Researchers have discovered that women with the mixed type of irritable bowel syndrome experience significant changes in their gut microbiome depending on whether they are going through periods of constipation or diarrhoea. This shift could explain the recurring and alternating symptoms that define the condition, often referred to as IBS-M.
A study conducted at the Medical University of Lodz examined the gut bacteria of 30 women diagnosed with IBS-M over several months. The women were closely monitored through dietary assessments, breath tests, urine metabolite analysis, and advanced genetic profiling of their gut microbiota. The research, published in the journal Biomedicines, aimed to explore how the composition and metabolic activity of gut bacteria fluctuates during different phases of the disorder.
While the overall level of gut dysbiosis, a term used to describe microbial imbalance, remained consistent between the constipation and diarrhoeal periods, the diversity of bacteria increased significantly during diarrhoea. This diversity was measured using the Shannon index, a common tool used in ecological studies to assess microbial richness.
Notably, beneficial bacteria such as Bifidobacterium and Lactobacillus were found to decrease during diarrhoea. These strains are widely recognised for their role in promoting digestive health. Conversely, levels of Escherichia coli and Clostridium spp. showed a rise. The presence of these bacteria during diarrhoea correlated with elevated levels of hydrogen and ammonia in patients’ breath, while methane levels declined.
The study also examined urinary markers associated with bacterial metabolism. Levels of hippuric acid and indican, compounds that indicate protein fermentation by gut bacteria, dropped during diarrhoea. These chemical markers serve as indirect evidence of changes in bacterial activity, supporting the broader findings about shifts in microbial function.
Despite the persistence of dysbiosis across both phases of IBS-M, the profile of the bacteria involved altered significantly. This suggests that the symptom swings characteristic of IBS-M are linked not simply to the presence of microbial imbalance but to the specific composition and metabolic patterns of the microbiome at any given time.
The findings provide further support for the emerging view that irritable bowel syndrome may be, at least in part, a disorder of the gut microbiota. Treatments aimed at restoring microbial balance, such as targeted probiotic or dietary interventions, could be refined in the future to address specific symptom phases.
The study was limited to women between the ages of 28 and 47 and did not investigate hormonal influences on the microbiome. However, researchers ensured that diet and medication use were strictly controlled throughout the study to minimise other confounding factors.
This research highlights the potential value of personalised treatment approaches in IBS-M that take into account microbial profiles, as well as the need for more dynamic and responsive therapeutic strategies. While many questions remain, the evidence is mounting that the gut microbiome is not just a passive player in digestive health, but a key driver of symptom variation in chronic gastrointestinal disorders.
