Mice fed beef protein developed more severe colitis than mice fed pea protein, and the difference appeared to be driven by changes in gut bacteria and bile acid metabolism, according to a study published in Cellular and Molecular Gastroenterology and Hepatology.
Researchers from Stony Brook University, the University of North Carolina, Chapel Hill, and Cornell University evaluated diets containing protein isolates from beef, pea, soy, egg white, and casein in several mouse models of inflammatory bowel disease (IBD). The study’s lead author, Simon Gray, is a 2025 AGA Research Scholar Award recipient. Across the models, beef protein was linked to the highest levels of inflammation, while pea protein was linked to the lowest.
The findings may help explain earlier studies that linked red meat consumption to a higher risk of developing IBD and experiencing disease flare-ups. They also suggest that the protein in red meat may play a role in those effects.
The researchers found that beef protein's harmful effects were driven by the gut microbiome. When gut bacteria were eliminated or greatly reduced, beef protein no longer worsened colitis. In addition, transferring gut microbes from beef protein-fed mice to germ-free mice caused the recipients to develop more severe colitis, suggesting that changes in the microbiome played a key role.
In mice without colitis, beef protein changed the composition of the gut microbiome. It reduced levels of Lactobacillus johnsonii and Turicibacter sanguinis while increasing Akkermansia muciniphila. These microbial changes were linked to a thinner and less protective intestinal mucus layer.
Beef protein also changed bile acid patterns in the gut. Mice fed beef protein had higher levels of primary and conjugated bile acids, while mice fed pea protein had higher levels of secondary and unconjugated bile acids. Researchers also found that giving mice taurocholic acid, a conjugated bile acid that was elevated in the beef protein group, made colitis worse, even in mice fed pea protein.
The researchers then examined whether psyllium fiber could offset these effects. Replacing cellulose with psyllium in the beef protein diet reduced inflammation in both chronic and acute colitis models. It also restored populations of bacteria involved in bile acid metabolism and shifted bile acid levels toward a pattern associated with less inflammation.
For practicing physicians, these findings suggest that the type of dietary protein may affect intestinal inflammation by altering the gut microbiome and bile acid metabolism. Although the study was conducted in mice, it provides biological support for dietary approaches that emphasize plant-based proteins and fiber for patients with IBD.
“Collectively, these data suggest that the protein component of red meat may be responsible, in part, for the colitis-promoting effects of this food source and provide insight into dietary factors that may influence IBD severity,” the authors wrote.
The study was supported by the American Pulse Association, National Institutes of Health grants, the Crohn’s & Colitis Foundation Gnotobiotic Facility and institutional funding from Stony Brook University. The authors reported having no relevant disclosures.