Dietary fibre, or roughage, is important even though it is not digested because it
- A. supplies energy slowly over several hours
- B. adds bulk that stimulates peristalsis and prevents constipation
- C. is absorbed by the villi as cellulose
- D. provides the essential amino acids
Explanation
Humans have no cellulase, so fibre passes through unchanged, but its bulk holds water and stretches the gut wall, which keeps peristalsis regular and shortens the time waste stays in the colon. Diets low in fibre are linked with constipation, piles and cancer of the colon. Because it is not broken down, fibre supplies no energy and no amino acids.
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