A new clinical study suggests that a modest daily intake of kombucha—just 200 ml—can lead to significant changes in gut microbial composition, particularly among adults with obesity. Conducted by researchers from the Federal University of Viçosa in Brazil, the study tracked 38 adults over an eight-week period while keeping their diet and physical activity unchanged. The findings, published in The Journal of Nutrition, provide new insight into how kombucha may help foster an internal environment favorable for improved metabolic health, without relying on drastic lifestyle changes.
The trial divided participants into two groups: one of individuals with a normal body mass index (BMI) averaging 21.64 kg/m², and another with individuals categorized as obese, averaging a BMI of 34.47 kg/m². Throughout the eight weeks, each participant consumed a daily dose of black tea kombucha while maintaining their existing routines.
While the study did not explicitly aim to achieve weight loss, the microbial shifts observed point to a healthier internal profile—especially in the obese group. Researchers noted that kombucha consumption increased levels of Akkermansia muciniphila, a bacterium associated with improved insulin sensitivity, lower inflammation, and enhanced gut barrier function. This bacterium plays a critical role in maintaining the intestinal tight junction (TJ) barrier, whose dysfunction is often linked to conditions such as inflammatory bowel disease (IBD).
Alongside Akkermansia, levels of Subdoligranulum also increased in the obese participants. This genus produces butyrate, a short-chain fatty acid that supports better blood sugar control and helps reduce liver fat accumulation. Another positive microbial shift included a rise in Bacteroidota, which assists in the breakdown of proteins and carbohydrates and is considered a beneficial part of a balanced gut ecosystem.
Conversely, the levels of Ruminococcus and Dorea—microbes frequently associated with visceral fat, metabolic dysfunction, and systemic inflammation—were found to decrease in the obese group. According to the researchers, these microbes were initially elevated in the obese cohort but dropped to levels similar to those in the normal-weight group after kombucha consumption.
“A total of 145 phenolic compounds were identified in the kombucha, primarily flavonoids (81%) and phenolic acids (19%),” the researchers reported. These antioxidant compounds are known to play a role in supporting gut health and shaping microbial populations by creating favorable conditions for beneficial bacteria. “Kombucha favored commensal bacteria such as Bacteroidota and Akkermansiaceae, especially in the obese group. Subdoligranulum, a butyrate producer, also increased in the obese group after kombucha consumption. Obesity-associated genera Ruminococcus and Dorea were elevated in the obese group at baseline and reduced after kombucha consumption, becoming similar to the normal weight group.”
The impact of kombucha was not limited to bacteria. The study also recorded changes in the fungal populations in participants’ guts. Notably, reductions in the relative abundance of Rhodotorula, Exophiala, and Candida were observed. These fungi have been associated with obesity and gut inflammation, particularly in individuals consuming a Western-style diet.
“Although the difference was not significant among the groups, the relative abundance of Debaryomycetaceae and Candida decreased after kombucha intake in normal and obese individuals when compared with the same group at the baseline,” the researchers noted. “Debaryomyces has been linked to the Western diet and gastrointestinal inflammation. D. hansenii, a fungus widely used in the food industry, has been linked to mucosal inflammation and Crohn’s disease via CCL5. Candida is part of a healthy microbiota but in high abundance, it has been identified as an opportunistic microorganism, causing a reduction in community diversity, and unbalancing the gut microbiota.”
Rather than introducing external probiotic strains, kombucha appeared to work by promoting conditions that allowed beneficial species already present in the gut to thrive. This sets it apart from many commercial probiotics, which focus on delivering new bacteria to the system.
The microbial changes were more pronounced in the obese group, whose post-intervention gut profiles began to resemble those of the normal-weight group. While this suggests kombucha may help reverse some of the microbiota imbalances associated with obesity, the study authors caution against oversimplification.
“It should be noted that a critical approach is needed when interpreting the role of certain microorganisms in health and disease, because there is no clear consensus in the literature,” the team emphasized. “This requires considering not only the microorganisms themselves but also the complex intra- and interspecies relationships between bacteria and fungi, as indicated by some authors. Those studies have observed positive interactions between bacterial and fungal species, indicating a possible mutual dependence. Conversely, negative correlations suggest a competitive or inhibitory relationship, pointing to the potential for gut fungi to influence bacterial populations and vice versa. Additionally, the broader context of diet and other influencing factors must be considered when evaluating these findings.”
The study does have limitations. It was conducted during the COVID-19 pandemic, which may have inadvertently influenced participant behavior and gut health. Additionally, the absence of a placebo or control group limits the ability to attribute the changes solely to kombucha. Instead, the study compares differences between the normal and obese cohorts before and after the kombucha regimen.
Nonetheless, the findings contribute to the expanding body of research on how gut health can be influenced by small, manageable dietary additions. “Regular consumption of black tea kombucha, rich in phenolic compounds, for eight consecutive weeks, was able to modulate the gut microbiota in individuals with and without obesity,” the study concludes. “Although both groups were impacted, the benefits were interestingly more pronounced in the obese group, as observed by a reduction in obesity-associated microorganisms, such as Ruminococcus and Dorea. Furthermore, kombucha consumption favored beneficial microorganisms related to improved metabolic outcomes in the obese group, such as Akkermansiaceae, Prevotellaceae, and Subdoligranulum.”
While the study does not establish kombucha as a standalone treatment for metabolic disorders or obesity, it offers an accessible avenue for individuals interested in supporting their gut health. The key takeaway is that modest, sustained consumption of kombucha may help create a gut environment more conducive to metabolic balance—without requiring drastic lifestyle overhauls.
Further research, ideally including placebo-controlled trials and longer observation periods, will be needed to fully understand kombucha’s potential and limitations. But as this study shows, even a simple daily habit can play a role in reshaping our internal microbial ecosystems in potentially beneficial ways.
Source: The Journal of Nutrition