Carbohydrates

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Carbohydrates

  1. 1. Carbohydrates
  2. 2. Carbohydrates glucose provides energy for the brain and ½ of energy for muscles and tissues glycogen is stored glucose glucose is immediate energy glycogen is reserve energy
  3. 3. Carbohydrates all plant food milk carbohydrates are not equal – simple carbohydrates – complex carbohydrates
  4. 4. Simple Carbohydrates sugars – monosaccharides – single sugars – disaccharides – 2 monosaccharides
  5. 5. Complex Carbohydrates starches and fibers polysaccharides – chains of monosaccharides
  6. 6. Simple Carbs monosaccharides – all are 6 carbon hexes  6 carbons  12 hydrogens  6 oxygens  arrangement differs –accounts for varying sweetness – glucose, fructose, galactose
  7. 7. Glucose mild sweet flavor known as blood sugar essential energy source found in every disaccharide and polysaccharide
  8. 8. Fructose sweetest sugar found in fruits and honey added to soft drinks, cereals, deserts
  9. 9. Galactose hardly tastes sweet rarely found naturally as a single sugar
  10. 10. Disaccharides pairs of the monosaccharides – glucose is always present – 2nd of the pair could be fructose, galactose or another glucose – taken apart by hydrolysis – put together by condensation – hydrolysis and condensation occur with all energy nutrients – maltose, sucrose, lactose
  11. 11. Condensation making a disaccharide – chemical reaction linking 2 monosaccharides
  12. 12. Hydrolysis breaking a disaccharide – water molecule splits – occurs during digestion
  13. 13. Maltose 2 glucose units produced when starch breaks down not abundant
  14. 14. Sucrose fructose and glucose tastes sweet – fruit, vegetables, grains table sugar is refined sugarcane and sugar beets brown, white, powdered
  15. 15. Lactose glucose and galactose main carbohydrate in milk – known as milk sugar
  16. 16. Complex Carbohydrates polysaccharides – glycogen and starch  built entirely of glucose – fiber  variety of monosaccharides and other carbohydrate derivatives
  17. 17. Glycogen limited in meat and not found in plants – not an important dietary source of carbohydrate BUT – all glucose is stored as glycogen – long chains allow for hydrolysis and release of energy
  18. 18. Starches stored in plant cells body hydrolyzes plant starch to glucose
  19. 19. Fiber structural parts of plants – found in all plant derived food bonds of fibers cannot be broken down during the digestive process – minimal or no energy available
  20. 20. Fiber types cellulose pectins lignins resistant starches – classified as fibers – escape digestion and absorption
  21. 21. Fiber Characteristics soluble fibers, viscous, fermentable – easily digested by bacteria in colon – associated with protection against heart disease and diabetes  lower cholesterol and glucose levels – found in legumes and fruits
  22. 22. Fiber insoluble and not easily fermented – promote bowel movements – alleviate constipation – found in grains and vegetables
  23. 23. DRI and Fiber distinguish fibers by source – dietary fibers: naturally in intact plants – functional fibers: extracted from plants or manufactured – total fiber: sum of the 2
  24. 24. Carbohydrate Digestion break down into glucose – body is able to absorb and use large starch molecules – extensive breakdown disaccharides – broken once monosaccharides – don’t need to be broken down
  25. 25. Carbohydrate Digestion begins in mouth – chewing releases saliva – enzyme amylase hydrolyzes starch to polysaccharides and maltose stomach – no enzymes available to break down starch – acid does some breakdown – fibers in starch provide feeling of fullness
  26. 26.  small intestine – majority of carbohydrate digestion takes place here – pancreatic amylase reduces carbs to glucose chains or disaccharides – specific enzymes finish the job  maltase –maltose into 2 glucose  sucrase –sucrose into glucose and fructose  lactase –lactose into glucose and galactose
  27. 27.  large intestine – 1-4 hours for sugars and starches to be digested – only fibers remain  attract water, which softens stool – bacteria ferment some fibers  water, gas, short-chain fatty acids (used for energy)
  28. 28. Carbohydrate Absorption glucose can be absorbed in the mouth majority absorbed in small intestine – active transport  glucose and galactic – facilitated diffusion  fructose  smaller rise in blood glucose
  29. 29. Lactose Intolerance more lactose is consumed than can be digested – lactose molecules attract water  cause floating, abdominal discomfort, diarrhea – intestinal bacteria feed on undigested lactose  produce acid and gas
  30. 30. Lactose Intolerance age, damage, medication, diarrhea, malnutrition management requires dietary change – 6 grams (1/2 cup) usually tolerable – take in gradually – hard cheeses & cottage cheese – enzyme drops or tablets lactose free diet is extremely difficult to accomplish
  31. 31. Carbohydrate Metabolism 1/3 of body’s glycogen is stored in liver – released as glucose to bloodstream1. eat – intake glucose2. liver condenses extra glucose to glycogen3. blood glucose falls4. liver hydrolyzes glycogen to glucoseGlycogen is bulky, so we store only so much: short term energy supplyFat is the long term energy supply.
  32. 32. Glucose for Energy enzymes break apart glucose – yielding energy inadequate supply of carbohydrates – ketone bodies (fat fragments) are an alternate energy source during starvation – excess ketones can lead to ketosis: imbalance of acids in body minimum of 50 – 100 grams of carbs/day are needed to avoid ketosis
  33. 33. Glucose Homeostasis maintaining an even balance of glucose is controlled by insulin and glucagon – insulin  moves glucose into the blood – glucagon  brings glucose out of storage
  34. 34.  maintaining balance – balanced meals at regular intervals  fiber and some fat slow the digestive process down  glucose gets into the blood slow and steady
  35. 35. Intestine 1 When a person eats,Maintaining blood glucose rises. Blood Glucose Pancreas 2 High blood glucose stimulatesHomeostasis the pancreas to release insulin. Insulin 3 Insulin stimulates the uptake of glucose into cells and storage as glycogen in the liver and Liver muscles. Insulin also stimulates the conversion of excess glucose into fat for storage. Fat cell Muscle 4 As the bodys cells use glucose, blood levels decline. Pancreas 5 Low blood glucose stimulates the pancreas to release Glucagon glucagon into the bloodstream. 6 Glucagon stimulates liver cells to break down glycogen Glucose and release glucose into the blood.a Insulin Glucagon Liver Glycogen a The stress hormone epinephrine and other hormones 7 Blood glucose begins to also bring glucose out of storage. rise.
  36. 36. Imbalance diabetes – after food intake, blood glucose rises and is not regulated because insulin is inadequate hypoglycemia – blood glucose drops dramatically  too much insulin, activity, inadequate food intake, illness  diet adjustment includes fiber-rich carbs and protein
  37. 37. Glycemic Index way of classifying food according to their ability to raise blood glucose much controversy
  38. 38. Sugar ½ comes from natural sources, ½ from refined and added – sucrose, corn syrup, honey excess can lead to nutrient deficiencies and tooth decay – empty calories – sugar and starch break down in the mouth
  39. 39. Sugar recommended intake – added sugar = no more than 10% of energy intake
  40. 40. Starch and Fiber diet that includes starch, fiber and natural sugars – whole grains, vegetables, legumes, fruits  may protect against heart disease and stroke  reduces the risk of type 2 diabetes  enhances the health of the large intestine  can promote weight loss
  41. 41. Starch and Fiber  starch intake – 45-65% – 225 – 325 grams (DV is 300 grams) – 900-1300 kcal/2000 kcal – RDA is 130 grams  fiber intake – Daily Value is 25 grams/2000 kcal
  42. 42. Groceries grains: 1 serving = 15 grams vegetables – ½ cup starchy = 15 grams – ½ cup nonstarchy = 5 grams fruit: 1 serving = 15 grams milk: 1 cup = 12 grams meat: none or little legumes: ½ cup = 15 grams
  43. 43. Artificial Sweeteners help keep sugar and energy intake down anything we eat has FDA approval – saccharin – aspartame – acesulfame potassium – sucralose – neotame
  44. 44. Sugar Replacers sugar alcohols – provide bulk and sweetness  cookies, gum, candy, jelly – do contain minimal kcal – low glycemic response  absorbed slowly – do not cause dental caries

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