The Carbohydrates:

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Chapter 4

• The Carbohydrates
• Sugars, Starches and Fibers

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Photosynthesis
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CHO in Food
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I. Carbohydrate Chemistry

• A. Carbon, Hydrogen, and Oxygen (CHO)

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CHO Structure
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CHO Structure
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II. Simple Carbohydrates

• A. Monosaccharides
• 1. Glucose
• 2. Fructose
• 3. Galactose

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Simple CHO StructureMonosaccharides
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Simple Sugars
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B. Disaccharides

• 1. Sucrose
• a. Fructose
• b. Glucose
• 2. Lactose
• a. Galactose
• b. Glucose
• 3. Maltose
• a. Glucose
• b. glucose

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Simple CHO Structure Disaccharides
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C. Chemical Reactions

• 1. condensation
• a. Joining two molecules together with water
  forming as a byproduct
• 2. hydrolysis
• a. Using water in the process of splitting a
  larger molecule into smaller parts

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Condensation Reaction
An example of a condensation reaction would be
the formation of glycogen from glucose.
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Hydrolysis Reaction
An example of a hydrolysis reaction would be the
breakdown glycogen to glucose.
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III. Complex CHO

• A. Glycogen
• 1. Storage form of glucose in animals
• a. branched molecule
• b. glucose polymer
• 2. Functions
• a. maintain blood glucose between meals
• b. Provide muscle with energy during
  anaerobic exercise

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Complex CHO
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B. Starch

• 1. Storage form of glucose in plants
• a. Amylose - Linear glucose polymer
• b. Amylopectin - Branched glucose polymer
• 2. Function
• a. Provide an energy source for the developing
  plant

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Complex CHO
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Digestibility of Complex CHO

• Start and fiber are both polymers of glucose yet
  each has a different physiological function. The
  reason for these differences lies in the bonds
  connecting the glucose molecules together. We can
  digest starch (amylopectin) and therefore derive
  energy from it however, we can not digest fiber
  and therefore derive no energy. This is because
  we have enzymes that recognize the bonds between
  the glucose molecules and catalyze their
  breakage. On the other hand our enzymes do not
  recognize the bonds between the glucose molecules
  in fiber therefore fiber is not digested. Our
  inability to digest fiber gives fiber its many
  physiological effects one of which is as a
  laxative.

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C. Dietary fibers (indigestible)

• 1. Types
• a. Cellulose - vegetables, fruits and legumes
• b. Pectins - vegetables and fruits
• c. Gums
• d. Lignin

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Fiber
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Dietary fibers (cont)

• 2. Classification of fiber
• a. Water soluble fiber
• 1. gums, pectins
• 2. found in
• a. Oat bran
• b. Barley
• c. Legumes
• d. Fruits
• 3. metabolic effects
• a. Lowers blood cholesterol
• b. Delays stomach emptying

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Classification of fiber (cont)

• b. Water insoluble fiber
• 1. cellulose, lignin
• 2. found in
• a. Vegetables
• b. Wheat
• c. Grains
• 3. metabolic effects
• a. increase laxation
• 1. Increase fecal bulk
• 2. Increase fecal water
• 3. Speed passage through intestine

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Classification of fiber (cont)

• c. Water insoluble and water soluble
• 1. metabolic effects
• a. slows starch digestion
• b. delays glucose absorption
• c. normalizes glucose tolerance

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IV. Digestion and Absorption of CHO

• A. Mouth
• 1. salivary amylase
• a. Digests starch (amylose)
• B. Stomach
• 1. HCl acid deactivates salivary amylase
• a. no starch breakdown

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Digestion and Absorption of CHO (cont)

• C. Small Intestine
• 1. Pancreatic amylase
• a. Digests amylose and dextrins
• 2. Disaccharidases
• a. Sucrase (glucose and fructose
  disaccharide)
• b. Lactase (glucose and galactose
  disaccharide)
• c. Maltase (glucose and glucose
  disaccharide)

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CHO Digestion
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CHO Digestion (cont)
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CHO Digestion (cont)
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Digestion and Absorption of CHO (cont)

• D. Large Intestine
• 1. Little starch enters large intestine
• 2. Indigestible CHO (fiber) found here
• a. Some breakdown occurs due to bacteria
  (microflora)
• b. Very little energy derived from fiber

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CHO Digestion (cont)
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Digestion and Absorption of CHO (cont)

• E. Lactose Intolerance
• 1. Lack of lactase
• 2. Hereditary or functional
• 3. Avoid use of milk products
• 4. Special foods or enzyme treatment of
  foods

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F. CHO Absorption Into Bloodstream

• 1. Small intestine primarily
• a. Active transport mostly
• 2. Absorbed into portal vein
• a. Portal vein goes directly to liver

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V. Glucose in the Body

• A. Storage and Metabolism
• 1. Storage
• a. Liver glycogen
• 1. can supply body with glucose for
  energy needs
• 2. liver stores only enough for a few
  hours
• b. Muscle glycogen
• 1. Glucose only for muscle energy

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Storage and Metabolism (cont)

• 2. Metabolism
• a. Primary energy source (especially Central
  Nervous System)
• 1. Energy (4 kcals/gram)
• b. Glycolysis
• 1. Glucose C6 to pyruvate C3
• c. Krebs cycle, citric acid cycle,
  tricarboxylic acid cycle and electron transport
  chain
• 1. C3 to CO2 and H2O

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Metabolism (cont)

• d. Gluconeogenesis
• 1. Making glucose from protein
• a. With inadequate CHO, protein is broken
  down
• b. The carbon from protein can be used to
  make glucose (gluconeogenesis)
• e. Lipogenesis
• 1. Making fat from glucose
• a. Excess calories are converted into fat
• 1. Fat is a more compact means of storing
  energy

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B. Constancy of blood glucose all cells depend
on glucose for energy metabolism to some extent
especially the central nervous system (CNS )

• 1. Glucose homeostasis
• a. Maintaining blood glucose concentration
  within a narrow critical range 70-110 mg/dl
• 1. Too low weakness, coma and death
• 2. Too high vasculature damage,
  peripheral nerve damage, wasting syndrome

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Glucose homeostasis (cont)

• b. Low blood glucose
• 1. Sensed by the pancreas, glucagon released
• 2. Glycogenolysis - break down glycogen yielding
• glucose that will increase blood glucose
• 3. Gluconeogenesis - making glucose
• c. High blood glucose
• 1. Sensed by the pancreas, insulin released
• 2. Glycogenesis

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Control of Blood Glucose
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Control of Blood Glucose
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Glucose homeostasis (cont)

• f. Glucose metabolism and time after last meal
• 1. 3-24 hours
• a. Glycogenolysis
• 2. More than 24 hours
• a. Gluconeogenesis
• 1. Protein 6 glucose
• 3. After 3-4 days of fasting (starvation)
• a. Brain adapts to using ketone bodies as
  an energy source
• b. Fatty acids 6 ketone bodies

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VI. Diabetes Mellitus (DM)

• A. Insulin Dependent DM (IDDM) 1. Pancreas
  unable to synthesize insulin 2. 5-10 of
  diabetes 3. Autoimmune disease ? B.
  Non-Insulin Dependent DM (NIDDM) 1. 90-95 of
  diabetes 2. 90 are obese 3. Pancreas
  produces insulin but cells are resistant to
  the effects

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Metabolic Consequences of Diabetes
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Diabetes Mellitus (DM) (cont)

• C. Complications of Diabetes related to ?
  blood glucose 1. Disease of the large blood
  vessels a. Poor control of blood glucose ? ?
  TG, ?HDL ? atherosclerosis b. Poor
  circulation in extremities 2. Diseases of the
  small blood vessels a. Poor circulation 1.
  Degeneration of the retina 2. Impaired kidney
  function

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Diabetes Mellitus (DM) (cont)

• 3. Diseases of the nerves a. Nerve tissue
  degeneration 1. Loss of sensation
• D. Dietary Recommendations for IDDM 1.
  Consistent pattern of food intake,
  particularly CHO a. Stabilize blood glucose
  concentration 2. Consistent activity a.
  Stabilize blood glucose concentration

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Diabetes Mellitus (DM) (cont)

• E. Dietary recommendations for NIDDM 1.
  ? weight a. Dietary modification 1. ?
  caloric input b. ? Physical activity

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VII. Health Effects and Recommended Intake of
Sugar

• A. Health Effects and Accusations Against Sugar
• 1. Nutrient deficiencies
• a. Sugar is not a nutrient dense food
• 1. sugar is empty kcals
• b. sugar can contribute to obesity
• 1. High fat
• 2. Lack of exercise

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Health Effects and Accusations Against Sugar
(cont)

• 2. Dental carries (cavities)
• a. Sugar serves as a nutrient source for
  bacteria in the mouth which produce an acid
  waste product that can dissolve tooth enamel
• b. strong positive relation
• c. sticky sweets
• d. time of eating vs. brushing
• 3. Sugar causes obesity
• a. Many times high sugar foods are also high
  fat

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Health Effects and Accusations Against Sugar
(cont)

• 4. Sugar causes heart disease
• a. most people not true
• b. small percent of people are CHO-sensitive
  1. sugar can increase blood lipids in these
  people
• 5. Sugar causes behavioral problems,
  ie. hyperactivity in children
• a. no scientific evidence
• 6. Unnatural
• a. found in most fruits and vegetables

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Health Effects and Accusations Against Sugar
(cont)

• 7. Addictive
• a. Controversial
• b. CHO cravers
• 8. Causes diabetes
• a. No scientific evidence
• b. but sugar important in control of diabetes
• 9. Causes ulcers
• a. strong relationship found in one study
• b. low refined sugar may protect against
  ulcers

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B. Recommended Intake of Sugar

• 1. No more than 10 of calories
• 2. Current US average consumption is 139
  lbs.

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VIII. Health Effects and Recommended Intake of
Starch and Fiber

• A. Health Effects of Starch and Fiber
• Positive Effects of Fiber
• 1. Weight control
• a. low in fat
• b. low in energy
• c. high in fiber
• d. high in vitamins and minerals

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Health Effects of Starch and Fiber (cont)

• 2. Heart disease
• a. High CHO diets associated with low heart
  disease
• b. Soluble fiber binds bile (cholesterol) and
  leads to a lowering of blood cholesterol
• 3. Cancer
• a. High CHO diets associated with low cancer
  incidence (especially colon)
• b. Fiber increases transit time decreasing
  exposure to potential carcinogens

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Fiber and Cholesterol

• Cholesterol is secreted into the small intestine
  in the form of bile. Much of this cholesterol is
  absorbed from the intestine and travels back to
  the liver (enterohepatic circulation) for reuse.
  Soluble fibers bind cholesterol in the small
  intestine leading to their eventual excretion.
  The enterohepatic circulation is circumvented and
  blood cholesterol levels decrease. The amount of
  the decrease is variable in individuals.

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Health Effects of Starch and Fiber (cont)

• 4. Diabetes
• a. High CHO diets associated with low
  incidence of diabetes
• b. High fiber diets help control blood glucose
• 5. GI health
• a. High fiber diets associated with lower
  incidence of hemorrhoids, diverticulitis and
  appendicitis

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Fiber and Colon Health
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Health Effects of Starch and Fiber (cont)

• Negative Effects of Fiber
• 1. Bulk may prevent sufficient intake of
  nutrients
• 2. Abdominal discomfort
• 3. Low nutrient availability
• a. Fiber can bind minerals

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B. Recommended Intake of Starch and Fiber

• 1. Starch
• a. no RDA
• b. 55-60 calories
• c. Only 10 from refined sugars

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Recommended Intake of Starch and Fiber (cont)

• 2. Fiber
• a. No RDA
• b. American Dietetic Association suggests 20
  to 35 g/day
• 1. Select from a variety of foods
• c. Table 4-4
• 1. Increase starch and fiber with
  vegetables, grains, legumes and fruits
• d. Read food labels
• e. Increase fiber slowly in diet to avoid
  discomfort

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X. Alternative Sweeteners

• A. Concept of sweetness
• 1. Taste buds
• 2. Chemical structure
• B. Relative sweetness
• 1. Sucrose 1
• 2. Fructose 1.4
• 3. Saccharin 300
• 4. Aspartame 200

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• C. Safety (National Decision)
• 1. Saccharin
• a. bladder cancer
• 2. Aspartame (aspartic acid and
  phenylalanine )
• a. phenylketonuria - PKU
• b. methanol production
• c. headaches, memory loss, dreams