Direct plant consumption maximizes dietary fiber intake

Steps:

• Dietary fiber is indigestible plant material from cell walls, providing bulk in the human diet.
• Fiber remains intact when humans eat plants directly but is mostly broken down or excluded in animal digestion.
• Evaluate pathways: Direct plant-to-human retains fiber; animal intermediaries lose it in meat, eggs, or fish.
• Select option with no animal step for highest fiber yield.

Why A is correct:

• Soybeans are consumed directly by humans, preserving their high insoluble fiber content (e.g., from cellulose), which passes undigested per the definition of dietary fiber.

Why the others are wrong:

• B: Cows ferment grass fiber via rumen bacteria, so beef contains no significant fiber.
• C: Chickens digest maize fiber for energy, leaving poultry and eggs with negligible fiber.
• D: Multiple trophic levels in aquatic chains degrade microscopic plant fiber, resulting in fiber-free fish meat.

Final answer: A