Glycemic Control

Kombucha tea as an anti-hyperglycemic agent in humans with diabetes - a randomized controlled pilot investigation (2023)

A prospective randomized double-blinded crossover study, with 12 subjects

“Kombucha lowered average fasting blood glucose levels at 4 weeks compared to baseline (164 vs. 116 mg/dL, p = 0.035), whereas the placebo did not (162 vs. 141 mg/dL, p = 0.078).”

• possibly positive for blood sugar levels but small sample size

Glycemic Control

Modulating the human gut microbiome and health markers through kombucha consumption: a controlled clinical study (2024)

“paired analysis between baseline and end of intervention time points within kombucha or control groups revealed increases in fasting insulin and in HOMA-IR in the kombucha group”

• Generally not a good thing for blood sugar management
• unclear how much sugar in the kombucha: “16 oz of a commercial kombucha beverage”
• small study, only 24 participants

Glycemic Control

Glycemic index and insulin index after a standard carbohydrate meal consumed with live kombucha: A randomised, placebo-controlled, crossover trial

2023 Study, 11 participants, on post-prandial glucose response of kombucha compared to 2 other drinks

• 330 ml of Schweppes soda water (placebo)
• diet lemonade soft drink (Schweppes Zero Sugar)
• organic kombucha (The Good Brew Company Pty Ltd., VIC, Australia)

The Kombucha added 3g of carbohydrate (1.7g sugar) to the test meal

Soda water and diet lemonade did not contain any sugar.

Glycemic Control

Gut Health

2024 RCT: Kombucha and the Gut Microbiome
8-week trial in 30 healthy adults

• No change in overall diversity, but specific species shifted

• Probiotic increases:
  

  • Weizmannia coagulans — probiotic added to kombucha

  • SCFA producers (e.g. Prevotella, Bifidobacterium) → may support gut lining and reduce inflammation

  • Ellagibacter — helps break down dietary polyphenols

• Probiotic decreases:
  

  • ↓ Fusobacterium, Parabacteroides — possibly favorable

  • ↓ Lactobacillus — often beneficial; unclear impact here

• No effect on blood biomarkers or inflammation

• Suggests short-term microbial reshaping from probiotics + fiber;
  clinical impact unclear without longer trials

Gut Health

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

10 week study on 59 participants from 2024

GI symptom improvements (vs. control)

• Reduced hard stools (p = 0.001)
• Improved sensation of not completely emptying the intestine (p = 0.027; Δ p = 0.002)
• Less “having a stomach full of air” (p = 0.046)
• Reduced reflux (p = 0.043)
• Lower total GSRS symptom score (p = 0.035) (Gastrointestinal Symptom Rating Scale)

Gut Barrier-related outcomes

• Intestinal permeability and fecal pH worsened in controls only
• Suggests kombucha may help maintain gut barrier and pH balance

Gut Health

Constipation-Predominant IBS (irritable bowel syndrome)

• 40 women with IBS-C
• Increased stool frequency (0.60 → 0.85/day, p = 0.004)
• Stool consistency improved
• Reduced incomplete evacuation; no adverse effects
• Inulin may explain at least part of the benefit

Inflammatory Bowel Disease (Crohn’s, UC)

• No human trials; only anecdotal symptom reports
• Mouse study: kombucha polysaccharide reduced colitis severity, improved gut barrier integrity
• Live cultures may pose risk, caution advised in IBD

Gut Health

• The study on green tea kombucha states:
  “Kombucha has been associated with decreasing gastrointestinal symptoms in individuals with inflammatory bowel disease [17].”

• But reference [17] is a pilot RCT in women with IBS-C — it does not mention IBD or its subtypes (Crohn’s, ulcerative colitis)

• A Google Scholar search for “kombucha inflammatory bowel disease” ranks the IBS study among the top results

• IBS: Discomfort without long-term damage (pain, bloating, irregularity)
• IBD: Chronic inflammation with risk of bleeding, hospitalization, complications

Anti-inflammatory Effects

Green Tea Kombucha Impacts Inflammation and Salivary Microbiota in Individuals with Excess Body Weight: A Randomized Controlled Trial

Anti-oxidant Effects

Human Evidence:

• No human randomized controlled trials have directly measured anti-oxidant biomarkers

• Reviews emphasize a lack of direct anti-oxidant outcome trials in humans

  • Batista et al., 2023

Anti-oxidant Effects

Animal & in vitro evidence:

• Kombucha reduces oxidative stress in hepatocytes and rodent tissues
  • lower lipid peroxidation (MDA), ↑ Anti-oxidant enzymes (SOD, catalase, GSH) in liver and kidney cells
    
  • More potent than black tea in models of toxicant exposure
• Kombucha’s fermentation enhances Anti-oxidant capacity
  • Increases total phenolic content and free-radical scavenging (DPPH, hydroxyl, superoxide assays)
    
  • Stronger Anti-oxidant activity than unfermented tea

Liver Function & Kombucha

• No human trials yet on kombucha in liver disease, NAFLD, or elevated liver enzymes
  
• Animal models show strong hepatoprotective effects in metabolic and toxic injury contexts

• Toxin-induced injury (rats): kombucha-fermented black tea lowered ALT, AST, ALP, MDA; protected against necrosis, better than black tea.
• Fatty liver (NAFLD) models: reduced hepatic steatosis and inflammation in high-fat/fructose-fed rats
• Diabetic models: improved liver and kidney function in diabetic rats

Adverse Effects & Warnings

• Mild GI symptoms common in trials (e.g. bloating, diarrhea) (Ecklu-Mensah et al., 2024)

• Serious liver injury reported:
  

  • Case of acute cholestatic hepatitis after ~1 month of kombucha use
    in a woman with diabetes and hypothyroidism; resolved with treatment

  • (Gedela et al., 2023, Heliyon)

• Iowa CDC case (1995):
  

  • Two women hospitalized after drinking homemade kombucha for 2 months;
    one died from severe metabolic acidosis

  • “Possibly Associated with Consumption of Kombucha Tea”

  (CDC MMWR, 1995)

Caution: Most serious harms involved improperly prepared homemade or excessive daily use.
When brewed safely and consumed in moderation, kombucha appears well-tolerated by most.

Kombucha Health Effects