Dietary fiber has been a topic of considerable interest among nutritionists and clinicians for the past 50 years. Many studies on fiber have concentrated on fiber isolates, resulting in findings that have ignored fiber as a component of fruits, vegetables, nuts, cereals, and legumes in the general diet. The principle actions of fiber are to alter the nature of the contents of the gastrointestinal tract and to modify the absorption of other nutrients and chemicals. Fiber is but one component of plant food, and to neglect the other components--be they proteins, lipids, vitamins, minerals, antioxidants, or the secondary metabolites--is to seriously limit our understanding. Much of the effort expended in defining fiber and studying the fiber isolate would have been better focused using this whole-plant-food approach. Greater progress in our understanding of the relevance of fiber in the etiology of disease would have been achieved if a more holistic approach had been followed.