The objective is to investigate some of the basic mechanisms explaining the nutritional and metabolic effects of dietary fiber. Epidemiological evidence has linked a lack of fiber in the diet with several chronic diseases such as disorders of the large intestine, cardiovascular disease, and diabetes mellitus. Recent clinical studies have suggested that sources of dietary fiber can be useful in the management of diabetic and hyperlipidemic patients. In the present proposal the basic mechanisms leading to these alterations in lipid and carbohydrate metabolism and the long term consequences of fiber consumption in an experimental model will be investigated. This objective will be achieved by determining 1) the changes in lipid and apolipoprotein composition of plasma lipoproteins in rats fed guar gum, a source of viscous polysaccharides, and wheat bran for up to 2 years to evaluate the long term hypolipidemic value of fiber, 2) the ability of fiber sources to bind or sequester zinc in the small intestinal contents to understand its potential effects on mineral availability, 3) alterations in the intestinal secretion of apolipoproteins, which contribute to the plasma levels, from the small intestine that are due to consuming various sources of dietary fiber, 4) the ability of various sources of dietary fiber to delay the disappearance of starch from the small intestine and hence influence the glycemic response to a fiber-containing meal, and 5) the postprandial changes in plasma lipids and apolipoproteins in human subjects consuming standardized meals supplemented with fiber sources to investigate the hypothesis that in humans the hyperlipidemic effect of fibers containing viscous polysaccharides is due to slowing the rate of lipid absorption. In view of the interest of fiber as a nutritional component, as a therapeutic agent, and in the health problems which may be associated with consuming a fiber-depleted diet, research is necessary into its effects on metabolism. An understanding of the nutritional and metabolic consequences of consuming fiber will enable us to make knowledgeable recommendations for the consumption of dietary fiber.