The phrase "of dietary fiber" refers to something that contains or is made up of dietary fiber. Dietary fiber, also known as roughage, is a type of carbohydrate that is found in plant-based foods such as fruits, vegetables, legumes and whole grains. It is an essential part of a healthy diet because it helps to promote proper digestion by adding bulk to the stool and preventing constipation. When something is described as "of dietary fiber," it means that it contains enough fiber to be beneficial for maintaining good bowel health.