Study finds wheat fiber digested by gut bacteria produces IBS-relieving metabolites in mice

A diet enriched with wheat fiber — absent in highly refined carbs like white breads — was able to protect mice from intestinal inflammation, according to new research. The study found that when intestinal bacteria metabolized wheat fiber, they generated bioactive anti-inflammatory metabolites, such as polyphenols.

These metabolites reprogrammed intestinal immune cells to suppress inflammation, protecting mice from developing acute and chronic intestinal inflammation, the study authors highlight.

Translating these findings to humans, the researchers suggest that choosing whole wheat breads, pastas, and other flour-based products, rather than white versions, may reduce people’s risk for developing inflammatory bowel disease (IBD). 

“These findings support the hypothesis that the widespread adoption of bran removal in generating wheat-based foods has contributed to increased incidence of chronic inflammatory diseases,” says senior author Andrew Gewirtz, professor in the Institute for Biomedical Sciences (IBMS) at Georgia State, US. 

“Furthermore, they suggest that incorporating wheat fiber into processed foods may make them healthier.”

Chemistry of dietary fibers

The research, published in Mucosal Immunology, helps explain why the incidence of IBD has increased and suggests that eating whole wheat foods may reduce one’s risk of developing it.

“The chemistry of dietary fibers can be pretty complicated,” says Seong-eun Kim, first author of the study, a recent IBMS Ph.D. graduate and now a postdoctoral fellow at Weill Cornell Medicine, US. 

The wheat fiber caused a shift in the immune response, by reducing the number of aggressive inflammatory cells.“But intestinal bacteria are quite good at metabolizing them, and the immune system is a major beneficiary.”

In the trial, the researchers fed mice either a low-fiber or a wheat-fiber-enriched diet before inducing a condition similar to colitis. IBD is one of the causes of this inflammation of the inner lining of the colon.

They found that mice on the low-fiber diet suffered from significant weight loss and high markers of biological stress, while those eating wheat fiber remained much healthier with longer colons and less tissue damage. 

On a cellular level, the wheat fiber caused a shift in the immune response, by reducing the number of aggressive inflammatory cells and increasing the presence of regulatory cells that help calm the immune system. Overall, these results support that adding wheat fiber to the diet can help protect against severe gut inflammation.

Feeding good bacteria

The researchers also found that a wheat-fiber diet impacted the composition of gut bacteria in mice, notably increasing certain beneficial species like Clostridium ruminantium and Akkermansia muciniphilia. 

However, they discovered that wheat fiber’s protective effect disappeared when the mice lacked a specific genetic element called CNS1, which is necessary for these immune cells to develop.

Without the ability to produce these specific regulatory cells, the wheat fiber could no longer prevent weight loss or intestinal damage, supporting that fiber protects the gut by actively training the immune system to stay calm.

Fiber in focus

These recommendations build on evidence that consuming plant-based foods naturally rich in fiber can support good gut health. Various animal trials also show that enriching diets with fiber promotes beneficial health outcomes, the study authors add.

Wheat fiber performs release bound polyphenols after being digested by gut bacteria.However, they note that these studies largely focused on fibers, which have not historically been a major component of diets in the West. For example, using psyllium, derived from plantago seeds, and inulin, derived from chicory root. 

“Thus, the observation that wheat fiber, historically abundant in Western diets, conferred such benefits is especially relevant to appreciating the importance of dietary fiber on gut health,” they highlight.

Furthermore, they say that the way wheat fiber performs is highly distinct from other fibers. Specifically, it did not act by raising short-chain fatty acids, as soluble fibers do, but by releasing bound polyphenols after being digested by gut bacteria. 

Supporting this, the scientists found that wheat fiber only benefitted mice that had a microbiota capable of catabolizing wheat fiber to release polyphenols.

Ultra-processed food movement

Changes in food production, especially the increased use of highly refined wheat products, have reduced dietary consumption of wheat fiber, potentially contributing to the increased prevalence of IBD. 

Wheat fiber is but one of many fibers that are usually not consumed in adequate amounts in developed countries where most people don’t meet the recommendations of health organizations to consume a minimum of 25 to 38 g of fiber per day. 

“Indeed, the more we study dietary fibers, the more we appreciate that they are highly diverse compounds with fibers from distinct plants having distinct health-promoting impacts,” says Gewirtz. 

“Better understanding of these molecules should ultimately enable production of healthier processed foods, but, meanwhile, choosing whole wheat and whole grain breads and having one’s diet include an assortment of fruits and vegetables seems like a good idea.”

In other fiber-forward research, a recent study, partly funded by ingredient supplier Tate & Lyle, revealed that daily soluble corn fiber “significantly improves” cognition and focus in healthy middle-aged and older adults, boosting gut bacteria that may support brain function.

Among relevant product innovation highlights, Momentous launched Fiber+, a triple-action fiber supplement designed to go beyond digestion and to support gut health, metabolic balance, and a whole-body recovery. The company says it leverages the latest science on fermentable fibers, resistant starch, and the production of short-chain fatty acids.