Most special diets contain one type of fiber to help move bulk through the intestines (nonfermentable). Nonfermentable fiber, such as cellulose, isn’t broken down by the normal bacteria in a cat’s intestines. Instead it passes through the digestive tract, helping other material, such as hair, move along as well. Other special diets contain a combination of nonfermentable fiber and another type of fiber (moderately fermentable). Moderately fermentable fiber, such as beet pulp, helps move bulk and helps provide nourishment to intestinal cells which, in turn, helps maintain intestinal health.