Introduction: Green tea kombucha (GTK) is a fermented tea that emerged as a promising probiotic antioxidant beverage. Nevertheless, no clinical trials have investigated its effect on human intestinal microbiota and serum metabolites. This study aimed to bridge this gap by examining the influence of GTK on microbiota diversity and composition, and serum metabolites of individuals with excess body weight.

Methodology: This is a randomized controlled clinical trial, that lasted ten weeks with two parallel groups: the control group (n=29) under a healthy diet with energy restriction (-500 kcal/day), and the kombucha group (n=30) with the same diet + GTK (200 ml/day). Fecal and serum samples were collected before and after the intervention. 16S rRNA was used for microbiota analysis. Serum untargeted metabolomics used chromatographic analysis with HPLC coupled to a TOF Mass Accuracy.

Results: Differential abundance analysis between the two groups showed changes in family, genus, and species levels, but no significance remained after adjusting by Benjamini–Hochberg. When comparing the changes between baseline and endpoint, Chao 1 (genus level) increased only in the kombucha group (p=0.027). Shannon index and beta diversity by Bray–Curtis dissimilarity did not show any changes after the intervention. In relation to metabolomics, 707 features were found as exclusive of the kombucha group in the ESI+ mode, and 674 features in the ESI- mode. After the exclusion of drugs/toxins, a total of 17 putative metabolites in ESI+ mode and 18 in ESI– were identified only in the kombucha group. Among them, there were compounds derived from fungi (aspergoterpenin D); involved in the glutathione metabolism pathway (5-L-Glutamyl-L-alanine), and with anti-inflammatory effects (ankaflavin).

Conclusion: GTK did not greatly modify intestinal microbiota composition, but it had a relevant impact on the serum metabolome that could positively improve the metabolic health of individuals with excess body weight.