glycemic index

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					                Chapter 4
Carbohydrates: Sugar, Starch,
    Glycogen, and Fiber
   Nutrition: Concepts & Controversies, 12e
           Learning Objectives

 Describe the major types of carbohydrates,
  and identify their food sources.
 Describe the various roles of carbohydrates
  in the body, and explain why avoiding
  dietary carbohydrates may be ill-advised.
 Summarize how fiber differs from other
  carbohydrates and how fiber may contribute
  to health.
           Learning Objectives

 Explain how complex carbohydrates are
  broken down in the digestive tract and
  absorbed into the body.
 Describe how hormones control blood
  glucose concentrations during fasting and
 Explain the term glycemic index and how it
  may relate to diet planning.
            Learning Objectives

 Describe the scope of the U.S. diabetes
  problem and educate someone about the
  long- and short-term effects of untreated
  diabetes and prediabetes.
 Name components of a lifestyle plan to
  effectively control blood glucose and
  describe the characteristics of a diet that
  can assist in managing type 2 diabetes.
           Learning Objectives

 Compare the symptoms of postprandial
  hypoglycemia with those of fasting
  hypoglycemia, and name some diseases
  associated with the latter type.
 Discuss current research regarding the
  relationships among dietary carbohydrates,
  obesity, diabetes, and other ills.

 Ideal nutrients
   Energy needs
   Feed brain and nervous system
   Keep digestive system fit
   Keep your body lean
 Digestible and indigestible carbohydrates
 Complex vs. simple carbohydrates
      A Close Look at Carbohydrates

 Contain the sun’s radiant energy
 Green plants
   Photosynthesis
      Glucose
   Plants do not use all of the energy stored in
    their sugars
 Carbohydrate-rich foods
   Plants
   Milk
Carbohydrate – Mainly Glucose –
   Is Made by Photosynthesis
     A Close Look at Carbohydrates -
 Six sugar molecules
   Monosaccharides
      Glucose, fructose, galactose
   Disaccharides
      Lactose, maltose, and sucrose
   Digestion of mono- and disaccharides
 Chemical names end in -ose
How Monosaccharides Join to
    Form Disaccharides
     A Close Look at Carbohydrates –
 Polysaccharides
   Starch
      Plant’s storage form of glucose
   Glycogen
   Fiber
 Nutrition
   For a plant
   For a human
How Glucose Molecules Join to
   Form Polysaccharides
     A Close Look at Carbohydrates –
 Storage form of glucose
   Animal bodies
 Chains are longer than starch
   More highly branched
 Undetectable in meats
     A Close Look at Carbohydrates -
 Human digestive
  enzymes cannot
  break bonds
   Bacteria in large
      Fermentation
 Soluble vs.
  insoluble fibers
      The Need for Carbohydrates

 Critical energy source
   Nerve cells and brain
 Preferred dietary sources
   Starchy whole foods
      Complex carbohydrates
 Vital roles in the functioning body
      The Need for Carbohydrates

 Weight loss
   Caloric contribution
      Conversion into fat storage
      Refined sugars
   Increase fiber-rich whole foods
   Reduce refined white flour and added
        Why Do Nutrition Experts
      Recommend Fiber-Rich Foods?
 Health benefits
   Reduced risk of heart disease
   Reduced risk of hypertension
   Reduced risk of diabetes
   Reduced risk of bowel disease
   Promotion of healthy body weight
 Sources of fiber
Characteristics, Sources, and
  Health Effects of Fibers
Fiber Composition of Common
       Why Do Nutrition Experts
     Recommend Fiber-Rich Foods?
 Lower cholesterol and heart disease risk
   Complex carbohydrates
      More than just fiber
   Viscous fiber
      Cholesterol synthesis
 Blood glucose control
   Whole grains
     Soluble fibers
 One Way Fiber in Food May
Lower Cholesterol in the Blood
        Why Do Nutrition Experts
      Recommend Fiber-Rich Foods?
 Maintenance of digestive tract health
   All kinds of fiber
   Ample fluid intake
   Benefits of fiber
      Constipation, hemorrhoids, appendicitis,
       Why Do Nutrition Experts
     Recommend Fiber-Rich Foods?
 Digestive tract cancer and inflammation
   Ways fiber works against cancer
      Dilution
      Folate
      Resident bacteria
      Butyrate
   Recommended dietary sources
 Healthy weight management
   Appetite control
        Fiber Recommendations and
 Few people in U.S. meet recommendations
   20-35 grams of fiber daily
      Based on energy needs, age, and gender
   Adding fiber to diet
 Too much fiber?
   Dangers of excess
 Binders in fiber
   Chelating agents
   Cause of deficiencies
Usefulness of Carbohydrates
      Refined, Enriched, and Whole-
               Grain Foods
 Bread supplies much carbohydrate for
  many people
 Kernel (whole grain) has four main parts
   Germ
   Endosperm
   Bran
   Husk
A Wheat Plant and a Single
    Kernel of Wheat
      Refined, Enriched, and Whole-
               Grain Foods
 U.S. Enrichment
  Act of 1942
   Required additives
      Addition in 1996
 Advantages of
  whole grains vs.
  enriched grains
 Finding the whole
  grains in foods
 Nutrients in Whole-Grain, Enriched
White, and Unenriched White Breads
Bread Labels Compared
    From Carbohydrates to Glucose –
        Digestion & Absorption
 Starch and disaccharides are broken down
   Monosaccharides for absorption
 Starch
   Begins in the mouth
      Splits starch into maltose
   Digestion ceases in the stomach
   Digestion resumes in small intestine
      Pancreas
   Resistant starch
    From Carbohydrates to Glucose –
        Digestion & Absorption
 Sugars
   Split to yield free monosaccharides
      Enzymes on small intestine lining
   Travel to the liver
 Fiber
   Fermented by bacteria in the colon
      Odorous gas
   Gradually increase fiber intakes
 How Carbohydrate in Food
Becomes Glucose in the Body
        Why Do Some People Have
         Trouble Digesting Milk?
 Ability to digest milk carbohydrates varies
   Lactase
      Made by small intestine
 Symptoms of intolerance
   Nausea, pain, diarrhea, and gas
 Milk allergy
 Nutritional consequences
 Milk tolerance and strategies
       The Body’s Use of Glucose

 Basic carbohydrate unit used for energy
 Body handles glucose judiciously
   Maintains an internal supply
   Tightly controlling blood glucose
 Brain, nervous system, red blood cells
      Splitting Glucose for Energy

 Glucose is broken
  in half
   Can reassemble
   Broken into
    smaller molecules
      Irreversible
      Two pathways
      Splitting Glucose for Energy

 Glucose can be converted to fat
   Fat cannot be converted to glucose
   Dependence on protein when insufficient
      Protein-sparing action
 Ketosis
   Shift in body’s metabolism
      Disruption of acid-base balance
 DRI minimum of digestible carbohydrate
     How Is Glucose Regulated in the
 Two safeguard activities
   Siphoning off excess blood glucose
   Replenishing diminished glucose
 Two hormones
   Insulin
      Signals body tissues to take up glucose
   Glucagon
      Triggers breakdown of glycogen
 Epinephrine
        Handling Excess Glucose

 Body tissue shift
   Burn more glucose
      Fat is left to circulate and be stored
 Carbohydrate storage as fat
   Liver breakdown and assembly
   Costs a lot of energy
 Weight maintenance
   Dietary importance and composition
         Glycemic Index of Food

 Elevation of blood glucose and insulin
   Food score compared to standard food
 Diabetes
   Glycemic load (GL)
      Lower GL = less glucose guild up and less
       insulin needed
 Limitations of glycemic index
   Resist notion of “good” or “bad” foods
Glycemic Index of Selected Foods
 Prevalence of diabetes
   Adults
   Children
 Prediabetes
   Importance of testing
 Perils of diabetes
   Toxic effects of excess glucose
   Inflammation
   Circulation problems
Prevalence of Diabetes Among
  Adults in the United States
Warning Signs of Diabetes
              Type 1 Diabetes

 5 to 10 percent of cases
 Common age of occurrence
 Autoimmune disorder
   Own immune system attacks pancreas
   Lose ability to produce insulin
 External sources of insulin
   Fast-acting and long-acting forms
                 Type 2 Diabetes

   Predominant type of diabetes
   Lose sensitivity to insulin
   Obesity underlies many cases
   Other factors foreshadowing development
     Middle age and physical inactivity
     Body fat accumulation
     Genetic inheritance
 Prevention
Type 1 and 2 Diabetes Compared
An Obesity-Diabetes Cycle
        Management of Diabetes

 Controlling blood glucose is key
   Monitoring blood glucose levels
   Taking medications
 Control body fatness
 Establish good eating patterns
         Management of Diabetes

 Nutrition
   Goal: blood glucose levels in normal range
   Control carbohydrate intake
      Amount rather than source seems to matter
   Carbohydrate recommendations
      Varies with glucose tolerance
   Exchange system
         Management of Diabetes

 Nutrition
   Carbohydrate timing
      Evenly spaced
   Sugar alcohols
      Advantages
   Artificial sweeteners
   Weight control
         Management of Diabetes

 Physical activity
   Benefits of regular
   Type 2 diabetes
    vs. type 1 diabetes

 Rare, but true disease
   Abnormally low blood glucose
 Postprandial hypoglycemia
   Requires test to detect
 Fasting hypoglycemia
   Symptoms
 Methods to reduce symptoms
      Finding Carbohydrates in Foods

 Fruits
   Vary in water, fiber, & sugar concentrations
      Juice
 Vegetables
 Breads, grains, cereals, rice, & pasta
   Brown color does not equal whole grain
   Low-fat and low-sugar choices
      Finding Carbohydrates in Foods

 Meat, poultry, fish, dry beans, eggs, & nuts
   Nuts and legumes
 Milk, cheese, & yogurt
   High-quality protein
 Oils, solid fats, & added sugars
   Naturally occurring vs. added sugars
   Honey
     Finding Carbohydrates in Foods

 The nature of sugar
   Teaspoon values
   High-fructose corn syrup
   Concentrated juice sweeteners
   Ways to magnify sweetness without calories
Are Carbohydrates “Bad” for
        Controversy 4
     Accusation 1: Carbohydrates Are
              Making Us Fat
 Americans are
   Greater
    consumption of
      300-500 per day
 Epidemiological
 Weight loss
Percentage of Calories from Energy
    Nutrients, U.S., 1977-2006
Daily Energy Intake Over Time
       Accusation 2: Carbohydrates
            Cause Diabetes
 Obesity and diabetes
 Refined carbohydrates and diabetes
   Native Americans
 Glycemic load and diabetes
   Whole foods
        Accusation 3: Added Sugars
         Cause Obesity and Illness
 Current trends
   Daily
   Per year
 Relationship with
Added Sugars: Average U.S. Supply per
 Person Compared with USDA Prudent
         Upper Intake Limits
    Accusation 4: High-Fructose Corn
         Syrup Harms Health
 Villainy has been exaggerated
 Nature of HFCS
   Half of added sugar in U.S. food supply
 Obesity
   HCFS not a proven cause
 Liquid sugar and calorie control
 Appetite regulation
   Fructose does not stimulate insulin release
     Accusation 4: High-Fructose Corn
          Syrup Harms Health
 Effects on lipid
   Fructose causes
    fats to accumulate
    in blood and liver
   Metabolic activities
    of concern
     Accusation 5: Blood Insulin Is To
 Presence of insulin
   Body tends to store energy
 Claims made about insulin
 Expert standing on insulin
   Insulin does not cause accumulation of
    excess body fat

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