The editors have designed this book to serve both as a textbook on fiber in nutrition and, we hope, as the first complete reference on the subject. For the past 25 years, the study of plant fibers and their effect on human physiology has generally been relegated to a low-priority status. Recently, however, this area of research has enjoyed a renaissance unparalleled in the history of the food and nutritional sciences, a reawakening which has occurred primarily as a result of epidemiology reports that suggested a positive relationship between plant fiber ingestion and health. As interest among the scientific community increased and new research programs were initiated to test objectively the epidemiological hypotheses, major gaps in the fundamental pool of knowledge became apparent. To compound the difficulty, scientists often did not agree upon what "fiber" is. Some investigators restricted their definition to the structural polymers of the plant, while others expanded theirs to include the entire plant cell wall with all its fibrous and associated nonfibrous substances. As a result, research that was performed and reported frequently only obscured the issue still further; at best it exposed whole new areas of ignorance in a field once considered too uninteresting to pursue. Despite voluminous research, scientists generally have still not been able to identify with certainty the specific component(s) of the plant cell-wall system that causes the various observed physiological effects. In fact, they do not yet agree upon the nomenclatures involved.