A small daily dose of kombucha made from black tea has been shown to meaningfully reshape the gut microbiome in adults – particularly those with obesity – without any dietary changes. And, importantly, the gut "makeover" boosts beneficial bacteria that play a big role in fighting inflammation and strengthening metabolic processes.
In a first-of-its-kind clinical study, researchers from the Federal University of Viçosa in Brazil tracked 38 adults (21 normal weight, 17 with obesity) over eight weeks as they consumed 200 ml of kombucha every day. Participants kept their regular diets and exercise routines unchanged, in order to isolate the potential benefits of the fermented beverage.
And while the study was not aimed at weight loss, the gut bacteria told a different story of health – and set the participants up to better achieve weight loss goals.
"To the best of our knowledge, there is no clinical trial that has investigated the impact of regular kombucha consumption on the gut microbiota of humans, despite many companies claiming kombucha is a probiotic beverage," the researchers wrote.
In the study, the participants were separated into the two groups: The "normal weight" cohort (mean BMI = 21.64 kg/m2) and the "obese" cohort (mean BMI = 34.47 kg/m2).
Following the eight-week intervention, scientists analyzed gut makeup and made some surprising discoveries. The microbial changes observed, particularly in the obese group, mimicked those seen in people with improved blood sugar control and lower inflammation. And while the study didn’t measure long-term outcomes, it adds to growing evidence that the microbiome can be "hacked" for health, without crash diets or massive lifestyle changes.
The researchers discovered that, across the board, there were increased levels of Akkermansia muciniphila, a bacterium linked to lower inflammation, better insulin sensitivity and a more robust gut lining wall. If compromised, this "wall," known as the intestinal tight junction (TJ) barrier, can trigger inflammatory bowel disease (IBD) and other gut-related inflammatory conditions.
The participants also saw a rise in bugs belonging to the Subdoligranulum genus. Bacteria in this group produce the beneficial short-chain fatty acid butyrate, which is linked to better blood sugar control and reduced liver fat. Similarly, a rise in Bacteroidota microbes, a group that helps break down carbohydrates and proteins, was also gauged.
And, particularly in the obese cohort, Ruminococcus and Dorea numbers were down, which is a good thing – elevated levels of these have been consistently linked to visceral fat, inflammation, and metabolic disease.
"A total of 145 phenolic compounds were identified in the kombucha, primarily flavonoids (81%) and phenolic acids (19%)," the researchers noted in the study. "Kombucha favored commensal bacteria such as Bacteroidota and Akkermanciaceae, 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 kombucha regimen also changed the makeup of fungal content in the gut, with Less Rhodotorula, Exophiala and Candida – all fungi associated with obesity, gut inflammation and consuming a Western 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 scientists observed. "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. Studies show a relationship between Candida spp. and the Western diet, which, in turn, is related to the development of obesity and its associated comorbidities."
While many probiotics focus on adding bacteria to the microbiome, kombucha appeared to create a more friendly environment for beneficial species already in the gut to flourish, especially those that thrive on antioxidant-rich polyphenols.
The microbial changes were more significant in the obese cohort – and, after the eighth week, these participants had gut profiles that resembled those of the "normal weight" group.
Of course, this isn't the first study that has linked kombucha to more efficient metabolic function and even how the gut deals with fat and promotes insulin sensitivity.
Interestingly, this study also highlights an important aspect of our microbiome we (and researchers) can overlook when thinking about gut health. Our gut's bugs are not independent actors where one species is good and another is bad; it's more like any ecosystem, requiring balance for optimal function.
"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 researchers noted. "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 isn't without other limitations. While participants weren't instructed to make changes to their diet, the study was conducted during the pandemic, which may have had an impact. And, without a control group (no kombucha over those eight weeks), the study merely compares different weight cohorts.
Nonetheless, it does show that small changes, such as downing a small cup of kombucha a day, can press a "reset" button that boosts important commensal microbes that, overall, produces an environment beneficial to metabolic function.
"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 researchers concluded. "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."
The research was published in The Journal of Nutrition.
Source: Federal University of Viçosa via The Journal of Nutrition
