SUPPLEMENTAL CARBOHYDRATES POWERPOINT

The Science of Nutrition
Fifth Edition
Chapter 4
Carbohydrates: Plant-
Derived Energy Nutrients
Copyright © 2020 Pearson Education, Inc. All Rights Reserved
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What Are Carbohydrates? (1 of 4)
• One of the three macronutrients
• Important source of energy for all cells
• Preferred energy source for nerve cells
• Composed of carbon, hydrogen, and oxygen
• Good sources: fruits, vegetables, and grains

• Glucose
– The most abundant carbohydrate
– Produced by plants through photosynthesis

Figure 4.1

• Simple carbohydrates
– Referred to as sugars
– Contain one or two molecules
– Commonly referred to as sugars
• Monosaccharides contain one molecule
– Glucose, fructose, galactose, and ribose
• Disaccharides contain two molecules
– Lactose, maltose, and sucrose

Figure 4.2

Figure 4.3

• Complex carbohydrates
– Oligosaccharides contain 3 to 10 monosaccharides
– Most polysaccharides consist of hundreds to
thousands of glucose molecules
– Starch, glycogen, and most fibers

Figure 4.4

Figure 4.5

Complex Carbohydrates (1 of 6)
• Starch
– Plants store carbohydrates as starch
– Amylose—straight chain of glucose
– Amylopectin—branched chain of glucose
– Resistant starch (fiber)—glucose molecules linked
by beta bonds are largely indigestible
– Sources: grains, legumes, fruits, and vegetables

• Glycogen
– Storage form of glucose for animals (humans)
– Not found in food and therefore not a source of
dietary carbohydrate
– Stored in the liver and muscles

• Fiber
– Composed of long polysaccharide chains
– Dietary fibers are nondigestible parts of plants
– Functional fibers are nondigestible forms of
carbohydrates extracted from plants or manufactured
in a laboratory that have known health benefits
– Total fiber = Dietary fiber + Functional fiber

• Soluble fibers
– Dissolve in water; viscous and gel-forming
– Fermentable, digested by intestinal bacteria
– Regular consumption can reduce risk for
cardiovascular disease and type 2 diabetes
– Examples: pectin, gum, and mucilage
– Found in citrus fruits, berries, oats, and beans

• Insoluble fibers
– Do not dissolve in water, nonviscous
– Cannot be fermented by bacteria in the colon
– Promote regular bowel movements, alleviate
constipation, and reduce diverticulosis
– Examples: lignins, cellulose, and hemicelluloses
– Good sources: whole grains, seeds, legumes, fruits,
and vegetables

Carbohydrate Digestion (1 of 6)
• Digestion breaks down most carbohydrates into
monosaccharides
• Salivary amylase (amyl- starch, -ase an enzyme)
– Enzyme that begins starch digestion in the mouth
– Breaks starches down to maltose
• Carbohydrate digestion does not occur in the stomach
– Stomach acids inactivate salivary amylase

• Majority of carbohydrate digestion occurs in the small
intestine
• Pancreatic amylase
– Enzyme produced in the pancreas and secreted into
the small intestine
– Digests remaining starch to maltose

• Additional enzymes in the microvilli digest disaccharides
to monosaccharides
– Maltase
– Sucrase
– Lactase
• Monosaccharides are absorbed into the mucosal cells
lining the small intestine and then enter the bloodstream

• Transport
– Glucose and galactose absorbed via active transport
– Fructose absorbed via facilitated diffusion (slower
absorption)

Focus Figure 4.6

• Fructose and galactose are converted to glucose in the
liver
• Glucose in the bloodstream can provide immediate
energy
• Excess glucose is stored as glycogen in the liver and
muscles
– Liver glycogen used to maintain blood glucose and
support brain, spinal cord, and red blood cells
– Muscle glycogen provides energy to muscles during
exercise

Figure 4.7

• We do not have the enzymes necessary to digest fiber
• Bacteria in the large intestine can ferment some
undigested carbohydrates
• Fermentation produces gases and short-chain fatty acids
• Fiber remaining in the colon adds bulk to stool and is
excreted in feces

Blood Glucose Regulation
• Blood glucose regulated within a narrow range
• Hormones assist to maintain blood glucose levels:
– Insulin
– Glucagon
– Epinephrine
– Norepinephrine
– Cortisol
– Growth hormone

Blood Glucose Regulation: Insulin
• Secreted by beta cells of the pancreas
• Stimulates glucose transporters (carrier proteins) to help
move glucose from the blood across the cell membrane
• Stimulates the liver and muscle cells to take up glucose
and store it as glycogen
• Fructose does not stimulate insulin release
– Unlike glucose, fructose doesn’t stimulate satiety
signals
– Links with fructose added sugars and obesity

Focus Figure 4.8 (1 of 2)

Focus Figure 4.8 (2 of 2)

Blood Glucose Regulation: Glucagon
• Secreted by alpha cells of the pancreas
• Stimulates the liver to convert glycogen to glucose
• Assists in the breakdown of body proteins for
gluconeogenesis, the production of glucose from amino
acids

Blood Glucose Regulation: Epinephrine
and Norepinephrine
• Secreted by the adrenal glands and nerve endings when
blood glucose is low
• Increase glycogen breakdown in the liver, releasing
glucose into the blood
• Increase gluconeogenesis
• Responsible for our “fight-or-flight” reactions to danger

Blood Glucose Regulation: Cortisol and
Growth Hormone
• Secreted by the adrenal glands to act on the liver,
muscle, and adipose tissue
• Cortisol increases gluconeogenesis and decreases
glucose use by muscles and organs
• Cortisol implicated in increased risk for weight gain, CVD,
and diabetes
• Growth hormone decreases muscle glucose uptake,
increases fatty acid mobilization and use, and increases
liver glucose output

Blood Glucose Regulation: Glycemic
Index (1 of 2)
• A food’s potential to raise blood glucose
• Foods with a high glycemic index cause a sudden
surge in blood glucose, triggering a large increase in
insulin, which may be followed by a dramatic fall in blood
glucose
• Foods with a low glycemic index cause low to moderate
fluctuations in blood glucose
• Foods are assigned a glycemic index value when
compared to glycemic effect of pure glucose

Index (2 of 2)
• Not always easy to predict
• Food’s absorption rate varies with type of carbohydrate,
preparation methods, and its fat and fiber content
• Most foods are eaten in combination in a meal; glycemic
index of total meal becomes more important than the
ranking of each food

Load
• May be more useful than Glycemic Index
• Used to determine the effect of a food on a person’s
glucose response
• Grams of carbohydrates in a food are multiplied by the
glycemic index
• Glycemic index and glycemic load remain controversial

Blood Glucose Regulation: Value of
Lower Glycemic Load
• Higher fiber foods help to regulate blood glucose
• Risk reduction for heart disease and colon cancer
– Fiber helps to decrease fat levels in the blood (total
blood cholesterol and LDL)
• Foods with lower glycemic index/load:
– Legumes, fresh vegetables, and whole wheat

The Role of Carbohydrates (1 of 2)
• Energy
– Each gram of carbohydrate: 4 kilocalorie
– Red blood cells use only glucose for energy
– Brain and nervous tissue rely primarily on glucose
– Both carbohydrates and fats supply energy for daily
activities
– Glucose is especially important for energy during
exercise

Figure 4.10

The Role of Carbohydrates (2 of 2)
• Ketosis
– Occurs when carbohydrate intake is too low to supply
glucose to the brain
– Breakdown of stored fat during fasting, low
carbohydrate intake, or vigorous exercise forms
ketones
– Excess ketones increase blood acidity and cause
ketoacidosis
– Sufficient energy from carbohydrates prevents ketone
production

Carbohydrates Spare Protein
• Gluconeogenesis occurs when the diet doesn’t provide
enough carbohydrates
• The body will make its own glucose from the breakdown
of body proteins
• Amino acids from these proteins cannot be used to make
new cells, repair tissue damage, support the immune
system, or perform any other function
• Using amino acids in this way can cause serious damage
to organs (heart, liver, and kidneys)

Complex Carbohydrates Have Health
Benefits
• Fiber
– May prevent chronic and digestive diseases
– Promotes bowel health and reduces the risk of
diverticulosis and intestinal problems
– May reduce the risk of colon cancer
– May reduce the risk of heart disease
– May lower the risk of type 2 diabetes
– May enhance weight loss

Figure 4.11

Figure 4.12

How Much Carbohydrate?
• Recommended Dietary Allowance (RDA) is
130 grams/day
– Based on the amount of glucose the brain uses
– Not enough to support daily activities
• Acceptable Macronutrient Distribution Range (AMDR) is
45% to 65% of daily calories
• Focus on fiber-rich carbohydrate foods

Table 4.1 Dietary Recommendations for
Carbohydrates
Institute of Medicine (HMD)
Recommendations*
2015–2020 Dietary Guidelines for Americans†
Recommended Dietary Allowance (RDA) for
adults 19 years of age and older is 130 g of
carbohydrate per day.
The Acceptable Macronutrient Distribution Range
(AMDR) for carbohydrate is 45%–65% of total
daily energy intake.
Consume a healthful eating pattern that accounts
for all foods and beverages within an appropriate
Calorie level. A healthful eating pattern includes: a
variety of vegetables from all subgroups (dark
green, red and orange, legumes, starch and
other); fruits (especially whole fruits); grains (at
least half of which are whole grains); fat-free or
low-fat dairy; a variety of protein foods; and oils.
Added sugar intake should be 25% or less of
total energy intake each day.
Consume less than 10% of Calories per day from
added sugars.
Sources: Data from *Institute of Medicine, Food and Nutrition Board, 2005. Dietary Reference Intakes
for Energy, Carbohydrates, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids
(Macronutrients). Washington, DC: The National Academy of Sciences. Reprinted with permission.
Data from †U.S. Department of Health and Human Services and U.S. Department of Agriculture. 2015–
2020 Dietary Guidelines for Americans (8th ed.).

Simple Carbohydrates
• Diets high in simple sugars:
– Most Americans eat too much added sugar
– Contribute to tooth decay
– Increase risk factors for CVD
– Associated with diabetes and obesity

Figure 4.13

ABC News Video: Ditching Sugar

• Most Americans don’t meet the Adequate Intake (AI) for
fiber:
– 25 gram per day for women
– 38 gram per day for men, or
– 14 gram fiber per 1,000 kilocalorie consumed per day
• Whole grain foods are high in fiber, micronutrients, and
phytochemicals
• Whole grains have a lower glycemic index

Table 4.2 Terms Used to Describe Grains and
Cereals on Nutrition Labels
Term Definition
Brown bread Brown bread may or may not be made using whole-grain flour. Many brown breads are
made with white flour with brown (caramel) coloring added.
Enriched (or fortified) Enriching or fortifying involves adding nutrients to refined foods. In order to use this term in
grain products in the United States, a minimum amount of iron, folate, niacin, thiamin, and
riboflavin must be added. Other nutrients can also be added.
Refined Refining involves removing the coarse parts of food products; refined wheat flour is flour in
which all but the internal part of the kernel has been removed.
Stone ground This term refers to a milling process in which limestone is used to grind any grain. Stone
ground does not mean hat bread is made with whole grain because refined flour can be
stone ground.
Unbleached flour Unbleached flour has been refined but not bleached; it is very similar to refined white flour
in texture and nutritional value.
Wheat flour This term means any flour made from wheat; it includes white flour, unbleached flour, and
whole-wheat flour.
White flour White flour has been bleached and refined. All-purpose flour, cake flour, and enriched
baking flour are all types of white flour.
Whole-grain flour This is flour made from grain that is not refined; whole grains are milled in their complete
form with only the husk removed.
Whole-wheat flour Whole-wheat flour is an unrefined, whole-grain flour made from whole wheat kernels.

Figure 4.14

Figure 4.15

Meal Focus Maximizing Fiber Intake

Figure 4.17

Nonnutritive Sweeteners
• Limited use is not harmful within Acceptable Daily
Intake (ADI)
– Saccharin
– Acesulfame-K
– Aspartame
– Sucralose
– Neotame, Stevia, Advantame, and Monk Fruit

Table 4.3 Foods and Beverages That a Child and an
Adult Would Have to Consume Daily to Exceed the
ADI for Aspartame
Foods and Beverages 50-Pounds Child 150-Pounds
Adult
12 fluid ounces carbonated soft drink OR 5.6 17
Packets of tabletop sweetener 32 97
Source: “Sugar Substitutes: How Much Is Too Much?” from The Academy of Nutrition and
Dietetics (February 2015). Retrieved from https://www.eatright.org/food/nutrition/dietary-
guidelines-and-myplate/sugar-substitutes-how-much-is-too-much

Diabetes
• Impaired blood glucose regulation
• Type 1 diabetes
• Type 2 diabetes
• Gestational diabetes
• Uncontrolled diabetes can cause nerve damage, kidney
damage, blindness, and can be fatal
• Hyperglycemia = higher-than-normal blood glucose levels

Disorders Related to Carbohydrate
Metabolism
• Diabetes
– Type I
– Type II
• Hypoglycemia
• Lactose Intolerance

Diabetes—Type 1
• Accounts for 10% of all cases
• Most cases are diagnosed in adolescence
• Body does not produce enough insulin
• Causes hyperglycemia (high blood glucose)
• Classified as an autoimmune disease
• Requires insulin injections

Diabetes—Type 2 (1 of 5)
• Obesity can trigger cascade of changes resulting in
diabetes
• Insulin insensitivity (insulin resistance): cells become
less responsive to insulin
• Impaired fasting glucose: higher than normal blood
glucose, also called prediabetes
• Metabolic syndrome: a cluster of risk factors that
increase the risk for type 2 diabetes

Figure 4.18

• Blood tests for diabetes diagnosis
– Fasting plasma glucose (FPG)
– Oral glucose tolerance test (OGT)
– Glycosylated hemoglobin test (HbA1c, or A1c)

Focus Figure 4.20

Figure 4.22

• Nonmodifiable risk factors include age and family history
of type 2 diabetes
• Metabolic syndrome modifiable risk factors
– Abdominal obesity
– Elevated blood pressure
– Elevated blood glucose
– Unhealthy blood lipid levels

Figure 4.21

• Lifestyle choices can help prevent or control diabetes,
healthy diet and exercise lowers risk
• Dietary strategies reduce risk:
– Limit intake of added sugars
– Choose fiber-rich whole grains
– Limit consumption of red meats and processed meats
• Moderate daily exercise may be more effective than diet
alone

• Academy of Nutrition and Dietetics strategies:
– Eat meals and snacks at regular and planned times
– Eat about the same amount and types of food
– Follow Dietary Guidelines for Americans or USDA
Food Patterns
– Seek advice of a registered dietitian/nutritionist

Hypoglycemia
• Low blood glucose may cause shakiness, sweating,
anxiety, and weakness
• Reactive hypoglycemia: pancreas secretes too much
insulin after a high-carbohydrate meal
• Fasting hypoglycemia: pancreas produces too much
insulin, even when someone has not eaten

Lactose Intolerance
• Insufficient production of lactase to digest lactose-
containing foods
• Not to be confused with milk allergy
• GI symptoms: gas, cramping, and diarrhea
• Variations in extent of intolerance
• Need alternate sources of calcium

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