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

Background: Green tea kombucha (GTK) is a fermented beverage with promising health benefits, but few studies proved its impact on human health. Thus, we aimed to investigate the impact of GTK on weight loss, inflammation, and salivary microbiota in individuals with excess body weight. Methods: This is a randomized controlled clinical trial that lasted 10 weeks with two groups of individuals with excess body weight: control (CG; n = 29; caloric restriction) and kombucha (KG; n = 30; caloric restriction + 200 mL GTK). Body composition, anthropometry, saliva, and blood collection were performed in the beginning and end of the intervention. Plasma interleukins were determined by flow cytometry. Salivary microbiota was analyzed by 16S rRNA sequencing. Results: Both groups decreased weight, BMI, and body fat (p < 0.001) after the intervention, but there were no differences between groups. The KG reduced lipid accumulation product (LAP) (p = 0.029). Both groups decreased IL-1β and IL-8, but IL-6 increased in the CG (p = 0.023) compared to the kombucha group. Alpha and beta diversity of salivary microbiota increased in the KG. Moreover, the KG presented lower Bacillota/Bacteroidota ratio (p = 0.028), and BMI was positively associated with the Bacillota phylum. Conclusions: GTK did not enhance weight loss, but it decreased the LAP. GTK helped in the inflammatory profile and induced positive changes in oral microbiota composition.