Enriching the diet with wheat fiber protects mice from intestinal inflammation, according to a study published by researchers at the Institute for Biomedical Sciences (IBMS) at the University of Georgia. The finding explains why the incidence of inflammatory bowel disease (IBD) has increased and suggests that eating whole grains may reduce the risk of developing it.
The work, which refers to two research papers – in journals Scientific progress and mucosal immunology – investigated the effect of wheat fiber, which is present in wholemeal and wholemeal bread but mostly absent from “white breads” and other products made from refined flours.
The researchers found that the metabolism of wheat fiber by intestinal bacteria produced bioactive anti-inflammatory metabolites, including polyphenols, which reprogrammed cells of the intestinal immune system to suppress inflammation, protecting the mice from developing acute and chronic intestinal inflammation.
Changes in food production, especially the increased use of highly processed wheat products, have reduced dietary consumption of wheat fiber, potentially contributing to the increased prevalence of IBD. The findings, if true in humans, suggest that choosing wholemeal bread, pasta and other flour-based products instead of white versions may reduce the risk of IBD. Additionally, studies show that adding wheat fiber to processed foods can also provide this benefit.
Wheat fiber is just one of many fibers that are often not consumed in sufficient amounts in developed countries. Indeed, most people in developed countries do not meet the recommendations of health organizations to consume at least 25 to 38 grams of fiber per day. These recommendations are based on evidence that eating plant foods, naturally high in fiber, is associated with good health and a number of animal studies showing that dietary fiber enrichment promotes beneficial health outcomes.
However, such studies have largely focused on fibers such as psyllium, derived from Plantago seeds, and inulin, derived from chicory root, which have not historically been an important component of the Western diet. Thus, the observation that wheat fiber, historically abundant in Western diets, conferred such benefits is particularly important in appreciating the importance of dietary fiber in gut health. In addition, the mechanism by which wheat fiber works is very different from other fibers. Specifically, wheat fiber did not act by increasing short-chain fatty acids, as soluble fiber does, but by releasing bound polyphenols when digested by gut bacteria. Indeed, wheat fiber provided benefit to mice only when they contained a microflora capable of digesting wheat fiber to release polyphenols.
These findings support the hypothesis that the widespread adoption of bran removal in wheat-based food production has contributed to the increased incidence of chronic inflammatory diseases. In addition, they suggest that incorporating wheat fiber into processed foods can make them healthier.”
Andrew T. Gewirtz, senior author of the study and Regents Professor at the Institute of Biomedical Sciences at Georgia State
“The chemistry of dietary fiber can be quite complex,” said Seong-eun G. Kim (Ph.D. ’25), the study’s first author, a recent IBMS Ph.D. graduate and now a postdoctoral fellow at Weill Cornell Medicine. “But gut bacteria are pretty good at their metabolism, and the immune system is a major beneficiary.”
“Indeed, the more we study dietary fiber, the more we appreciate that it is very different compounds with fiber from different plants that have distinct health-promoting effects,” Gewirtz added. “A better understanding of these molecules should eventually allow for healthier processed foods, but in the meantime, choosing wholemeal and wholemeal bread and eating a variety of fruits and vegetables seems like a good idea.”
Additional Science Advances study authors include Rachael Ott, Alexis Bretin, Hirohito Abo, Yanling Wang, Yadong Wang and Vu L. Ngo of the Institute of Biomedical Sciences at Georgia State. Shawn Winer of the University of Toronto. Daniel A. Winer of the University of Toronto, Buck Institute for Research on Aging and Toronto General Hospital Research Institute (TGHRI), University Health Network. Lavanya Reddivari of Purdue University; Stacey L. Heaver and Ruth E. Ley of the Max Planck Institute for Biology. and Michael Pellizzon of Research Diets Inc.
The study was funded by the National Institutes of Health (NIH) and a Crohn’s and Colitis Foundation Research Fellowship Award.
