In 1956, Surgeon Captain T. L. Cleave propounded much of the basic theory of the importance of unrefined carbohydrates in his paper, The Neglect of Natural Principles in Current Medical Practice (1). Cleave's original "saccharine disease" hypothesis (2,3) was confirmed, refined, and expanded by others, including Burkitt and Trowell (4) and Walker (5). This concept was reexpressed as the dietary fiber hypothesis (4,6) and has two primary statements: (a) A diet rich in foods containing plant cell walls is protective against a wide range of diseases common in Western cultures, including constipation, diverticular disease, colon cancer, heart disease, diabetes, obesity, and gallstones; (b) In some cases, a diet low in these dietary materials may be either causative in certain diseases or may provide conditions in which other factors are more active. Since the early 1970s, dietary fiber has become a topic that has burgeoned from an esoteric interest of a few research laboratories to a subject that has aroused international interest. This growth has been helped by an intense public interest in the potential benefit to be gained by adding fiber to the diet—and may have been helped by the perception that, for once, medicine was saying "do" instead of "don't" (7). This welcomed expansion in the concern with nutritional and medical aspects of dietary fibers has clearly indicated that these materials cannot be considered inert components of the diet. Although the mechanisms of action are not yet completely understood, dietary 208fibers or specific fiber components have already found extensive therapeutic utility in the treatment of several medical disorders or diseases. Among these are simple constipation, symptomology of diverticular disease of the colon, and diabetes mellitus. Whether or not the lack of fiber per se may be responsible, either directly or indirectly, for the variety of diseases expressed in the hypothesis remains to be determined.