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The Carbohydrates Sugars Starches Fiber Carbohydrates (CH2O)n • Simple carbohydrates –Monosaccharides –Disaccharides • Complex carbohydrates Simple Carbohydrates • Monosaccharides –C6H12O6 •Glucose (dextrose, blood sugar) •Fructose •Galactose Glucose Fructose & Galactose Condensation Hydrolysis Disaccharides • Maltose = glucose + glucose • Sucrose = glucose + fructose • Lactose = glucose + galactose Complex Carbohydrates • Polysaccharides – Glycogen (animal) – Starches (plant) – Fibers (non-starch polysaccharides)-not digested well. Glycogen & Starch Molecules Compared (small Segments) Complex Carbohydrates • Fibers –Cellulose –Hemicelluloses –Pectins Complex Carbohydrates • Fibers –Gums and mucilages –Lignin –Resistant starches Complex Carbohydrates • Fibers –Soluble fibers •Viscous-Gums, pectins •Fermentable Complex Carbohydrates • Fibers –Insoluble fibers •Nonviscous-cellulose, lignins, resistant starches • (Phytic acid) Digestion • Mouth –Salivary amylase • Stomach –Fibers and satiety Digestion • Small intestine –Maltase, sucrase, lactase • Pancreas –Pancreatic amylase Carbohydrate Digestion in the GI Tract Digestion • Large intestine –Fermentation of viscous fibers •Water, gas, short-chain fatty acid production Absorption Lactose Intolerance • Symptoms-gas production, nausea, etc. • Causes –Lactase deficiency Lactose Intolerance • Prevalence-variable • Dietary changes –Does not require the elimination of milk/milk products –Acidophilus milk Glucose in the Body • Energy • Glycoproteins • Glycolipids Carbohydrate Metabolism • Storing glucose as glycogen (1/3) • Using glucose for energy Carbohydrate Metabolism • Making glucose from protein –Gluconeogenesis –Protein-sparing action of carbohydrates Carbohydrate Metabolism • Making ketone bodies from fat fragments –Ketone bodies •Ketosis –Acid-base balance Carbohydrate Metabolism • Converting glucose to fat –Energetically expensive Constancy of Blood Glucose • Regulating hormones –Insulin-uptake of sugar –Glucagon-release of sugar –Epinephrine-release (fight or flight) Maintaining Blood Glucose Homeostasis Constancy of Blood Glucose • Diabetes –Type 1 diabetes •Failure of insulin production –Type 2 diabetes-fat cells are insulin resistant! •Obesity Constancy of Blood Glucose • Hypoglycemia –Rare in healthy people Constancy of Blood Glucose • Glycemic response –Glycemic index Sugars • Added sugars –Sucrose, invert sugar, corn syrups, etc. Sugars • Health effects of sugars –Nutrient deficiencies? Sugars • Health effects of sugars –Dental caries •Dental plaque Accusations Against Sugars • Sugar causes obesity? • Sugar causes heart disease? Accusations Against Sugars • Sugar causes misbehavior in children and criminal behavior in adults? • Sugar causes cravings and addictions? –serotonin Recommended Intakes of Sugars • DRI –No more than 25% of total daily energy intake Carbs. Part II: Practical Aspects of Starches and Fibers Starch and Fiber • Health effects –Heart disease –Diabetes –GI health Starch and Fiber • Health effects –Cancer –Weight management –Harmful effects of excessive fiber intake Viscous Fibers Nonviscous Fibers Starch and Fiber • RDA for carbohydrate –130 g/day –45% - 65% total daily energy intake • Daily Value: 300 g/day Starch and Fiber • Fiber –Daily Value: 25 g/day –AI: 14 g/1000 kcal/day Guidelines to Groceries • Grains Alternatives to Sugar • Saccharine and cancer • Aspartame and PKU Artificial Sweeteners • Also called nonnutritive sweeteners – Saccharin • Used primarily in soft drinks and as a tabletop sweetener • Rapidly excreted in the urine • Does not accumulate in the body • Has been removed from list of cancer-causing substances Artificial Sweeteners • Aspartame – General purpose sweetener – Warning about phenylalanine for those with PKU – Controversial finding that aspartame may have caused cancer in rats – Excessive intake should be avoided by those with epilepsy Artificial Sweeteners • Acesulfame-K (acesulfame potassium) – Research confirms safety Artificial Sweeteners • Sucralose – Made from sugar – Passes through digestive tract • Neotame – Most recent on the market – Very sweet – Phenylalanine not an issue Artificial Sweeteners • Tagatose – Used for foods and beverages – Provides less kcalories than sugar – High doses can cause flatulence and loose stools. • Alitame and Cyclamate – Pending FDA approval – Approved in other countries Artificial Sweeteners • Acceptable Daily Intake (ADI) is the level of consumption, maintained every day and still safe by a wide margin. – Moderation and variety are still recommended. • Artificial Sweeteners and Weight Control – Much research still being done – Using artificial sweeteners will not automatically reduce energy intake. Stevia – An Herbal Alternative • Lacks research • Classified as a dietary supplement • Not required to have testing and FDA approval Sugar Replacers • Also called nutritive sweeteners, sugar alcohols, and polyols • Maltitol, mannitol, sorbitol, xylitol, isomalt, and lactitol • Absorbed more slowly and metabolized differently in the body • Low glycemic response • Side effects include GI discomfort