Obesity and Overweight
Conditions
Keywords
kombucha, gut microbiota, obesity, liver function, fermented beverages, Randomized Controlled Trial, overweight, fermented tea, SCOBY, live vs pasteurized kombucha, Small Intestinal Bacterial Overgrowth (SIBO), Bristol Stool Form Scale, Likert Scale Analysis, Nutritional Interventions, Inflammatory Biomarkers, metabolic parameters
Brief summary
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.
Detailed description
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.
Interventions
DIETARY_SUPPLEMENTLive kombucha (non filtered/ non pasteurized)
Participants receive a daily amount of 33 cl of live kombucha (non-pasteurized/ non-filtered) for 4 weeks (28 days).
DIETARY_SUPPLEMENTPasteurized kombucha (non filtered)
Participants receive a daily amount of 33 cl of kombucha (pasteurized drink) for 4 weeks (28 days).
OTHERControl (sparkling water)
Participants receive a daily amount of 33 cl of sparkling water for 4 weeks.
Sponsors
Associação Centro de Apoio Tecnológico Agro Alimentar
Study design
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
OTHER
Masking
TRIPLE (Subject, Investigator, Outcomes Assessor)
Masking description
Partial double blinding (participants will not know if they are consuming live or pasteurized kombucha; the nutritionist will not know which arm the participant belongs to; the technician responsible for microbiota sequencing will receive coded samples without information regarding the intervention/control arm the sample belongs to).
Intervention model description
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 water for 4 weeks. Kombucha samples are prepared for the study by Erfrischerling GmbH & Co. KG (Germany).
Eligibility
Sex/Gender
ALL
Age
18 Years to 60 Years
Healthy volunteers
No
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: 1. Subjects with sensitivity to kombucha; 2. 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. 3. Use of antibiotics in the 6 months prior to the start of the study; 4. 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; 5. Specific dietary regimen (e.g., vegan); specific dietary treatment (e.g., high protein); 6. Excessive consumption of substances and alcohol; smokers; 7. Diagnosis of gastrointestinal disorders, hormonal or thyroid diseases, autoimmune diseases, and/or chronic use of corticosteroids; psychiatric disease; Type 1 or 2 diabetes; 8. Use of proton pump inhibitors; antidiabetic drugs or insulin and statins; 9. Subjects with insulin sensitivity; 10. Pregnant or lactating women; 11. Subjects with tooth sensitivity 12. Participation in another clinical trial in the last 3 months.
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Change in Gut microbiota composition and diversity (fecal samples) | 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). |
| Changes in Lipid profile | 4 weeks | Lipid profile (total cholesterol, LDL cholesterol, HDL cholesterol and triglycerides), in mg/dL, from baseline to the end of intervention. |
| Changes in Homeostasis Model Assessment of Insulin Resistance (HOMA-IR) values | 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. |
| Change in fasting insulin levels | 4 weeks | Fasting insulin (μUI/mL), from baseline to the end of intervention. Reduction is a better outcome. |
| Change in fasting glucose levels | 4 weeks | Fasting glucose (mg/dl), from baseline to the end of intervention. Reduction is a better outcome. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Change in high-sensitive C-reactive protein levels | 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. |
| Change in Total oxidant capacity | 4 weeks | Oxidative stress biomarker, pg/mL, measured from baseline to the end of intervention. Normal values range from 40-100. |
| Changes in serum albumin and bilirubin levels | 4 weeks | Evaluate hepatobiliary function, albumin (g/dL), Bilirubin (mg/dL) |
| Changes in short chain fatty acids in stool | 4 weeks | SCFAs in stool, units µM |
| Change in gastrointestinal symptoms using a Likert scale | 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. |
| Stool consistency rating by Bristol Stool Scale | 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. |
| Variation in SIBO diagnosis (positive/negative) measured by methane and hydrogen levels in breath test | 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. |
| Change in liver enzyme levels | 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. |
| Change in levels of oxidative stress biomarker (ratio 8-iso-PGF2α to prostaglandin F2α (PGF2α)) | 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. |
Other
| Measure | Time frame | Description |
|---|---|---|
| Body weight change | 4 weeks | Anthropometric measurement, unit of measure: Kg |
| Changes in kidney function biomarkers- creatinin, urea and uric acid | 4 weeks | units in mg/dL |
| Body fat percentage change | 4 weeks | unit of measure: % |
| Waist circumference change | 4 weeks | Anthropometric measurement, unit of measure: cm |
| BMI change | 4 weeks | Body mass index (BMI) is a measure of body fat based on height and weight, unit of measure: Kg/m2 |
Countries
Portugal
Contacts
Primary ContactInês Brandão, PhD
Backup ContactFilomena Pereira, Nutritionist
Outcome results
None listed