Fermented Brown Rice Milk Relieved Bloating and Pain by Boosting Blautia Bacteria

Three weeks of fermented brown rice milk reduced straining, bloating, and abdominal pain in constipation patients more effectively than a matched control drink, according to a double-blind randomized controlled trial published in July 2026. The culprit, or rather the cure, may be a cluster of bacteria in the genus Blautia, three species of which increased significantly in people who drank the intervention beverage. The findings are preliminary, but they add to a growing picture of how specific fermented foods can reshape the gut microbiome in ways that ease real symptoms.

Fermented Brown Rice Milk Targets Specific Constipation Symptoms

The trial enrolled 100 adults with functional constipation, a common gastrointestinal disorder defined by persistent difficulty passing stool in the absence of an identifiable physical cause. Participants were randomly assigned to drink either 500 ml per day of the plant-based milk containing fermented brown rice, or an isocaloric plant protein milk serving as the control. Ninety-nine of the 100 participants completed the full three-week period. Both groups saw improvements over time in complete spontaneous bowel movement (CSBM) rate and bowel movement frequency (BMF), and both reported lower scores on the Gastrointestinal Symptom Rating Scale (GSRS). However, those head-to-head trends were not statistically different between the two groups. Where the fermented brown rice milk pulled ahead was in specific symptoms: straining, bloating, and abdominal pain all improved significantly more in the intervention group than in the control group, with all three comparisons reaching P less than 0.05.

The distinction matters. Many fiber-containing foods improve stool frequency in a general way, but targeting discomfort symptoms like pain and bloating is harder. Probiotics found in fermented foods have previously been shown to reduce gut transit time and modify intestinal microbiota, though evidence for specific symptom relief has been inconsistent. This trial offers a more granular view by pairing symptom data with detailed microbial analysis.

Who Has Constipation and Why the Microbiome Is Central

Functional constipation affects a substantial portion of the global population, generating significant healthcare costs and reducing quality of life. Growing evidence links chronic constipation to alterations in the intestinal microbiota, suggesting that dysbiosis, an imbalance in gut microbial communities, may contribute to both the frequency and the severity of symptoms. The precise mechanisms are still being worked out. Research points to microbial metabolic activities involving bile acids, short-chain fatty acids, and methane production as likely mediators between microbial composition and gut function. That biochemical scaffolding is important context for what this trial found: the intervention did not simply increase bacterial counts broadly; it shifted specific species in a way that tracked with patient-reported improvements.

How Metagenomic Analysis Revealed the Blautia Connection

The researchers used shotgun metagenomics to characterize gut microbial communities before and after the intervention. This method sequences all microbial DNA in a stool sample, offering a higher-resolution picture than older culture-based techniques or 16S rRNA profiling alone. Eight gut microbial species increased in the intervention group over the three weeks. Three of those species belonged to the genus Blautia, a group with known probiotic characteristics and a demonstrated ability to regulate host health. Crucially, the increases in Blautia species were statistically associated with relief of abdominal pain, suggesting a mechanistic link rather than a coincidental shift. The researchers also built machine learning models using gut microbiota features to identify which participants were likely to respond to the intervention, a step that hints at future personalized nutrition applications. The gut microbiome's influence on colonic motility operates through the enteric nervous system and immune pathways, and Blautia-derived signals may be acting along similar routes, though that specific mechanism was not tested here.

Caveats: Primary Outcome Did Not Reach Significance

The headline limitation is straightforward: the trial's primary outcome, the CSBM rate, did not show a statistically significant difference between the intervention and control groups. Both drinks improved bowel movement patterns, which could mean the control plant protein milk was more active than expected, or that three weeks is too short a window to see divergence in that particular metric. The secondary symptom outcomes that did reach significance are meaningful clinically, but a trial powered on a primary outcome that misses its target needs to be interpreted cautiously. The study was conducted in China and registered in the Chinese Clinical Trial Registry; whether the findings generalize to other populations with different baseline microbiomes and diets remains unknown. Three weeks is also a short intervention window; longer follow-up would be needed to understand whether the Blautia increases are sustained and whether symptom relief persists after stopping the beverage.

What Comes Next for Fermented Food and Gut Microbiota Research

The machine learning component of this trial is arguably its most forward-looking element. By identifying gut microbiota features that predict who responds to the intervention, the researchers lay groundwork for matching fermented food products to patients most likely to benefit. That kind of precision approach would require much larger cohorts and external validation, but the proof-of-concept is present here. The Blautia thread is also worth following: these bacteria have appeared in constipation and inflammation research before, and pinning down their metabolic outputs could clarify whether they are a reliable therapeutic target. For now, the trial offers cautious encouragement that a plant-based, fermented milk product can selectively ease some of the most bothersome aspects of functional constipation, straining, bloating, and pain, even when it does not dramatically shift overall bowel frequency.

Evidence rating

EMERGING — 84/100

Caveats:

• The study's primary endpoint — complete spontaneous bowel movement (CSBM) rate — showed no significant difference between the intervention and control groups, meaning the headline constipation benefit did not meet its own pre-specified bar.
• Short 3-week intervention with n=99 completers limits conclusions about durability of microbiome changes.
• Microbiome changes were associated with symptom relief but causality has not been established; the mechanism linking Blautia increases to abdominal pain relief remains proposed, not proven.
• Funding was not disclosed in the available abstract; the commercial nature of the tested product (a branded plant-based milk) cannot be ruled out without full conflict-of-interest disclosure.
• This is a single trial registered in the Chinese Clinical Trial Registry and has not yet been independently replicated.

Double-blind RCT (n=99 completers, 3 weeks). The primary endpoint — complete spontaneous bowel movement rate — did not differ significantly between groups. Secondary symptom scores (straining, bloating, abdominal pain) did favor the intervention. Metagenomic analysis identified increases in three Blautia species associated with symptom relief, but the study establishes association rather than causation, and findings have not yet been independently replicated.

References

1. Amei Tang, Qiuge Cao, Menghan Wang, et al. (2026). The effectiveness of a plant-based milk with fermented brown rice on constipation symptoms via gut microbiota modulation: a double-blind randomized controlled trial. European Journal of Nutrition. https://doi.org/10.1007/s00394-026-04029-0
2. The contributions of gut microbiota and probiotics to gut motility and constipation. NIH. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5529496/
3. Ying Zhao, Yan-Bo Yu (2016). Intestinal microbiota and chronic constipation. SpringerPlus. https://doi.org/10.1186/s40064-016-2821-1
4. Shengsheng Zhang, Ruixin Wang, Danyan Li, Luqing Zhao, Lixin Zhu (2021). Role of gut microbiota in functional constipation. Gastroenterology Report. https://doi.org/10.1093/gastro/goab035
5. Ruili Pan, Linlin Wang, Xiaopeng Xu, et al. (2022). Crosstalk between the Gut Microbiome and Colonic Motility in Chronic Constipation: Potential Mechanisms and Microbiota Modulation. Nutrients. https://doi.org/10.3390/nu14183704