Final answer:
Dietary fiber is defined as nondigestible plant polysaccharides, components of plants that can't be digested by human enzymes, aiding in digestion and health without providing energy.
Step-by-step explanation:
Dietary fiber is best defined as c. nondigestible plant polysaccharides. This component of plant-derived food cannot be broken down by human digestive enzymes. It consists of substances like cellulose, resistant starch, resistant dextrins, inulin, lignins, chitins, pectins, beta-glucans, and oligosaccharides. Unlike other carbohydrates, fiber provides no energy but it plays a crucial role in maintaining a healthy gastrointestinal tract.
For example, insoluble fiber does not dissolve in water but promotes the movement of material through the digestive system. This helps in preventing constipation and reducing the absorption of unhealthy substances like cholesterol, decreasing the risk of colon cancer.