Transcript glycemic index - Cengage Learning

Chapter 4
Carbohydrates: Sugar, Starch,
Glycogen, and Fiber
Nutrition: Concepts & Controversies, 12e
Sizer/Whitney
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
feasting.
 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.
Carbohydrates
 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 Sugars
 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 –
Starch
 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 –
Glycogen
 Storage form of glucose
 Animal bodies
 Chains are longer than starch
 More highly branched
 Undetectable in meats
A Close Look at Carbohydrates Fibers
 Human digestive
enzymes cannot
break bonds
 Bacteria in large
intestine
 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
sugars
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
Foods
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,
diverticulosis
Diverticula
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
Intakes
 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 WholeGrain 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 WholeGrain 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
concentrations
 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
carbohydrate
 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
Body?
 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
Diabetes
 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
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

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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
activity
 Type 2 diabetes
vs. type 1 diabetes
Hypoglycemia
 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
Health
Controversy 4
Accusation 1: Carbohydrates Are
Making Us Fat
 Americans are
fatter
 Greater
consumption of
calories
 300-500 per day
 Epidemiological
studies
 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
disease
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
metabolism
 Fructose causes
fats to accumulate
in blood and liver
 Metabolic activities
of concern
Accusation 5: Blood Insulin Is To
Blame
 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