Writing in the journal Microbiome, researchers from Université Paris Cité, Georgia State University and Pennsylvania State University revealed that the effects of soluble fibers such as inulin and psyllium on inflammation in the colon depend on individual microbiome compositions in healthy subjects.
“[O]ur observations align with previous studies in mice and humans reporting that the addition of fiber to the diet is a ‘double-edged sword’ capable of promoting or demoting gut health in a manner determined not only by the specific fiber being consumed but also based on an individual’s pre-existing microbiota structure and function,” they reported.
The study adds to emerging evidence suggesting the importance of personalized fiber-based interventions in both inflammatory bowel disease (IBD) patients and healthy individuals.
Compound and context specific
Both animal models and human clinical studies have shown that soluble fibers (the microbiota’s primary source of nourishment) are fermented by intestinal microbes, producing short-chain fatty acids (SCFA) that confer beneficial effects on intestinal and metabolic health.
In contrast, the current study noted that the impacts of fibers on IBD are less clear. Consumption of inulin and psyllium soluble fibers has been associated with health benefits in large epidemiological studies. However, mice studies show that inulin supplementation may exacerbate colitis, while both DSS and T-cell transfer colitis models suggest that psyllium could provide strong protective effects and induce a wholly unique microbiota.
“Hence, the impact of fiber on intestinal health is likely compound- and context-specific, perfectly aligning with the complex observation that while epidemiological studies suggest that consumption of fiber-rich diets correlates with a reduced incidence of IBD, numerous clinical studies suggest that, once the disease is established, some IBD patients experience intolerance to fermentable fiber-rich foods with disease flares,” the researchers wrote.
Study details
To test the hypothesis that the impact of soluble fiber is highly microbiota-dependent and individual-specific, the researchers used a MiniBioReactor Arrays (MBRAs)—an in vitro microbiota modeling system.
They collected fecal samples from six healthy subjects and conducted three independent experiments, with each experiment containing cellulose- (control), inulin- or psyllium-treated chambers, in triplicates for each of the six donors studied, resulting in a total of nine independent MBRA chambers per donor. Fiber-sensitive or fiber-resistant fecal microbiota were then transplanted to germ-free mice to evaluate effects on intestinal inflammation.
“We observed a high level of inter-individual variance in the extent to which microbiotas were altered by exposure to inulin or psyllium,” the researchers reported. “Such responses predicted the extent to which the severity of colitis was altered by select fiber consumption in mice transplanted with these microbiotas.”
More specifically, they noted the possibility that “IBD patients hosting a fiber-resistant microbiota should not refrain from consuming various soluble fibers, while patients with a fiber-sensitive microbiota should carefully consider fiber intake and fiber source as a central actor for disease management”.
Based on the specificity of the microbiota-fiber interactions identified, the study called for further trials using a broader selection of soluble fibers in larger cohorts to better characterize microbiota sensitivity and the mechanism through which this sensitivity promotes or demotes chronic intestinal inflammation.
Source: Microbiome
“Individualized microbiotas dictate the impact of dietary fiber on colitis sensitivity”
doi: 10.1186/s40168-023-01724-6
Authors: Bretin E. Bonazzi