Which of the following aids in digestion?

Fiber plays a crucial role in digestion by helping to regulate the body's use of sugars, thereby helping to keep hunger and blood sugar in check. It is a type of carbohydrate that the body cannot digest fully, which means it passes through the digestive system relatively intact. This characteristic is what makes fiber beneficial for digestive health.

Specifically, fiber adds bulk to the stool and aids in the movement of food through the digestive tract, which can help prevent constipation and promote regularity. It also contributes to a healthy gut microbiome by serving as food for beneficial bacteria. Additionally, fiber can slow down the absorption of sugar, leading to better blood sugar management.

While protein, starch, and sugars have roles in nutrition, they do not serve the same specific function in aiding digestion as fiber does. Protein is vital for growth and repair, starch is a significant energy source, and sugars provide quick energy but do not have the digestive benefits associated with fiber.