A study shows that a diet containing suitable amounts of inulin can influence even the length and other macroscopic characteristics of the intestines. This beneficial action is possible only in the presence of bacteria that digest the fiber, however. Positive alterations in immunity are among the healthy interactions. "In mice that ingested a 10% inulin diet, the gut was larger than in mice that consumed only insoluble fiber [cellulose]. When we analyzed their intestinal tissue, we found more epithelial stem cell proliferation in the animals fed an inulin-rich diet. The epithelium is the layer that separates gut contents from other...