National Academy of Sports Medicine (NASM) Certified Sports Nutrition Coach Practice Test 2025 - Free NASM Nutrition Practice Questions and Study Guide

Soluble fiber is the type of dietary fiber that dissolves in water. When soluble fiber comes into contact with water, it forms a gel-like substance, which can help to slow down digestion and promote feelings of fullness. This type of fiber is beneficial for regulating blood sugar levels, lowering cholesterol, and supporting heart health. Foods that are high in soluble fiber include oats, legumes, apples, and citrus fruits.

In contrast to soluble fiber, insoluble fiber does not dissolve in water. It adds bulk to the stool and helps to promote regular bowel movements, which is essential for digestive health. Cellulose, which is a form of insoluble fiber, is primarily found in the cell walls of plants and is not water-soluble. Starch is a carbohydrate that serves as a source of energy but does not fit the definition of fiber as it does not have the same benefits associated with soluble or insoluble fiber. Therefore, the clear choice for the type of dietary fiber that dissolves in water is soluble fiber.