Chapter4

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Chapter4

  1. 1. TheThe Carbohydrates:Carbohydrates: Sugars, Starches,Sugars, Starches, and Fibersand Fibers Chapter 4Chapter 4
  2. 2. IntroductionIntroduction • Brain • Glucose • Muscles • Glucose • Glycogen • Fat • Sources of carbohydrates • “Fattening” – mistaken thinking
  3. 3. ChemistChemist’s View of’s View of CarbohydratesCarbohydrates • Carbohydrate family • Atoms and chemical bonds • Monosaccharides • Chemical shorthand • Glucose, fructose, galactose • Disaccharides • Maltose, sucrose, lactose • Polysaccharides
  4. 4. Atoms and Their BondsAtoms and Their Bonds
  5. 5. ChemistChemist’s View of’s View of CarbohydratesCarbohydrates • Monosaccharides – three • Same numbers and kinds of atoms • Differing sweetness • Glucose – blood sugar • Part of every disaccharide • Fructose • Sweetest of the sugars • Galactose • Only in a few foods
  6. 6. Chemical Structure of Glucose
  7. 7. The Monosaccharides
  8. 8. ChemistChemist’s View of’s View of CarbohydratesCarbohydrates • Disaccharides • Pairs of three monosaccharides • Maltose – two glucose units • Sucrose – glucose and fructose • Lactose – galactose and glucose • Condensation • Links two monosaccharides together • Hydrolysis • Breaks a disaccharide in two
  9. 9. Condensation and HydrolysisCondensation and Hydrolysis of a Disaccharideof a Disaccharide
  10. 10. ChemistChemist’s View of’s View of CarbohydratesCarbohydrates • Polysaccharides • Glycogen • Storage form of energy in the body • Glucose units • Starch • Storage form of energy in plants • Glucose units
  11. 11. Glycogen and Starch Compared
  12. 12. ChemistChemist’s View of’s View of CarbohydratesCarbohydrates • Polysaccharides • Fibers • Differ from starches • Soluble fibers – benefits • Insoluble fibers – benefits • Functional fibers • Resistant starches • Phytic acid
  13. 13. The Bonds of Starch and Cellulose Compared
  14. 14. Carbohydrate DigestionCarbohydrate Digestion • Ultimate goal • Glucose for absorption and use • Hydrolysis via enzymes • Mouth • Amylase • Stomach • Stomach acid & protein-digesting enzymes • Role of fiber
  15. 15. Carbohydrate DigestionCarbohydrate Digestion • Small intestine • Most carbohydrate digestion • Pancreatic amylase • Specific disaccharide enzymes • Maltase • Sucrase • Lactase • Large intestine • Fibers
  16. 16. Carbohydrate AbsorptionCarbohydrate Absorption • Active transport • Glucose • Galactose • Facilitated diffusion • Fructose • Liver • Conversion of fructose and galactose
  17. 17. Absorption ofAbsorption of MonosaccharidesMonosaccharides
  18. 18. Lactose IntoleranceLactose Intolerance • Lactase activity • Highest immediately after birth • Declines with age • Symptoms of intolerance • Causes of intolerance beyond age • Prevalence • Genetically determined
  19. 19. Lactose IntoleranceLactose Intolerance • Dietary changes • Manage dairy consumption rather than restriction • GI bacteria • Fermented milk products • Individualized diets • Potential nutrient deficiencies • Riboflavin, vitamin D, and calcium
  20. 20. Carbohydrate MetabolismCarbohydrate Metabolism • Glucose is key player • Storing glucose as glycogen • Liver storage • Condensation into glycogen • Hydrolysis for release of glucose when needed • Muscle storage • Selfishly hoards glycogen
  21. 21. Carbohydrate MetabolismCarbohydrate Metabolism • Glucose for energy • Fuels most of body’s cells • Preferred source for brain, nerve cells, and developing red blood cells • Cellular breakdown of glucose • Making glucose from protein • Amino acid conversion • Gluconeogenesis
  22. 22. Carbohydrate MetabolismCarbohydrate Metabolism • Ketone bodies from fat fragments • Inadequate supply of carbohydrates • Fat metabolism shifts • Ketone body formation – starvation • Ketosis – acid-base balance • Carbohydrate needs for protein sparing and prevention of ketosis • Using glucose to make fat
  23. 23. The Constancy of BloodThe Constancy of Blood GlucoseGlucose • Steady supply in blood stream • Intestines – food • Liver – glycogen • Blood glucose homeostasis • Insulin • Glucose from blood into cells • Glucagon & epinephrine • Brings glucose out from storage
  24. 24. Maintaining Blood GlucoseMaintaining Blood Glucose HomeostasisHomeostasis
  25. 25. The Constancy of BloodThe Constancy of Blood GlucoseGlucose • Balancing within the normal range • Balanced meals at regular intervals • Diabetes • Insulin is either inadequate or ineffective • Type 1 diabetes • Type 2 diabetes • Hypoglycemia • Prevalence
  26. 26. The Constancy of BloodThe Constancy of Blood GlucoseGlucose • Glycemic response • Speed of glucose absorption, level of blood glucose, and return to normal glucose levels • Low glycemic response • Desired • High glycemic response • Glycemic index • Benefits • Utility
  27. 27. Health Effects of SugarsHealth Effects of Sugars • Pleasure in moderate amounts • Obesity and chronic disease • Nutrient deficiencies • Energy with few other nutrients • Discretionary kcalories • Honey • More energy per spoonful • Health benefits
  28. 28. Health Effects of SugarsHealth Effects of Sugars • Dental caries • Bacteria ferment sugars producing acid • Food factors associated with tooth decay • Time of food in mouth • Sticky foods • Frequency of sugar consumption • Food choices • Factors associated with tooth decay
  29. 29. Recommended Intakes ofRecommended Intakes of SugarsSugars • Dietary Guidelines • Reduce the intake of kcalories from added sugars • DRI • Added sugars • No more than 25% of day’s total energy • Impact on other food groups • WHO and FAO recommendations
  30. 30. Alternative SweetenersAlternative Sweeteners • Artificial sweeteners • Non-nutritive sweeteners • Large doses and adverse effects • Stevia – an herbal product • Generally recognized as safe (GRAS) • Sugar alcohols • Provide kcalories • Benefits and side effects
  31. 31. Health Effects of Starch andHealth Effects of Starch and FibersFibers • Heart disease • Whole grains • Sources • Soluble fibers • Sources • Improving heart disease risk factors • Diet composition for reducing heart disease risk
  32. 32. Health Effects of Starch andHealth Effects of Starch and FibersFibers • Diabetes • High-fiber foods • GI health • High-fiber foods • Ample fluids • Weight management • High-fiber foods and whole grains • Feeling of fullness
  33. 33. Health Effects of Starch andHealth Effects of Starch and FibersFibers • Cancer • Dietary fiber and colon cancer • Fiber supplements • Sources of dietary fiber • Phytochemicals • Preventing colon cancer • Diluting, binding, and removing • Bacterial fermentation
  34. 34. Health Effects of Starch andHealth Effects of Starch and FibersFibers • Excessive fiber • Insufficient energy or nutrient needs • Abdominal discomfort, gas, diarrhea • GI obstruction • Nutrient absorption • Dietary goals • Balance, moderation, variety
  35. 35. Characteristics, Sources, &Characteristics, Sources, & Health Effects of FibersHealth Effects of Fibers
  36. 36. Recommended Intakes ofRecommended Intakes of Starch & FibersStarch & Fibers • DRI for carbohydrates • 45 to 65% of energy requirement • RDA for carbohydrates • 130 grams per day • Fiber • DV: 11.5 grams per 1000-kcalories • DRI: 14 grams per 1000-kcalories • No UL
  37. 37. From Guidelines to GroceriesFrom Guidelines to Groceries • Grains • 1 ounce provides about 15g of carbohydrate • “Three are key” message • Vegetables • Starch content • Fruits • Milk and milk products • Protein foods
  38. 38. From Guidelines to GroceriesFrom Guidelines to Groceries • Read food labels • Total carbohydrate • Starch, fibers, sugars • Sugars • Added and natural sugars
  39. 39. Bread Labels Compared
  40. 40. Carbs, kCalories,Carbs, kCalories, andand ControversiesControversies Highlight 4Highlight 4
  41. 41. CarbohydratesCarbohydrates’ kCalorie’ kCalorie ContributionsContributions • Obesity and the link to carbohydrates • Total daily energy intakes have increased • Activity levels have declined • Increase in body weight • Epidemiological studies • Inverse relationship between carbs & weight • Weight loss • kCalorie intake
  42. 42. Energy Nutrients over Time
  43. 43. Daily Energy Intake & Increases in Adult Body Weight over Time
  44. 44. SugarsSugars’ Share in the Problem’ Share in the Problem • Increase in consumption of added sugars • High-fructose corn syrup • Body fat stores • Carbohydrate cravings • Self-imposed labeling of foods • Carbohydrate addictions • Not physiological or pharmacological
  45. 45. SugarsSugars’ Share in the Problem’ Share in the Problem • Appetite control • Fructose and insulin • Flaws in plausibility • Food form – liquid or solid • Simple to swallow • Energy regulation
  46. 46. InsulinInsulin’s Response’s Response • Surge of insulin levels • Glycemic effect • Factors impacting glycemic effect • Glycemic index and body weight • Insulin resistance • Fructose • Prediabetes and metabolic syndrome • Body’s insulin response

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