of drinking kombucha brewed in a ceramic pot. The authors suggest the acidic tea pulled lead out of the glaze. Methods, limits and fundingOutcomes: Symptomatic lead poisoning Read: |
| Pierce 2023 Millennial drinks: acidity, fluoride content, and enamel softening. Gen Dent · PMID 37358581 |
Laboratory study |
13 beverages; extracted human molars | One kombucha among 13 drinks Drink 30-minute immersion · vs Other drinks |
All drinks were acidic (pH 2.652 to 4.242). The kombucha tested (pH 2.820) softened enamel second most, after an energy drink. The authors say consumers should know the erosive potential of drinks. Lab study on extracted teeth. Methods, limits and fundingOutcomes: pH, fluoride, enamel hardness Read: |
| Racki 2026 Erosive potential of Kombuchas: an in vitro study in an oral cavity simulator. Odontology · PMID 40996613 · DOI |
Laboratory study |
Cow-tooth enamel and dentin specimens (108) | Two Brazilian commercial kombucha brands Drink 5 days of simulated cycles · vs Water and Coca-Cola |
One brand caused less surface loss than Coca-Cola; the other was similar to Coca-Cola; both caused more than water. The authors conclude regular consumption might raise the risk of erosive tooth wear. Lab study, not in people. Methods, limits and fundingOutcomes: Tooth surface loss Read: |
| Sannapaneni 2023 Kombucha-Induced Massive Hepatic Necrosis: A Case Report and a Review of Literature. Gastro Hep Adv · PMID 39132615 · DOI |
Case report with review |
1 One healthy woman with no past medical history |
Kombucha Drink Not in abstract Not in abstract |
Severe acute liver injury associated with drinking kombucha in a woman with no past medical history. The authors say much is unknown about the amount that can be safely ingested. Cause and effect cannot be proven from one case. Methods, limits and fundingOutcomes: Severe acute liver injury Read: |
| Wang 2022 Kombucha: Production and Microbiological Research. Foods · PMID 36360067 · DOI |
Narrative review |
Review of the microbes in kombucha | Kombucha Drink |
Describes kombucha as a sparkling sugared tea fermented for several days with a cellulose pellicle (tea fungus) of acetic acid bacteria and yeast. Yeast turn sucrose into fructose and glucose, then ethanol; acetic acid bacteria turn ethanol into acetic acid, which lowers pH and gives the sour taste. Notes that consumption has been reported as early as 220 B.C. Methods, limits and fundingOutcomes: How kombucha is made; its microbes Read: |
| de Miranda 2022 Kombucha: A review of substrates, regulations, composition, and biological properties. J Food Sci · PMID 35029317 · DOI |
Narrative review |
Review of kombucha production, composition and regulation | Kombucha Drink |
Antioxidant, antimicrobial, antidiabetic and anticancer effects are attributed to kombucha, but the authors say clinical studies in people are needed. They say toxic effects are unclear and that consumption is contraindicated in infants, pregnant women, children under 4, people with kidney failure and people with HIV; the abstract does not give the sources for that list. Sugar type and amount, time and temperature change acids, vitamins, phenolics and alcohol content. Methods, limits and fundingOutcomes: Composition, claimed benefits, regulation, safety Read: |
| s-cdc-mmwr1995 Unexplained severe illness possibly associated with consumption of Kombucha tea - Iowa, 1995 (CDC MMWR) · Source |
Public health investigation report n/a |
Methods, limits and fundingRead: full-text | ||
| s-fda-caffeine Spilling the Beans: How Much Caffeine Is Too Much? (US FDA) · Source |
Regulator consumer update n/a |
Methods, limits and fundingRead: full-text | ||
| s-gbif-camellia-sinensis GBIF Backbone Taxonomy: Camellia sinensis (L.) Kuntze (usageKey 3189635) · Source |
Taxonomy database record n/a |
Methods, limits and fundingRead: full-text | ||
| s-poison Kombucha tea: Health tonic or dangerous? (Poison Control / National Capital Poison Center) · Source |
Public health advice page n/a |
Methods, limits and fundingRead: full-text | ||
| s-ttb Kombucha (US Alcohol and Tobacco Tax and Trade Bureau) · Source |
Regulator page n/a |
Methods, limits and fundingRead: full-text |
What we do not know yet
- No trial longer than 12 weeks, and none with heart, diabetes or infection outcomes.
- Most trials are small and several are funded by or linked to kombucha makers.
- No USDA nutrition record was read; vitamins, minerals and typical sugar and caffeine in shop bottles are not known from the sources read.
- No official body statement specific to kombucha in pregnancy or breastfeeding was found.
- No study of kombucha with specific medicines was found.
- The cause of the rare serious illnesses in case reports was not proven. LiverTox, LactMed and EFSA were not checked.
- Allergy, histamine and FODMAP were not researched.
How new research is added
New studies are found by a saved PubMed search and placed in a review queue before the page changes.
Lab markers
What changed in blood or saliva tests during trials. A changed number is not the same as feeling or being healthier, and we give no "normal ranges".
Metabolic 3
Fasting blood glucose
Lowered in trials
Blood sugar after not eating for several hours.
Very low certaintyResults and what it means
Why it was measured
The usual marker of blood sugar control in diabetes studies.
Statistical vs. clinical meaning
A drop within the kombucha period; the two drinks were not compared head to head.
Safety implication
The kombucha tested had 1.5% alcohol.
| Study | Result | People | Product |
|---|---|---|---|
| 16 | 164 to 116 mg/dL with kombucha at 4 weeks (p = 0.035); 162 to 141 with placebo (p = 0.078) | 12 adults with type 2 diabetes | Kombucha 240 mL a day for 4 weeks versus placebo drink |
Triglycerides
Lowered in trials
A type of fat carried in the blood.
Very low certaintyResults and what it means
Why it was measured
High levels are linked to heart disease risk.
Statistical vs. clinical meaning
Mixed: significant against the unfermented-tea group in one funded trial, not significant between groups in the other.
Safety implication
None specific.
| Study | Result | People | Product |
|---|---|---|---|
| 2 | Group difference p = 0.031; kombucha group 69.59 to 62.80 mg/dL (p = 0.053) | 58 healthy adults | Fibre-enriched kombucha 250 mL a day for 6 weeks versus unfermented tea |
| 4 | Lower than the person's own start in the kombucha group (p = 0.012); no significant difference between groups (p > 0.05) | 59 adults with excess weight | Green tea kombucha 200 mL a day for 10 weeks with a calorie-cut diet |
LDL cholesterol
No clear change between groups in trials
The cholesterol carried in the blood that is linked to heart disease.
Very low certaintyResults and what it means
Why it was measured
The usual blood marker in diet trials for heart risk.
Statistical vs. clinical meaning
The calorie-cut diet may explain the change within the group.
Safety implication
None specific.
| Study | Result | People | Product |
|---|---|---|---|
| 4 | Lower than the person's own start in the kombucha group (p = 0.035); no significant difference between groups | 59 adults with excess weight | Green tea kombucha with a calorie-cut diet, 10 weeks |
Other 4
Glycaemic and insulin index after a meal
Lowered in trials
How much blood glucose and insulin rise after a standard meal, compared with pure glucose.
Very low certaintyResults and what it means
Why it was measured
Used to see if a drink changes how the body handles a meal.
Statistical vs. clinical meaning
A change after a single meal in 11 people.
Safety implication
None specific.
| Study | Result | People | Product |
|---|---|---|---|
| 3 | Glycaemic index 68 versus 86 and insulin index 70 versus 85 with soda water (both p = 0.041) | 11 healthy adults | Live kombucha with a high-GI meal, single meals |
Fasting insulin and HOMA-IR
Raised (within the kombucha group) in trials
Insulin in the blood after fasting, and a score (HOMA-IR) that estimates insulin resistance.
Very low certaintyResults and what it means
Why it was measured
Used to judge how well the body handles sugar.
Statistical vs. clinical meaning
A rise within one group in a small trial; the cross-group test was not significant.
Safety implication
Raised insulin resistance would not be a benefit; it needs checking in larger trials.
| Study | Result | People | Product |
|---|---|---|---|
| 7 | Fasting insulin and HOMA-IR increased within the kombucha group; no significant change across the whole cohort | 24 healthy adults | Kombucha for 4 weeks versus control |
Gut bacteria (stool sequencing)
Some groups changed in trials
The types and amounts of bacteria found in stool.
Low certaintyResults and what it means
Why it was measured
Used to see if a food changes the gut community.
Statistical vs. clinical meaning
Microbe counts shifted in three of four trials; no trial showed a health benefit from the change.
Safety implication
None specific.
| Study | Result | People | Product |
|---|---|---|---|
| 7 | Weizmannia and several short-chain-fatty-acid-producing groups more abundant at the end | 24 healthy adults | Kombucha 4 weeks |
| 6 | Subdoligranulum up in the obesity group (P = 0.031); Ruminococcus and Dorea down | 46 adults, no control group | Black tea kombucha 8 weeks |
| 2 | Bifidobacterium up, Ruminococcus torques down | 58 healthy adults | Fibre-enriched kombucha 6 weeks vs unfermented tea |
| 8 | No significant difference between groups | 59 adults with excess weight | Green tea kombucha 10 weeks |
Neutrophils and lymphocytes
Exploratory shifts in trials
Two types of white blood cell.
Not enough evidenceResults and what it means
Why it was measured
Used as a rough marker of immune response.
Statistical vs. clinical meaning
May be chance after adjusting for multiple tests.
Safety implication
None established.
| Study | Result | People | Product |
|---|---|---|---|
| 5 | Neutrophils up (p = 0.026) and lymphocytes down (p = 0.023) in the kombucha group versus the other groups; authors call it exploratory | 90 healthy adults | Green tea kombucha 12 weeks |
Safety
What studies and official sources say about side effects, medicines and who should check first. Each point shows what kind of evidence it comes from.
Main points to know 5
- Alcohol: it varies, and it can be more than the label suggests. Fermentation makes alcohol. In a survey of 684 kombucha samples in British Columbia, alcohol ranged from none detected to 3.62% (average 0.77%) and 31.5% of samples were above the province's 1% limit for non-alcoholic drinks. In New Zealand, 2 of 9 samples were over the 1.15% limit. US TTB treats kombucha that reaches 0.5% or more at any point, even after bottling, as an alcohol beverage. Poison Control says some commercial products were recalled for more alcohol than advertised. This matters for children, pregnancy, people who avoid alcohol and people on medicines that warn against alcohol. Laboratory survey and regulator 12 18 30 29 1
- Pregnancy, young children and weak immune systems: avoid, say the sources read. Poison Control advises that young children, pregnant women and people with weakened immune systems should not drink kombucha, store-bought or home-brewed. A 2022 review says consumption is contraindicated in infants, pregnant women, children under 4, people with kidney failure and people with HIV, but its abstract does not give the evidence behind that list. No official pregnancy statement on kombucha itself was found. Public health advice and review 29 25
- Rare serious illness reported, cause not proven. Case reports link kombucha with lactic acidosis, severe liver injury and lead poisoning. In 1995 in Iowa, one woman died and one survived cardiac arrest after daily kombucha, but the CDC report could not show that the tea caused it. These are rare reports, not a measured rate, and most describe home-brewed or unusual products. Poison Control also lists hepatitis, cardiac arrest, heart muscle inflammation and skin anthrax with home-brewed kombucha, none attributed to bacterial contamination. Case reports 26 11 23 10 29
- Lead from ceramic pots. Two case reports and an outbreak investigation describe lead poisoning from kombucha made or stored in ceramic containers. The acidic tea is thought to pull lead out of the glaze. Lead in kombucha in the outbreak reached 47 mg/kg in the packaged drink. Case reports and outbreak 20 17 29
- Acid and teeth. Lab studies found kombucha is acidic (pH 2.82 to 3.66 in one study) and softened or etched tooth enamel, in some cases as much as or more than cola. These studies were on extracted or animal teeth, not people. Laboratory 14 21 22
Side effects 4
| Effect | How often | Severity and recovery | Evidence |
|---|---|---|---|
| Alcohol exposure from a drink labelled as a soft drink Surveys are from British Columbia and New Zealand; other places and brands will differ. | Survey of 684 samples (British Columbia): mean 0.77% alcohol, up to 3.62%; 31.5% over 1%. | depends on the person; matters most in pregnancy, children, alcohol avoidance Not applicable. | Product survey 12 18 30 1 |
| Lactic acidosis (too much lactic acid in the blood) Cause was not proven in the CDC investigation. | Case reports only; no rate found. | can be life-threatening The 2017 UK case recovered fully after stopping the tea; one 1995 Iowa patient died and one recovered. | Case reports 11 26 |
| Tooth enamel erosion Lab studies on extracted or bovine teeth. | Not measured in people. | mild to moderate over time (lab suggestion) Enamel loss is not reversible. | Laboratory 14 21 22 |
| Caffeine effects The FDA page is about caffeine in general and does not mention kombucha. | No typical caffeine amount for shop kombucha was found. A lab study of four brewed green tea batches had caffeine in all, the lowest at 114 mg/L. | depends on sensitivity Not described for kombucha. | Laboratory and regulator 9 27 |
Liver
Two case reports describe severe liver injury after kombucha, one called massive liver cell death in a healthy woman, and Poison Control lists several cases of hepatitis with home-brewed kombucha. The details of the 2016 case were not available in the abstract. None proves the tea was the cause. LiverTox was not checked for kombucha. 23 10 29
How often. No frequency was found.
Monitoring. No agency monitoring advice was found.
- .
- .
This is a safety connection. It is not evidence that Kombucha supports liver health.
Medicines and supplements 3
| With | Why it matters | Importance | Evidence | What to do |
|---|---|---|---|---|
| Alcohol-restricting situations: medicines that warn against alcohol, and recovery from alcohol misuse prescription | Kombucha contains alcohol that varies from almost none to over 3% in tested products. | No source read tested kombucha with specific medicines. This is a caution based on measured alcohol content, not a documented interaction. | Theoretical Not enough evidence 12 18 1 | If your medicine label says to avoid alcohol, or you avoid alcohol for health or personal reasons, ask a pharmacist or doctor about kombucha. |
| Medicines for diabetes prescription | Two very small trials saw lower blood sugar readings after kombucha. | No source read tested kombucha with diabetes medicines. A large change in drinks could in theory add to a medicine's effect. | Theoretical Not enough evidence 16 3 | Tell your care team if you start drinking kombucha regularly. |
| Caffeine-sensitive conditions and caffeine-containing products food-and-drink | Kombucha is made from tea and contains caffeine, which adds to coffee, tea and energy drinks. | No typical amount was found. The FDA caffeine page is general advice and does not mention kombucha. | Regulator general advice Not enough evidence 9 27 | If you have been told to limit caffeine, include kombucha when you count it. |
Who should check first 5
| Situation | Advice | Evidence |
|---|---|---|
| Pregnancy or trying to become pregnant | Poison Control says pregnant women should not drink kombucha. The alcohol amount varies and the FDA asks pregnant people to talk to a provider about caffeine. Ask your midwife or doctor. | Public health advice 29 25 27 |
| Breastfeeding | No kombucha-specific statement was found. The FDA asks people who are breastfeeding to talk to a provider about limiting caffeine, and alcohol content varies. Ask your midwife or doctor. | Regulator general advice 27 12 |
| Infants and young children | Poison Control says young children should not drink kombucha; a review lists infants and children under 4. Alcohol content varies and the drink is acidic and may contain caffeine. | Public health advice 29 25 12 |
| Weakened immune system, kidney failure or HIV | Poison Control says people with weakened immune systems should not drink it. A review lists kidney failure and HIV as contraindications without giving the sources in the abstract. Ask your clinician. | Public health advice and review 29 25 |
| Avoiding alcohol or caffeine | Check the label and ask the maker. Alcohol and caffeine are present in kombucha and vary. | Product survey 12 18 9 |
Overdose, product quality and regulators
Summary. No toxic dose is known. A 2022 review says the toxic effects of kombucha are still unclear. The documented problems are case reports (lactic acidosis, liver injury), lead from ceramic containers, variable alcohol and acidity.
Animal. Not reviewed.
High dose or long term signals. The 1995 CDC report notes one patient had increased her daily intake and lengthened the fermentation time shortly before illness, but could not show this caused it.
Overdose response. Not found.
Genotoxicity. Not researched.
Lead from ceramic or glazed containers is the best-documented contamination problem. Poison Control says contamination is possible if home brewing is not done carefully. Pesticide, mould and heavy-metal testing of shop kombucha was not found.
Lead from ceramic containers. Two cases of symptomatic lead poisoning after kombucha was brewed in a ceramic pot (1998), and a family outbreak in Spain where kombucha made in ceramic containers contained up to 47 mg/kg of lead. 20 17
Home brewing. Poison Control says contamination is possible if home brewing is not carried out carefully; reported cases were not attributed to bacterial contamination. 29
Alcohol variation between bottles. Alcohol rose above labels or limits in a share of tested products, and in-bottle fermentation can keep raising it. 12 18 30
| Body | Action | Date |
|---|---|---|
| US TTB (Alcohol and Tobacco Tax and Trade Bureau) (United States) | Kombucha at 0.5% alcohol by volume or more at any point in production, at bottling or after bottling is an alcohol beverage under TTB rules; kombucha that never reaches 0.5% falls under FDA rules. source | 2019-08-13 |
| Poison Control (National Capital Poison Center) (United States) | Advises young children, pregnant women and people with weakened immune systems not to drink kombucha; says there are no scientific studies supporting the health claims; notes lead poisoning from ceramic brewing containers and recalls for higher alcohol. source | |
| US CDC (MMWR) (United States) | 1995 report on two Iowa women with severe lactic acidosis after daily kombucha; causal link not established; advised doctors to consider kombucha in unexplained lactic acidosis and to report to FDA MedWatch. source | 1995 |
| US FDA (United States) | Caffeine: 400 mg a day is generally not linked to negative effects for most adults; people who are pregnant or breastfeeding should ask a provider about limiting caffeine. Page does not mention kombucha. source | 2024-08-28 |
When to get medical help
- Trouble breathing, fast breathing, collapse or feeling very unwell after drinking kombucha (these were features of the lactic acidosis case reports): get urgent medical care.
- Symptoms of lead poisoning or liver injury after drinking home-brewed or ceramic-stored kombucha: see a doctor and say what you drank.
- If you are unsure, call your local poison centre or emergency number.
Stop using the product and contact a clinician or emergency service. In the US, Poison Control is 1-800-222-1222.
General information only, not medical advice. Ask a clinician or pharmacist before use, especially with medicines, in pregnancy or with a health condition. See the Natural Remedy Safety guide.
Frequently asked questions
What is kombucha?
Kombucha is a sparkling, sugared tea fermented with bacteria and yeast. It tastes sour because of acetic acid.
Does kombucha help digestion or gut health?
Does kombucha lower blood sugar?
Does kombucha lower cholesterol?
Does kombucha contain alcohol?
Is kombucha safe in pregnancy?
Can children drink kombucha?
Does kombucha contain caffeine?
Can kombucha harm your teeth?
Is home-brewed kombucha risky?
Is kombucha a probiotic?
Not automatically. Experts separate fermented foods from probiotics. Whether a bottle has live microbes depends on the product and label.
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Editorial transparency
- Written by
- AlternativeMed editorial team. Research compiled with AI assistance, then checked against the sources listed.
- Medical review
- None. This page has not been reviewed by a physician or pharmacist.
- First published
- 2026-10-26
- Last substantive update
- 2026-10-26
- How we research
- We started from our earlier kombucha page, re-read every PubMed abstract listed, and read the pages of TTB, CDC, FDA and Poison Control. Only abstracts were read for studies. Items we could not verify are flagged in the research gaps.
- How we rate evidence
- See "How we rate evidence" in the Evidence tab.
- Independence
- No product is promoted on this page. No affiliate links are shown. Several trials cited were funded by or linked to kombucha makers; this is stated where each is used.
Sources 30
Each source was opened and checked. Where we read only the abstract, it says so. The small numbers in the text point here.
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- . Unexplained severe illness possibly associated with consumption of Kombucha tea - Iowa, 1995 (CDC MMWR). . . (full-text)
- . Spilling the Beans: How Much Caffeine Is Too Much? (US FDA). . . (full-text)
- . GBIF Backbone Taxonomy: Camellia sinensis (L.) Kuntze (usageKey 3189635). . . (full-text)
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