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  1. 1. Objectives    4-2 Identify the functions of carbohydrates. Name the primary sources of carbohydrates. Describe the classification of carbohydrates.
  2. 2. Facts    4-3 Primary source of energy for the body Least expensive and most abundant of the energy nutrients Named for the chemical elements they are composed of—carbon, hydrogen, and oxygen
  3. 3. Functions     4-4 Provide energy Protein-sparing action Normal fat metabolism Provide fiber
  4. 4. Providing Energy     4-5 Each gram of carbohydrate provides 4 calories. A body needs a constant energy supply. A half day’s supply of carbohydrates is stored in the liver and muscles for use as needed. Stored form is called glycogen.
  5. 5. Protein-Sparing Action   4-6 The primary function of proteins is to build and repair tissues. When enough carbohydrates (at least 50–100 g/day) are ingested, proteins are spared to be used for their primary function.
  6. 6. Normal Fat Metabolism    4-7 Without an adequate supply of carbohydrates, fat is metabolized to meet energy requirements. Ketones are produced as a byproduct of fat metabolism. Ketosis may result.
  7. 7. Providing Fiber    4-8 Dietary fiber is found in grains, vegetables, and fruits. Recommended intake is 20–35 g/day. Fiber lowers blood glucose levels; may prevent some colon cancers; and helps prevent constipation, hemorrhoids, and diverticular disease by softening stool.
  8. 8. Food Sources  Principal sources of carbohydrates are plant foods:   4-9 e.g. Cereal grains, Vegetables, Fruits, Nuts, Sugars The only substantial animal source is milk.
  9. 9. Classification  Monosaccharides    Disaccharides Polysaccharides  4-10 Simple sugars Complex carbohydrates
  10. 10. Monosaccharides    4-11 Simplest form of carbohydrates Absorbed directly into the bloodstream from the small intestine Glucose, fructose, and galactose (continues)
  11. 11. (continued) Monosaccharides  Glucose     4-12 Also called dextrose All other forms are converted to glucose for eventual metabolism. Berries, grapes, sweet corn, and corn syrup Central nervous system, red blood cells, and brain use only glucose as fuel. (continues)
  12. 12. (continued) Monosaccharides  Fructose     Galactose    4-13 Also called levulose or fruit sugar Ripe fruits, honey, and soft drinks Sweetest of all the monosaccharides Product of the digestion of milk Not found naturally Source is lactose
  13. 13. Disaccharides    4-14 Pairs of monosaccharides Must be changed to simple sugars by hydrolysis before absorption Sucrose, maltose, and lactose (continues)
  14. 14. (continued) Disaccharides  Sucrose     4-15 Composed of glucose and fructose Form of carbohydrate present in granulated, powdered, and brown sugar, and in molasses One of the sweetest and least expensive sugars Sources: sugar cane, sugar beets, maple syrup, candy, jams, and jellies (continues)
  15. 15. (continued) Disaccharides  Maltose     4-16 Intermediary product in the hydrolysis of starch Also created during the fermentation process that produces alcohol Found in some infant formulas, malt beverage products, and beer Not as sweet as glucose or sucrose (continues)
  16. 16. (continued) Disaccharides  Lactose     4-17 Sugar found in milk Distinct from other sugars in that it is not found in plants Helps body absorb calcium Not as sweet as monosaccharides or other disaccharides
  17. 17. • • • • 4-20 4-18 Your client complains of bloating, abdominal cramps, and diarrhea after drinking milk or consuming a milk-based food such as processed cheese. What is the likely cause of these symptoms? What causes this condition? What recommendations can be made?
  18. 18. • • • • 4-21 4-19 Lactose intolerance is the likely cause. Caused by insufficient lactase, the enzyme required for the digestion of lactose. Low-lactose milk products can be used instead of regular milk. Lactase-containing products are also available.
  19. 19. Polysaccharides    Complex carbohydrates Compounds of many monosaccharides Important polysaccharides in nutrition    4-20 Starch Glycogen Fiber (continues)
  20. 20. (continued) Polysaccharides  Starch    4-21 Found in grains and vegetables Storage form of glucose in plants Supplies energy over a longer period of time because it takes the body longer to digest polysaccharides than monosaccharides or disaccharides. (continues)
  21. 21. (continued) Polysaccharides  Glycogen   4-22 Sometimes called animal starch because it is the storage form of glucose in the body Hormone glucagon helps liver convert glycogen to glucose as needed (continues)
  22. 22. (continued) Polysaccharides  Fiber    4-23 It is indigestible because it cannot be broken down by digestive enzymes. Insoluble: does not readily dissolve in water (cellulose, hemicellulose, lignins) Soluble: partially dissolves in water (gums, pectins, some hemicellulose, mucilages)
  23. 23. Sources of Polysaccharides     4-24 Starch: cereals, grains, potatoes, corn, beans, and yams Glycogen: glucose stored in liver and muscles Cellulose: wheat bran, whole-grain cereals, fruits, green, and leafy vegetables Hemicellulose: whole grains
  24. 24. Digestion and Absorption: Monosaccharides    4-25 Simple sugars absorbed directly into the bloodstream Carried to the liver; fructose and galactose changed to glucose Glucose then carried to cells
  25. 25. Digestion and Absorption: Polysaccharides    4-26 More complex; digestibility varies Cellulose wall broken down, starch changed to intermediate product dextrin, then maltose, and finally glucose Starch digestion begins in the mouth where the enzyme salivary amylase begins to change starch to dextrin
  26. 26. Dietary Requirements  Food and Nutrition Board of the National Research Council recommends:     4-27 Half of one’s energy requirement should come from carbohydrates, preferably complex Weight loss and fatigue can result from a diet deficient in carbohydrates. Severe deficiency can result in ketosis. Surplus become adipose tissue.
  27. 27. Food Talk: Sugar Substitute  4-28 A sugar substitute is a food additive that duplicates the effect of sugar in taste, but usually has less food energy. Some sugar substitutes are natural and some are synthetic. Those that are not natural are, in general, referred to as artificial sweeteners.
  28. 28.      4-29 Reasons to use Sugar Substitute Weight loss Dental care Health status Health benefits Cost
  29. 29. Examples of Sugar Substitutes:  Natural   Artificial  4-30 Isomalt, Maltitol, Mannitol, Sorbitol, Stevia and Xylitol Acesulfame-K, Aspartame, Cyclamate, Saccharin and Sucralose
  30. 30. Conclusion     4-31 Carbohydrates provide energy. Carbohydrates should be the major source of energy. These nutrients spare protein, maintain normal fat metabolism, and provide fiber. Excessive carbohydrate intake may lead to obesity, dental caries, and digestive disturbances.