The effects on propionate (a SCFA) were linked to both the compositional shifts in the gut microbiota, and the composition of an individual’s microbiome at the start of the study, reported an international team led by scientists from the University of Alberta.
“These findings constitute a proof-of-concept for the merit of an ecological framework that considers features of the wider gut microbial community for the prediction of metabolic outcomes of dietary fiber fermentation,” they wrote in the journal Microbiome.
“This provides a basis to personalize the use of dietary fiber in nutritional application and to stratify human populations by relevant gut microbiota features to account for the inconsistent health effects in human intervention studies.”
The study suggests that the long-chain, complex arabinoxylan has prebiotic properties, said the researchers. They used an arabinoxylan derived from corn fiber.
A prebiotic is defined as: “A substrate that is selectively utilized by host microorganisms conferring a health benefit” (ISAPP 2017). The ingredients are typically fiber or starch-based components that “feed” the good bacteria in the gut.
The researchers explained that while fiber induce significant changes to the gut microbiota, these effects are highly individualized, “and this variability might have clinical ramifications that could explain the individualized clinical responses”, they wrote.
Despite it being known that the effects differ from one person to the next, this has not received a lot of attention, and “the underlying ecological principles have received little attention”, they said.
Thirty-one overweight and obese adults were recruited to participate in the parallel two-arm, exploratory randomized controlled study. The volunteers were randomly assigned to receive either high-dose arabinoxylan supplements (women at 25 grams per day, and men at 35 g/day) or microcrystalline cellulose, a non-fermentable control.
Results of the six-week study showed that arabinoxylan supplementation produced a global shift in fecal bacterial community composition, and promoted the growth of specific taxa, “including operational taxonomic units related to Bifidobacterium longum, Blautia obeum, and Prevotella copri”.
Increased in fecal propionate concentrations were also reported in the arabinoxylan group.
“From an applied perspective, our findings have implications for the targeted use of arabinoxylan to modulate the gut microbiota for improved health,” they wrote. “Probiotic treatments with B. longum strains have been shown to be health-promoting in a variety of context… The specific enrichment of this species supports the use of arabinoxylan in synbiotic applications with B. longum.”
The increases in P. copri also deserves attention, they said, because the role of this species in human health remains unclear, with some reports suggesting a detrimental effect and other reports indicating benefits associated with improved glucose metabolism and weight loss in people consuming a whole grain-rich diet.
“Prevotella is a genus that has been consistently negatively associated with an industrialized lifestyle,” they wrote. “The reason for this reduction due to industrialization is unknown, but it has been speculated that reduced consumption of dietary fiber rich foods is responsible. The increase of P. copri after supplementing through arabinoxylan supports this hypothesis, as arabinoxylan is a dominant fiber in whole grains, which are reduced in the westernized diet.”
The researchers added: “Overall, our findings suggest that arabinoxylan has prebiotic properties in that it promotes putatively health-related organisms and the production of propionate, making it a promising candidate for the prevention of obesity and associated pathologies, especially if its application is personalized.”
The research was funded by European and Canadian public research grants.
2020, 8, 118, doi: 10.1186/s40168-020-00887-w
“Gut microbiota modulation with long-chain corn bran arabinoxylan in adults with overweight and obesity is linked to an individualized temporal increase in fecal propionate”
Authors: N.K. Nguyen, et al.