Effect of Soluble Grain Fiber on Lipoprotein Metabolism

Newman, Rosemary

Abstract

Coronary heart disease is the major cause of death in the USA and other industrialized nations. Elevated serum cholesterol has been identified as a major risk factor for cardiovascular diseases. Dietary intervention has been shown to be a preferred treatment to drugs for lowering serum lipid levels. Soluble dietary fiber has been documented as an effective dietary agent for controlling serum lipoproteins, particularly when used in combination with a fat-modified diet. On component of dietary fiber with a hypocholesterolemic effect is mixed link 1-3, 1-4 beta-glucans, found in oats and barley. Barley is unique among cereal grains for its type and quantity of dietary fiber, particularly the beta-glucans. Certain cultivars of barley contain up to threefold the quantity of beta-glucans as oats. Selective milling of whole barley grain cultivars has provided beta-glucan rich fractions which can be purified and incorporated into foods as a dietary fiber supplement. This work will focus on investigation of the mechanisms of the hypocholesterolemic effects of barley soluble dietary fiber, using the chick, as an animal model. Beta-glucan rich barley fractions will be tested for fat and cholesterol absorption and bile acid absorption, as well as blood levels of short chain fatty acids which are an indication of bacterial digestion of soluble fiber in the intestine. Viscosity of the gut contents will also be correlated with fat digestibility and serum lipid components. Human studies will consist of feeding products containing soluble fiber supplements as part of controlled diets and measuring plasma lipoprotein response. Subjects with elevated serum lipids will be recruited and screened for suitability. Dietary studies will have a minimum of 28 day periods, with a cross over design to compare average US dietary fat intake or American Heart Association fat-modified diets with or without 20 grams of supplementary soluble dietary fiber. Blood samples will be analyzed for total cholesterol, triglycerides, lipoproteins and apoproteins A-1 and A-II.