Mice fed beef protein developed the worst colitis in a new study. Mice fed pea protein developed the mildest. The bottom line from the research team: the type of protein in a diet can change how severe bowel inflammation gets, and the gut’s bacteria seem to be the go-between.
The work appeared in Cellular and Molecular Gastroenterology and Hepatology. Researchers from Stony Brook University, the University of North Carolina at Chapel Hill and Cornell University tested diets built on protein isolates from beef, pea, soy, egg white and casein. They ran them through several mouse models of inflammatory bowel disease (IBD). Lead author Simon Gray is a 2025 AGA Research Scholar Award recipient.
The ranking held across the models. Beef sat at the top for inflammation, pea at the bottom.
The microbiome did the damage
When the team wiped out or sharply reduced the animals’ gut bacteria, beef protein stopped making colitis worse. Then they moved microbes from beef-fed mice into germ-free mice. Those recipients developed more severe colitis too.
In mice that did not have colitis, beef protein still reshaped the microbial community. Levels of Lactobacillus johnsonii and Turicibacter sanguinis fell, while Akkermansia muciniphila rose. Those shifts went along with a thinner, less protective mucus layer lining the intestine.
Bile acids
Bile acid patterns differed as well. Beef-fed mice had more primary and conjugated bile acids. Pea-fed mice had more secondary and unconjugated ones. The researchers then gave mice taurocholic acid, a conjugated bile acid that was elevated in the beef group, and colitis got worse. That happened even in mice eating pea protein.
Fiber made a difference. Swapping cellulose for psyllium in the beef diet cut inflammation in both chronic and acute colitis models. It also brought back bacteria involved in bile acid metabolism and moved bile acid levels toward a pattern linked with less inflammation.
What it may explain
Earlier studies tied red meat consumption to a higher risk of developing IBD and to flare-ups. The new results suggest the protein in red meat may play a part in that.
“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 work was done in mice, so it does not settle what people with IBD should eat. It does give biological support to diets that lean on plant proteins and fiber.
Funding came from the American Pulse Association, National Institutes of Health grants, the Crohn’s & Colitis Foundation Gnotobiotic Facility and Stony Brook University. The authors reported no relevant disclosures.
