New research reveals how green tea kombucha alleviates gut issues, enhances metabolic markers, and supports healthier weight loss—offering a delicious edge in dietary interventions.

Study: 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. Image Credit: Liv friis-larsen / Shutterstock

In a recent randomized controlled trial published in the journal Foods, researchers investigated the effects of green tea kombucha (GTK) consumption on gut health, microbiota, and metabolism in individuals with excess body weight on an energy-restricted diet. They found that GTK consumption did not significantly affect gut microbiota or intestinal permeability but improved gastrointestinal symptoms and altered the serum metabolome by influencing specific metabolites linked to anti-inflammatory and antioxidant properties. These findings suggest potential benefits for metabolic health in individuals with excess body weight.

Background

Fermented foods, like kombucha, have gained popularity for their potential health benefits, particularly in improving intestinal health, modulating microbiota, and combating metabolic imbalance.

Kombucha, made by fermenting sugar-containing green or black tea with a symbiotic culture of bacteria and yeasts, contains bioactive compounds such as phenolic acids, organic acids, and vitamins. Despite its growing consumption, the true effects of kombucha on human health, particularly in individuals with excess body weight, remain unclear. Overweight individuals often experience altered gut microbiota, lower diversity, and a weakened intestinal barrier, contributing to inflammation and metabolic disorders.

Studies in animal models suggest kombucha may reduce gut dysbiosis and improve intestinal health. However, no human studies prior to this have evaluated GTK’s role when combined with an energy-restricted diet in terms of both intestinal parameters and serum metabolomics. Therefore, researchers in the present study examined, for the first time, the effect of GTK on gastrointestinal symptoms, intestinal permeability, microbiota composition, and serum metabolites in individuals with excess body weight undergoing weight loss treatment.

About the study

Participants with excess body weight (body mass index ≥ 27 kg/m², body fat > 30% for women, > 25% for men) were randomly assigned to two groups: a control group (CG, n = 37) following an energy-restricted healthy diet and a kombucha group (KG, n = 38) receiving the same diet with an additional 200 mL/day of GTK over a 10-week period. Exclusion criteria were the presence of metabolic or chronic diseases, habitual use of supplements, or regular consumption of fermented foods or teas. The GTK was produced in-house, with each serving providing probiotics at 1 billion colony-forming units.

Participants’ usual physical activity patterns and dietary habits were maintained and monitored throughout. Questionnaires, anthropometry, biological sample collection, and metabolic tests were used to evaluate outcomes, quality of life, and gastrointestinal symptoms of patients.

Microbiota analysis was conducted to assess diversity, differential taxa trends such as increased Romboutsia and decreased Alistipes, and correlations with metabolites in the GTK group. The metabolome was studied using serum samples.

Results and discussion

Both the KG and CG groups experienced weight loss and improvements in body composition, although no significant differences were observed between them. The KG group also experienced a slight increase in daily fiber intake, but it was not found to be statistically significant.

In terms of quality of life, CG showed improvements in total score, physical function, and bodily pain, while the KG showed improvements in total score, general health, vitality, and emotional role, but no significant differences were noted between the groups.

Intestinal parameters, including zonulin (biomarker for impaired gut barrier function), lipopolysaccharide-binding protein, SCFAs, and fecal pH, did not show significant differences between groups after the intervention, except for the CG, which showed increased levels of lactulose/mannitol ratio, fecal pH, and zonulin. Both groups showed a decrease in butyric acid production, but no significant changes were observed in other SCFAs.

In terms of gastrointestinal symptoms, both groups reported reductions, but the KG showed more substantial improvements, especially in symptoms like hard stools and incomplete bowel evacuation. The KG also showed more significant changes in stool consistency, with an increase in type 4 stool.

Further, no significant differences were found between the groups at the genus level, though the KG had a trend of decreased Alistipes and increased Romboutsia counts. Alpha diversity increased in both groups, with a statistically significant higher Chao 1 index in the KG at the genus level compared to baseline.

Lastly, serum metabolomics identified 25 putative metabolites in the KG, predominantly related to amino acid and fatty acid metabolism, including diethyl malonate and taurine, with correlations observed between changes in microbiota and metabolites.

The study’s rigorous design strengthens it, but its relatively small sample size and insufficient biological samples limit it. The use of in-house GTK, while standardized, may also differ from commercial versions, which could influence generalizability.

Conclusion

In conclusion, the study showed that GTK improved gastrointestinal symptoms, particularly in promoting complete bowel emptying and alleviating hard stools, in individuals with excess body weight undergoing weight loss treatment. While it did not significantly modulate gut microbiota, trends in increased diversity and specific taxa shifts were observed, warranting further investigation in future trials. The CG showed worsening intestinal permeability and fecal pH, suggesting that kombucha might help prevent these negative effects.

Additionally, kombucha consumption affected the serum metabolome, with metabolites linked to metabolic, anti-obesity, anti-inflammatory, and antioxidant pathways, potentially enhancing overall health in individuals with excess body weight.