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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
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.
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
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
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
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
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
Type 1 and 2 Diabetes Compared
An Obesity-Diabetes Cycle
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
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