Construct a one-sentence explanation suitable for teaching that contrasts the digestion and physiological roles of starch vs fiber.

• A. Starch is indigestible and always causes constipation, whereas fiber is rapidly converted to glucose in the stomach giving immediate energy.
• B. Starch and fiber are identical in composition and function; both are fully digestible and serve as the main sources of fat-soluble vitamins in the diet.
• C. Starch is a type of dietary fat and is absorbed by bile acids, while fiber is a protein that supplies essential amino acids to the colon.
• D. Starch is a digestible plant glucose polymer broken down by human enzymes to provide energy and raise blood glucose, whereas fiber is largely nondigestible plant polysaccharide that resists human enzymes, promotes bowel health, and may be partially fermented by gut microbes to beneficial short-chain fatty acids.

Answer: (D)