How does fiber contribute to reducing the risk of constipation?

Fiber plays a crucial role in reducing the risk of constipation primarily by adding bulk to stool. When consumed, dietary fiber increases the size and weight of stool and can help it pass more easily through the digestive tract. The bulkier stool stimulates the intestinal walls to contract, promoting regular bowel movements and preventing constipation.

This process is primarily facilitated by soluble and insoluble types of fiber. Insoluble fiber, found in whole grains and vegetables, does not dissolve in water and adds to the bulk, while soluble fiber may absorb water and form a gel-like substance, which also aids in smooth passage through the intestines. Together, they enhance bowel regularity and help to maintain a healthy digestive system.

While the other options involve important aspects of nutrition, they do not directly relate to the mechanism through which fiber alleviates constipation. For example, dissolving in water pertains to soluble fiber's characteristics, but does not specifically address stool bulk. Breaking down sugars relates to digestion and metabolic processes, while lowering cholesterol is a benefit associated with certain types of soluble fiber but does not have a direct connection to preventing constipation.