fiber, dietary, bulky part of food that cannot be broken down by enzymes in the small intestine of the digestive system. Almost all natural fiber comes from plants. Although fiber has little nutritional value, it offers other health benefits. By adding bulk to the diet, fiber prevents constipation, minimizes intestinal disorders, and may serve as an aid in dieting. The benefits of consuming foods high in fiber include lower blood levels of cholesterol and triglycerides. Foods high in fiber include legumes, green, leafy vegetables, whole fruits, and unrefined foods such as bran and sprouted seeds. Fiber is also known as roughage. Robert L. Ory, Grandma Called It Roughage: Fiber Facts and Fallacies (1991).