Dietary Fibre - A Component of Food

Dietary fibre is now recognized as a vital component of good daily nutrition, yet its properties and specific role in the digestive system are still being investigated. The involvement of government agencies, the food industry and health professionals - as well as public interest - make this global overview, Dietary Fibre - A Component of Food, an important contribution to the literature on the subject. The cooperation of experts from different research centers and their peer review of each other's papers enhance the value of the book, since it presents consolidated views and objective assessments on such key issues as fibre analysis and mineral bioavailability. The seventeen chapters are grouped into three sections. The background papers deal with biochemical and analytical characteristics: e.g. the physico-chemical properties of food polysaccharides and bacterial fermentation in the colon. The papers on physiological effects deal with the physiological function of dietary fibre throughout the gastrointestinal tract: its influence on protein, lipid and carbohydrate digestion and absorption and its role in bile acid metabolism and faecal bulking. The third section of papers focuses on the prevention and treatment of disease: gastrointestinal disorders, obesity, diabetes mellitus, and hyperlipidemias.

Contenu

Section I. Background Papers.- 1. The Dietary Fibre Hypothesis: A Historical Perspective.- Developments in the Chemistry and Analysis of Food Carbohydrates: Early Studies on the Chemistry of Foods.- Concerns about the Energy Value of Foods.- Studies on the Chemistry of Plant Cell Walls.- Nutritional Studies on Food Carbohydrates.- The Impact of New Techniques on the Study of Carbohydrates.- The Energy Values of Carbohydrates in the Human Diet.- Studies on the Analysis of Fibre.- Dietary Fibre as a Protective Component of the Diet.- The Dietary Fibre Hypothesis Emerges.- Initial Responses to the Hypothesis.- Major Themes in the Initial Development of the Dietary Fibre Hypothesis.- Definition and Analysis.- Studies with Isolated Polysaccharides.- Dietary Fibre as a Source of Energy.- Mechanism of Faecal Bulking.- The Status of the Dietary Fibre Hypothesis.- Commentary.- 2. Physico-chemical Properties of Food Plant Cell Walls.- Ion-Exchange Properties.- The Ionic Groups Associated with Fibres.- Methods of Cation-Exchange Capacity Determination.- The Cation-Exchange Capacity Values.- Determination of pK.- Hydration Properties.- Hydration Properties of Polysaccharides.- Methods for the Determination of Hydration Characteristics.- Variations of the Hydration Value.- Examples of Hydration Value.- Adsorption of Organic Molecules.- Effect of Processing.- Grinding.- Chemical Treatments.- Heat Treatment.- Conclusions.- 3. Physico-chemical Properties of Food Polysaccharides.- Structure and Shape of Polysaccharide Chains.- Order and Disorder.- Inter-residue Linkage Patterns and Ordered Packing.- Hydrated Networks.- Polysaccharide "Weak Gels".- Hydrodynamic Volume of Disordered Polysaccharide Chains.- Coil Overlap and Entanglement.- Shear-Rate Dependence of Viscosity.- Implications for Digesta Viscosity.- Transport and Release of Nutrients.- Susceptibility to Digestive Enzymes and Colonic Fermentation.- Conclusions.- Commentary.- 4. Dietary Fibre Analysis.- Classification of Carbohydrates in Foods as Related to Dietary Fibre Analysis.- Principal Criteria for Classification.- Degree of Polymerisation.- Classification of the Polysaccharides.- Recommendations for Nomenclature for use in the Classification of Carbohydrates in Nutritional Studies.- The Definition of Dietary Fibre: A Determinant of Analytical Strategy.- Main Features of Analytical Strategies.- Implications for the Choice of Analytical Methods for the Carbohydrates in Foods.- Criteria for the Choice of Method: The Conflict Between the Requirements of Research and Regulation.- Development of Crude Fibre, Detergent Fibre and Enzymatic Methods.- Crude Fibre.- Detergent Fibre Methods.- Enzymatic Methods.- The Method of Asp et al.- The AOAC Method.- The Various Steps in Enzymatic Gravimetric Methods.- Comparison of Methods.- Other Current Gravimetric Methods.- The Southgate Method for Unavailable Carbohydrates.- Principles.- Performance.- Limitations.- Analysis of Individual Components of Dietary Fibre.- Determination and Chemical Characterisation of Total Dietary Fibre by the Uppsala Methodology.- Analysis and Characterisation of Soluble and Insoluble Dietary Fibre.- Main Features of the Method of Englyst et al..- Alternatives for the Determination of Dietary Fibre Constituents.- Collaborative Studies.- Studies under Review and Performance Criteria.- Total Dietary Fibre with Gravimetric Methods.- Non-starch Polysaccharides with the Englyst Procedures.- Separate Measurement of Insoluble and Soluble Dietary Fibre.- Inter-method Comparisons.- Summary and Conclusions.- Note Added in Proof.- The MAFFIV Study.- The AOAC Method.- Commentary.- 5. Gastro-intestinal Physiology and Function.- How Do Non-starch Polysaccharides Reduce Absorption of Nutrients in the Small Intestine?.- How Does Increasing the Viscosity of Gastro-intestinal Contents Delay Absorption?.- Unresolved Issues.- Can Non-starch Polysaccharides Reduce Absorption by Mechanisms Other than Increasing the Viscosity of Gastro-intestinal Contents?.- Effects on the Colon.- Increased Stool Output.- Transit Time.- Laxative Action of Sequestered Bile Acids and Fatty Acids.- Direct Irritant Effect of Particles.- Gas Formation.- How does the Colon Adapt to Fibre?.- 6. Bacterial Fermentation in the Colon and Its Measurement.- Fermentation.- Colonic Bacteria.- Carbohydrate Fermentation by Gut Bacteria.- Dietary Fibre.- Oligosaccharides.- Resistant Starch.- Mucins and Mucopolysaccharide.- Enzymes Involved in Polysaccharide Degradation.- Fermentation Products.- Short Chain Fatty Acids.- Products of Protein and Amino Acid Degradation.- Gaseous Products.- Measurement of Colonic Fermentation In Vivo.- Human Models.- Patients with Colostomies.- Faecal Analysis.- Animal Models.- Measurement of Colonic Fermentation In Vitro.- Static In Vitro Systems.- Continuous and Semi-continuous Culture Systems.- Studies of Carbohydrate Fermentation.- Conclusions.- Commentary.- 7. Metabolism and Utilisation of Short Chain Fatty Acids Produced by Colonic Fermentation.- Background.- Metabolism of SCFA by the Digestive Tract.- Comparison of SCFA and Glucose Absorption.- Hepatic Metabolism of SCFA.- Acetate Metabolism.- Propionate Metabolism.- Butyrate Metabolism.- Extrasplanchnic Metabolism of Acetate.- SCFA and Lipid Metabolism.- Energy Aspects.- Conclusion.- Commentary.- Section II. Physiological Effects.- 8. The Influence of Dietary Fibre on Protein Digestion and Utilisation.- Experiments with Rats.- Conclusion from Experiments with Rats.- Experiments with Pigs.- Conclusion from Experiments with Pigs.- Experiments with Humans.- Conclusion from Experiments with Humans.- General Conclusion.- 9. The Influence of Dietary Fibre on Lipid Digestion and Absorption.- Digestion and Absorption of Dietary Fat.- Inhibition of Lipolytic Activity.- Formation and Composition of Micelles.- Effects of Fibre on Intraluminal Lipid Transport.- The Cellular Phase: Adaptation to Prolonged Fibre Intake.- Conclusions.- Commentary.- 10. The Influence of Dietary Fibre on Carbohydrate Digestion and Absorption.- Acute Effects of Dietary Fibre on Factors Affecting Digestion and Absorption of Carbohydrates.- Influence of Dietary Fibres on Gastric Emptying.- Influence of Dietary Fibres on Small Intestinal Digestion and Absorption.- Chronic Effects of Dietary Fibre on Factors Affecting Digestion and Absorption of Carbohydrates.- Conclusion.- Commentary.- 11. The Influence of Dietary Fibre on Mineral Absorption and Utilisation.- Methodological Considerations in Studies on Mineral Absorption in Humans.- Effects of Fibre and Fibre-Associated Compounds on Mineral Absorption in Humans.- Effect of Non-s…