The food and nutrition board of the national academies defines as non-digestible carbohydrates that occur naturally in plant foods.

The food and nutrition board of the national academies defines dietary fiber as non-digestible carbohydrates that occur naturally in plant foods. They also define functional fiber as non-digestible carbohydrate that has been either isolated from natural sources or synthesized in a lab and then added to a food product or supplement. The good source of dietary fiber includes legumes, grains, and vegetables. The health benefits of fiber include reducing the risk of colon cancer; also helps manage diabetes and blood cholesterol levels and reduces risk of hemorrhoids.