The term “dietary fiber” is familiar to most Americans. Many people, however, do not fully understand the nature of dietary fiber and its role in a healthful diet. In this report the American Council on Science and Health reviews current scientific knowledge about the role dietary fiber plays in the prevention and treatment of human diseases and explains the potential benefits and risks of increased fiber intake.
What Is Dietary Fiber?
Dietary fiber is that portion of plants that cannot be digested by the nonmicrobial enzymes of the human digestive tract. Fiber consists of a variety of substances, most of which are complex carbohydrates.
It is important to remember that fiber is naturally present only in foods derived from plants—fruits, vegetables, grains and legumes (beans). Foods of animal origin (even “stringy” meats) contain no fiber. Whole grains contain substantially more fiber than refined grains do, because the refining process removes some of the fiber from the grains. As a general rule, the fiber content of whole grains, nuts and legumes is higher than that of refined grains, fruits and vegetables other than legumes.