ABSTRACT
Overview ........................................................................................................................................ 198 Classification .................................................................................................................................. 198 Structure and Nomenclature .......................................................................................................... 198
Monosaccharides ..................................................................................................................... 198 Stereoisomeric Forms ......................................................................................................... 200 Anomeric Forms ................................................................................................................ 203
Oligosaccharides ..................................................................................................................... 204 Disaccharides ..................................................................................................................... 205 Polysaccharides .................................................................................................................. 206
Storage Polysaccharides ................................................................................................ 206 Structural Polysaccharides ............................................................................................ 207 Mucopolysaccharides .................................................................................................... 208
Sources of Carbohydrate ................................................................................................................ 208 Digestion and Absorption .............................................................................................................. 211 Metabolism ..................................................................................................................................... 213
Overview ................................................................................................................................. 213 Glycolysis ................................................................................................................................ 214 Hexose Monophosphate Shunt ............................................................................................... 217 Interconversion of Dietary Sugars .......................................................................................... 218
Fructose .............................................................................................................................. 218 Galactose ............................................................................................................................ 220 Mannose ............................................................................................................................. 221
Glycogenesis and Glycogenolysis .......................................................................................... 221 Gluconeogenesis ..................................................................................................................... 226
Cori and Alanine Cycles .................................................................................................... 226 Glucose Homeostasis .............................................................................................................. 230
Abnormalities in the Regulation of Glucose Homeostasis: Diabetes Mellitus ............................ 233 Consequences of Insulin Deficiency ...................................................................................... 236
Pancreatic ~ Islet Cell Failure ........................................................................................... 238 Autoimmune Disease ......................................................................................................... 238 Diabetes Secondary to Viral Infections ............................................................................. 240 Genetic Errors in Insulin Structure .................................................................................... 241
Target Tissue Disease ............................................................................................................. 242 Mobile Glucose Transporters ............................................................................................. 244 Diabetes Due to a Mitochondrial Genomic Mutation ....................................................... 245
Other Health Concerns in Carbohydrate Nutrition ....................................................................... 248 Age .......................................................................................................................................... 248 Fiber ........................................................................................................................................ 253 Ethanol .................................................................................................................................... 253
Carbohydrate Requirements ... ...... ... .... .... ...... ........ ...... ..... ... ... .. ...... ... ......... ................ .......... ... ... .. .. 256 Supplemental Readings .. .. .... ..... ...... ... .......... ..... ....... .......... ....... ....... ............. ...... ..... ........ .............. 257
Carbohydrates provide as much as 60% of the daily energy intake. The percentage of the diet that is carbohydrate varies inversely with economic conditions and with the percentage of the diet that is fat and protein. As a general rule, carbohydrate-rich foods are less expensive than fat-and proteinrich foods. Hence, as people have more disposable income, they tend to buy and consume fewer cereals, breads, fruits, and vegetables and buy more meat, butter (or margarine), milk, and eggs. This i s not always true, however. Over the last decade, education about the possible health risks of high intakes of fatty foods and the health benefits of high fiber intakes, as well as the benefits of consuming fruits and vegetables, has altered the eating habits of many consumers. This , in tum, has had an impact on the percent of intake provided by this macronutrient class.
