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NCT Number: NCT06759324

Kombucha in Overweight and Obese: Live Vs. Pasteurized Effects on Microbiota, Metabolism, and Liver Function

Kombucha, a fermented beverage made from Camellia sinensis tea (black, oolong, or green) with sugar and a symbiotic culture of bacteria and yeast (SCOBY), has gained global attention for its potential health benefits. Factors like the type and amount of sugar substrate, fermentation time, and temperature significantly influence its organic compounds, total phenolics, vitamin content, and alcohol levels.

In a previous study, kombucha's impact on glucose tolerance, insulin sensitivity, body composition, and liver function was tested in male prediabetic mice with diet-induced obesity. Daily supplementation (200 µL per mouse) improved glucose tolerance after nine days (equivalent to one year in humans) and reduced liver steatosis, despite no changes in body composition.

Although kombucha has been associated with antioxidant, antimicrobial, probiotic, antidiabetic, and anticancer activities, strong scientific evidence in humans remains limited. Further clinical studies are needed to substantiate kombucha's health benefits in humans.

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Key information

Conditions

Obesity and Overweight Body Weight Nutrition Disorders Nutritional and Metabolic Diseases Obesity Overnutrition Overweight Pathological Conditions, Signs and Symptoms Signs and Symptoms

Age range

18 year–60 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

Centro de Apoio Tecnológico Agro Alimentar (CATAA), Castelo Branco, Castelo Branco District, Portugal

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About this study

The objectives of this clinical study aim to explore the effects of kombucha on the health of individuals with overweight and class 1 obesity, while also determining whether the kombucha microbiota plays a role in the observed effects. Specifically, by investigating metabolic parameters such as glucose and insulin levels and lipid profile, as well as the composition and diversity of the gut microbiota and liver function, the study will contribute to a deeper understanding of the potential benefits and mechanisms of action of kombucha consumption in humans. The study aims to recruit at least 30 individuals with overweight and class 1 obesity, aged between 18 and 60 years, randomly distributed into 3 arms (each arm should have about 10 participants). The first arm receives a daily amount of 33 cl of kombucha (live drink) for 4 weeks, the second arm receives a daily amount of 33 cl of kombucha (pasteurized drink) for 4 weeks. The control group receives 33 cl of sparkling water for 4 weeks.

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

Individuals with a Body Mass Index (BMI) between 25 kg/m² and 34.9 kg/m², of both biological sexes, aged between 18 and 60 years, available to comply with the study protocol (described in this document) and sign informed consent.

Exclusion criteria

Volunteers will be excluded from the study if they present one or more of the following conditions:

  • Subjects with sensitivity to kombucha;
  • Consumption of kombucha, kefir, kimchi, cheese, raw vinegar, sauerkraut, kvass, and other fermented products during the study and in the 3 weeks before the study.
  • Use of antibiotics in the 6 months prior to the start of the study;
  • Use of pro/prebiotics or fibers as dietary supplements or any food/molecule that modifies intestinal transit time 6 weeks before recruitment; use of laxatives 6 weeks before recruitment;
  • Specific dietary regimen (e.g., vegan); specific dietary treatment (e.g., high protein);
  • Excessive consumption of substances and alcohol; smokers;
  • Diagnosis of gastrointestinal disorders, hormonal or thyroid diseases, autoimmune diseases, and/or chronic use of corticosteroids; psychiatric disease; Type 1 or 2 diabetes;
  • Use of proton pump inhibitors; antidiabetic drugs or insulin and statins;
  • Subjects with insulin sensitivity;
  • Pregnant or lactating women;
  • Subjects with tooth sensitivity
  • Participation in another clinical trial in the last 3 months.

Treatment and study plan

Live kombucha (non filtered/ non pasteurized)

Dietary Supplement

Participants receive a daily amount of 33 cl of live kombucha (non-pasteurized/ non-filtered) for 4 weeks (28 days).

Pasteurized kombucha (non filtered)

Dietary Supplement

Participants receive a daily amount of 33 cl of kombucha (pasteurized drink) for 4 weeks (28 days).

Control (sparkling water)

Other

Participants receive a daily amount of 33 cl of sparkling water for 4 weeks.

Primary outcomes

  1. Change in Gut microbiota composition and diversity (fecal samples)

    Time frame: 4 weeks

    Analyze the changes in the relative abundance of the microbial species present, including taxonomic identification and diversity analysis, from baseline to the end of intervention, by next-generation sequencing (NGS).

  2. Change in fasting glucose levels

    Time frame: 4 weeks

    Fasting glucose (mg/dl), from baseline to the end of intervention. Reduction is a better outcome.

  3. Change in fasting insulin levels

    Time frame: 4 weeks

    Fasting insulin (μUI/mL), from baseline to the end of intervention. Reduction is a better outcome.

  4. Changes in Homeostasis Model Assessment of Insulin Resistance (HOMA-IR) values

    Time frame: 4 weeks

    HOMA-IR values, from baseline to the end of intervention. Calculated from fasting glucose (mmol/L) X fasting insulin (mU/L) / 22.5). Less than 1.0 means insulin-sensitive, which is optimal. Above 1.9 indicates early insulin resistance. Above 2.9 indicates significant insulin resistance. Reduction is a better outcome.

  5. Changes in Lipid profile

    Time frame: 4 weeks

    Lipid profile (total cholesterol, LDL cholesterol, HDL cholesterol and triglycerides), in mg/dL, from baseline to the end of intervention.

Secondary outcomes

  1. Stool consistency rating by Bristol Stool Scale

    Time frame: 4 weeks

    The Bristol Stool Chart is a medical tool used to classify human feces into seven distinct categories. This scale is widely regarded as the gold standard for evaluating stool consistency and intestinal transit time in adults. It ranges from type 1 (separate hard lumps), which indicates the slowest transit time and constipation, to type 7 (watery with no solid pieces), representing the fastest transit time. Daily monitoring questionnaire (to evaluate 1 to 7), from baseline to the end of intervention.

  2. Variation in SIBO diagnosis (positive/negative) measured by methane and hydrogen levels in breath test

    Time frame: 4 weeks

    Hyrogen and methane lactulose breath test, in ppm, from baseline to end of intervention. Interpretation criteria: SIBO test is positive if there is an early increase (in the first 90 minutes) equal to or greater than 20 ppm of H2 and/or equal to or greater than 10 ppm of CH4, when compared with the lowest value obtained.

  3. Change in liver enzyme levels

    Time frame: 4 weeks

    Analyze liver enzymes (units: in UI/L) such as alkaline phosphatase, alanine transaminase, aspartate transaminase, gamma-glutamyl transferase, from baseline to end of intervention, to determine potential hepatic effects of Kombucha consumption.

  4. Change in levels of oxidative stress biomarker (ratio 8-iso-PGF2α to prostaglandin F2α (PGF2α))

    Time frame: 4 weeks

    Measure of oxidative stress biomarker (pg/mL ), from baseline to the end of intervention. Normal human plasma reference values: 40-100 pg/mL.

  5. Change in gastrointestinal symptoms using a Likert scale

    Time frame: 4 weeks

    Evaluate gastrointestinal symptoms (e.g., bloating, gas) using a 10-point Likert scale, from baseline to the end of intervention. The daily questionnaire goes from zero (0) which means "no pain" to ten (10) which means "worst pain imaginable".

  6. Change in high-sensitive C-reactive protein levels

    Time frame: 4 weeks

    Levels of h-sensitivity C-reactive protein (hsCRP), a marker of inflammation, in mg/dL, from baseline to the end of intervention. hsCRP levels of less than 0.100, 0.100 to 0.300, and greater than 0.301 mg/dL are associated with lower, moderate, and higher cardiovascular risks, respectively.

  7. Change in Total oxidant capacity

    Time frame: 4 weeks

    Oxidative stress biomarker, pg/mL, measured from baseline to the end of intervention. Normal values range from 40-100.

  8. Changes in serum albumin and bilirubin levels

    Time frame: 4 weeks

    Evaluate hepatobiliary function, albumin (g/dL), Bilirubin (mg/dL)

  9. Changes in short chain fatty acids in stool

    Time frame: 4 weeks

    SCFAs in stool, units µM

Other outcomes

  1. Body weight change

    Time frame: 4 weeks

    Anthropometric measurement, unit of measure: Kg

  2. BMI change

    Time frame: 4 weeks

    Body mass index (BMI) is a measure of body fat based on height and weight, unit of measure: Kg/m2

  3. Waist circumference change

    Time frame: 4 weeks

    Anthropometric measurement, unit of measure: cm

  4. Body fat percentage change

    Time frame: 4 weeks

    unit of measure: %

  5. Changes in kidney function biomarkers- creatinin, urea and uric acid

    Time frame: 4 weeks

    units in mg/dL

Study contacts

Contact information is provided by the study sponsor or research team.

Filomena Pereira, Nutritionist

CONTACT

[email protected]

Inês Brandão, PhD

CONTACT

[email protected]

+351926777221

Sponsors and collaborators

Lead sponsor

Associação Centro de Apoio Tecnológico Agro Alimentar

Other

Registry information

Official study title

Randomized Controlled Pilot Clinical Study Including Kombucha in the Diet of Individuals with Overweight and Class 1 Obesity: Comparative Assessment Between Live and Pasteurized Kombucha and Its Effects on Gut Microbiota, Metabolic Parameters, and Liver Function [FUSILLI Project -H2020]

Acronym: KOMBIOME

Important dates

Study start
2024
Primary completion
2025
Study completion
2025
First posted
Jan 6, 2025
Registry last updated
Jan 6, 2025

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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