What happens to dietary fiber that is not degraded or fermented in the colon?

• A. Increases stool bulk and weight. Unfermented fiber in the colon creates a gel which holds water, increasing stool water content and softening stool.
• B. Is completely digested by colon enzymes
• C. Is excreted unchanged with no effect on stool
• D. Always causes diarrhea

Answer: (A)

Unfermented dietary fiber that reaches the colon acts as ballast, increasing stool bulk. It isn’t broken down by colon enzymes, so it remains intact and can hold onto water. This water-holding capacity, sometimes through gel formation by soluble fibers, adds mass to the stool and raises its water content, which softens the stool and makes it easier to pass. Because it contributes to stool volume and softness, it is excreted with the feces and does have a tangible effect on stool form. It doesn’t always cause diarrhea; in fact, adequate fiber generally supports regular, well-formed stools, though a rapid or excessive increase can temporarily loosen stools for some people.