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The Liver

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					Chapter 4:
Carbohydrates
Plants Synthesize
     Glucose
    Monosaccharides
Structure
Glucose
Fructose
Galactose
 Fructose (fruit sugar)
Metabolized to glucose in the liver
Found in fruit, honey, and high fructose
corn syrup
Is in sucrose
          Galactose
Usually bound with glucose (lactose)
Converted to glucose in the liver
Available fuel source
         Disaccharides
“Simple sugars”
Maltose (Gluc + Gluc)
 Fermentation
 Alcohol production

Sucrose (Gluc + Fruc)
   Sugar
Lactose (Galactose + Gluc)
   Milk products
Complex Carbohydrates
Polysaccharides: Starch & Glycogen
Amylose
Amylopectin
Dietary fiber
    Oligosaccharides
3-10 monosaccharides
Found in beans and legumes
Not digested
Metabolized by bacteria in the large
intestine
Beno®
    Polysaccharides:
         Starch
3,000 or more monosaccharides bound
together
Starch
 Amylose--straight chain polymer
 Amylopectin--highly branched polymer
           Glycogen




Storage form of CHO for animals and human
Structure similar to amylopectin
More sites for enzyme action
Found in the liver and muscles
         Dietary Fiber

Undigested plant food
Body cannot break the bonds
Insoluble fiber
 Cellulos, hemicellulose, lignin
 Not fermented by the bacteria in the colon

Soluble fiber
 Gum, Pectin, Mucilage
 Fruit, vegetable, rice bran, psyllium seed
Soluble and Insoluble
        Fiber
   Health Benefits of
     Dietary Fiber
Absorbs and holds water
Soften stool
Larger stool promotes peristalsis
Promotes regularity
Lower risk for cardiovascular disease
Decrease hemorrhoids and diverticula
Diverticula
CHO in Food
        Sweeteners
Sucrose--benchmark of all sweeteners
Same caloric content (4 kcals/gm)
No health benefit over another
Consumption ranges: 14-48 lbs/yr per
person
Types of Sweeteners
High-fructose corn syrup
   cornstarch treated with acid and enzymes
   conversion of glucose into fructose
   same degree of sweetness as sucrose
   cheaper and used in many food products
Brown sugar
Maple syrup
Honey
Sugar alcohols
   1.5-3 kcal/g
   Absorbed and metabolized slower
   Large amount causes diarrhea
     Sugar Substitutes
Saccharin
 First produced in 1879
 180-200x sweeter than sucrose
 Excessive intake is linked to bladder
 cancer in lab animals
 Not a potential risk in humans
Aspartame (NutraSweet)
 Composed of phenylalanine, aspartic acid,
 and methanol
 180-200x sweeter than sucrose
 4 kcal/gm, but only a trace amount is needed
 to sweeten foods
 Not heat stable
 Complaints of sensitivity to aspartame
    headaches, dizziness, seizures, nausea, etc.
 Not recommended for people with
 phenylketonuria (PKU)
Acesulfame-K (Sunette)

Newest sugar substitute
200x sweeter than sucrose
Not digested by the body
Heat stable
Diabetisweet used in baking
Sucralose (Splenda)
600x sweeter than sucrose
Substitute chlorines for hydroxyl
groups on sucrose
Heat stable
Tiny amount digested
Digestion
   Effects of Cooking
Softens fibrous tissues
Easier to chew and swallow
     Digestion of
  Carbohydrate in the
        Mouth
Saliva contains amylase
Starch is broken down to shorter
saccharides
Taste the sweetness with prolong
chewing
Proceeds down the esophagus
     Digestion of
  Carbohydrate in the
       Stomach

The acidic environment stops the
action of salivary amylase
No further starch digestion occurs
 In the Small Intestine
Pancreatic amylase is released
Intestinal cells release enzymes
Maltose + maltase   glucose + glucose
Sucrose + sucrase    glucose + fructose
Lactose + lactase   glucose + galactose
Monosaccharides are absorbed
CHO Digestion
       CHO Absorption
Glucose and Galactose
  Active absorption
  Energy is expended
  Going from low to high concentration gradient
Fructose
  Facilitated diffusion using a carrier
  No energy expended
           Portal Vein
  Transport absorbed monosaccarhides
  Delivers them to the liver
Liver can:
  transform them into glucose
  release them back into the blood stream
  store as gylcogen (or fat)
      Functions of
      Carbohydrate

Supplies energy
Protein sparing
Prevent ketosis
Sweetener
 Regulation of Blood
      Glucose

Hyperglycemia
Hypoglycemia
Blood Glucose Control
Role of the liver
 Regulates glucose that enters
  bloodstream
Role of the pancreas
 Release of insulin

 Release of glucagon
  Functions of Insulin
Promotes glycogen synthesis
Increases glucose uptake by the
cells
Reduces gluconeogenesis
Net effect: lowers the blood
glucose
Functions of Glucagon
Breakdown glycogen
Enhances gluconeogenesis
Net effect: raises blood glucose
        Epinephrine/
       Norepinephrine
“fight or flight” response
breakdown glycogen
raises blood glucose
Diabetes Mellitus-Type 1
 Genetic link
 Decreased release of insulin
 Insulin dependent
 Hyperglycemia
 Immunological disorder
 Early introduction of cow’s milk
 Treatment for Type 1
CHO counting
Insulin therapy
Risk for heart disease
Diabetes Mellitus-Type 2
 Genetic link
 Associated with obesity
 Non-insulin dependent to start
 Accounts for majority of cases of DM
 Defective insulin receptors on the cells
 Over secretion of insulin to compensate
 Leads to beta cells failure
 Treatment: medication and diet therapy
 (weight loss)
     Consequences of
    Uncontrolled Blood
         Glucose
Ketosis leading to ion imbalances,
dehydration, coma, death
Degenerative diseases
   Nerve damage, Heart disease, Kidney
    disease, Blindness
Atherosclerosis
Increase risk for wound infections
      Hypoglycemia
Reactive hypoglycemia
 Occurs 2-4 hours after eating a meal

 Possibly due to over secretion of
  insulin
Fasting hypoglycemia
 Usually caused by pancreatic cancer

 Leads to overproduction of insulin
 Sweetener Function
Enhances flavor
Use in moderation
Recommended Intake
No RDA (yet)
Consume at least 50 gm to prevent
ketosis
National Cholesterol Education Program
recommends 50-60% of kcal from CHO
Current intake is ~50%
  Health Benefits of
 Dietary Fiber--Recall
Promotes softer, larger stool and
regularity
Slows glucose absorption
Reduces blood cholesterol
Reduces heart disease
Reduces hemorrhoids and diverticula
Recommended Dietary
    Fiber Intake
20-35 gm of fiber/day (10-13 gm/1000 kcals)
Children: age +5gm/day
Ave. U.S. intake: ~16 gm/day
Too much fiber (>60 gm/d) will:
   require extra intake of fluid
   bind to some minerals
   develop phytobezoars
   fills the stomach of a young child quickly
 Recommendation for
 Simple Sugar Intake
Low nutrient density
Recommends no more than 10% of
total kcal/day
Ave. U.S. intake: 16% of total kcal/day
Added to food and beverages
during processing
       High Sugar Diets
Empty calories
Soda replacing milk
Calories adding to excess
Dental caries
   exposure to teeth
High glycemic index
 Blood glucose response of a given food
 Influence by various factors
Effects of High Glycemic
       Index CHO
 Stimulates the release of insulin
 Insulin’s effect blood triglycerides level
 Insulin’s effect LDL
 Insulin increases fat synthesis
 Return to hunger quicker
 Develop insulin resistance
    Lactose Intolerance
Reduction in lactase
 Lactose is undigested and not absorbed
 Lactose is metabolized by large intestinal
  bacteria
       causes gas, bloating, cramping, discomfort
Primary lactose intolerance disease
Secondary lactose intolerance disease
What To Do If You Are
 Lactose Intolerance
Determine amount you can tolerate
Eat dairy with fat
Cheese & yogurt are usually tolerated
well
Use of Lact-Aide

				
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posted:7/13/2011
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