Mice eating a low-fibre diet have a higher risk of bowel infection, thanks to bacteria that normally live in the gut.
Eric Martens at the University of Michigan Medical School in Ann Arbor and Mahesh Desai, now at the Luxembourg Institute of Health, together with their colleagues, compared the effects of fibre-poor and fibre-rich diets in mice that lacked their own bacteria and were given a mix of 14 species of human gut bacteria. These microbes normally consume carbohydrates from dietary fibre, but without these nutrients, the bacteria instead degraded the mucus barrier that lines the intestinal wall.
Thinning of this protective layer (pictured as indicated by white arrows in the right panel; left panel shows normal layer) exposed the intestinal surface to attack by disease-causing bacteria. More than half of the mice eating a low-fibre diet lost at least 20% of their body weight after infection with the pathogen Citrobacter rodentium.