The influence of dietary fiber on total oral to anal transit time depends on which factor?

• A. Calorie content
• B. Type and source of fiber
• C. Water content
• D. Protein intake

Answer: (B)

The effect of dietary fiber on total oral-to-anal transit time depends on the fiber’s physical and chemical properties, which are determined by its type and source. Insoluble fibers, like bran, add bulk and stimulate peristalsis, generally speeding transit. Soluble, viscous fibers, such as psyllium or pectin, form gels and slow movement through the gut, which can lengthen transit time. Since different fiber sources vary in soluble vs insoluble content, viscosity, and fermentability, they produce different impacts on overall transit. While hydration and other nutrients can influence stool characteristics, they do not alone dictate how fiber type will alter transit time.