Many diseases common in and characteristic of modern western civilization have been shown to be related to the amount of time necessary for the passage of intestinal content through the alimentary tract, and to the bulk and consistency of stools. These factors have in turn been shown to be greatly influenced by the fiber content of the diet and by the amount of cereal fiber in particular.
Mechanisms are postulated whereby these changes in gastrointestinal behavior could in part explain the occurrence of such common disorders as ischemic heart disease, appendicitis, diverticular disease, gallbladder disease, varicose veins, deep vein thrombosis, hiatus hernia, and tumors of the large bowel.
Calorie intake, speed of passage through the intestine, levels of intracolonic pressures, number and type fecal bacteria, as well as levels of serum cholesterol and changes in bile-salt metabolism have all been shown to be related to the amount of dietary fiber consumed.
(JAMA 229:1068-1074, 1974)
Burkitt DP, Walker ARP, Painter NS. Dietary Fiber and Disease. JAMA. 1974;229(8):1068-1074. doi:10.1001/jama.1974.03230460018013