Chapter 4: Carbohydrates: Sugars, Starches, and
Fibers
EXCI 204 — Food for Sport · Chapter Study Notes
Chapter Overview
Grains eaten 10,000 years ago were soaked, sprouted, and toasted or boiled into gruels and porridges
— dark, coarse mixtures containing all components of the grain. With grinding, smoother, purer
products were reserved for the upper classes: from the Egyptian dynasties into the 19th century, coarse
bread went to slaves and lower classes, finer bread to athletes and the upper classes. The less refined
bread was actually more nutritious (more germ and bran). The steel roller mills of the Industrial
Revolution made refined flour a staple and removed even more nutrients, eventually prompting
government mandates to add nutrients back. Today recommendations suggest moving back toward
less refined grains.
The chapter covers: (4.1) sources of carbohydrate, whole vs. refined/enriched grains, and added vs.
naturally occurring sugars; (4.2) simple and complex carbohydrates, including soluble and insoluble
fiber; (4.3) carbohydrate digestion and absorption, lactose intolerance, fiber’s effects, and glycemic
response; (4.4) carbohydrate functions — blood glucose regulation, glucose as energy, protein sparing,
and ketones; (4.5) carbohydrates in diabetes, hypoglycemia, weight management, heart disease, dental
caries, and bowel health; and (4.6) carbohydrate recommendations, choosing carbohydrates, food
labels, and nonnutritive sweeteners.
4.1 Carbohydrates in Our Food
Learning objectives: Identify sources of carbohydrate in the diet · Distinguish refined from unrefined
carbohydrates · Compare the nutrients in whole grains to those in enriched grains · Describe how foods
high in added sugars differ from foods naturally high in sugars.
High-carbohydrate foods — rice, cereal, bread, pasta, and starchy vegetables such as potatoes and
beans — are the basis of our diets: inexpensive staples making up the bulk of most meals (oatmeal for
breakfast, a sandwich for lunch, potatoes or rice and beans at dinner). Grains, vegetables, legumes,
fruits, nuts, seeds, and milk are all whole unrefined sources of carbohydrate (Figure 4.1a).
Early humans ate almost entirely whole, unrefined foods. Today we still eat unrefined carbohydrates
(quinoa, lentils, bananas, brown rice), but many foods are made with refined grains (white flour, white
rice) and some contain added sugars.
KEY DEFINITION
unrefined food — (Described in text) Foods eaten either just as they are found in nature or with only
minimal processing, such as cooking (e.g., quinoa, lentils, bananas, brown rice).
KEY DEFINITION ⭐
refined — Refers to foods that have undergone processing that changes or removes various
components of the original food.
EXCI 204 · Chapter 4 · Page 1
, KEY DEFINITION ⭐
added sugars — Refined sugars and syrups that have been added to foods during processing or
preparation.
EXAM EXAMPLE — FIGURE 4.1b
Refined vs. unrefined
Corn is a whole, unrefined carbohydrate. Cornflakes are refined — produced from corn by grinding,
cooking, extruding, and drying. The sugar you add is also refined (from sugar cane or sugar beets).
Ask Yourself: less refined → fresh peaches (vs. canned), whole-wheat bread (vs. white), oatmeal (vs.
granola cereal).
• Increased consumption of refined carbohydrates worldwide over the past few decades has been
implicated as one of the causes of the obesity epidemic and rising chronic disease.
• Recommendations: select more unrefined carbohydrates (whole grains, vegetables, fruits) and
limit foods high in refined carbohydrates (candies, cookies, sweetened beverages).
What Is a Whole Grain? ⭐
Whole grains include the entire kernel: the germ, bran, and endosperm (e.g., oatmeal, whole-wheat
toast).
KEY DEFINITION ⭐
whole grains — (Described in text) Grains that include the entire kernel of the grain: the germ, the
bran, and the endosperm.
Parts of a grain kernel ⭐
Kernel part Description (Figure 4.2a)
Endosperm Largest part; primarily starch, but also most of the kernel’s protein, plus
some vitamins and minerals
Bran Outermost layers; contain most of the fiber; good source of many vitamins
and minerals
Germ At the base; the embryo where sprouting occurs; source of oil, rich in vitamin
E
KEY DEFINITION
endosperm — (Described in text) The largest part of the kernel; made up primarily of starch, but also
contains most of the kernel’s protein, along with some vitamins and minerals.
EXCI 204 · Chapter 4 · Page 2
, KEY DEFINITION
bran — (Described in text) The outermost layers of the kernel; contain most of the fiber and are a
good source of many vitamins and minerals.
KEY DEFINITION
germ — (Described in text) The embryo at the base of the kernel, where sprouting occurs; a source
of oil and rich in vitamin E.
Sprouted grains. Grains allowed to germinate are whole grains as long as they contain the germ, bran,
and endosperm. Sprouting increases digestibility and nutrient bioavailability and may provide
additional health benefits.
KEY DEFINITION
sprouted grain — (Described in text) A grain kernel that has begun to grow into a new plant
(germinated); still contains the endosperm, bran, and germ, so it is considered a whole grain.
Refined and enriched grains. Refined grain products (e.g., white bread) include just the endosperm; the
bran and germ are discarded, losing fiber and some vitamins and minerals. To make up some losses,
refined grains sold in the U.S. must be enriched.
KEY DEFINITION ⭐
enrichment — The addition to food of specific amounts of nutrients to replace those lost during
processing.
Enrichment — what is and isn’t replaced ⭐
Nutrient In enriched refined flour vs. whole grain
Thiamin, niacin, riboflavin, iron Lost in milling, added back to levels equal to or higher
than originally present
Folic acid (folate) Added to enriched grains since 1998 (in amounts
exceeding original levels)
Vitamin E, vitamin B₆ (and others, e.g., Removed by milling and not added back
fiber, magnesium, zinc — Figure 4.2c)
Therefore foods made with enriched refined grains contain more of some nutrients and less of others
than whole-grain foods (e.g., whole-wheat bread has more vitamin B₆ but less thiamin than white
bread).
What Is Added Sugar?
• Refined sugars added during processing or at the table account for about 13% of calories in the
typical American diet.
EXCI 204 · Chapter 4 · Page 3
, • Major sources: sugar-sweetened beverages, candy, desserts and sweet snacks, and breakfast
cereals and bars; also foods we don’t think of as sweet — ketchup, salad dressings, pasta sauce.
• Refined sugars are nutritionally and chemically identical to naturally occurring sugars, but
because they are separated from their plant sources, they no longer come with vitamins,
minerals, and other substances → they contribute empty calories.
• Foods that naturally contain sugars (fruits, milk) also provide vitamins, minerals, and
phytochemicals → higher nutrient density.
• Honey, brown sugar, agave nectar, maple syrup are often seen as “natural” alternatives but are
still refined sugars, low in nutrient density, to be eaten in moderation.
EXAM EXAMPLE — FIGURE 4.3
Kiwi vs. red licorice
A kiwi (unrefined source of sugar) is more nutrient dense than licorice because it provides fiber,
vitamin C, folate, and calcium. Most licorice calories come from added sugars; four licorice strips
provide almost no vitamins or minerals and have about the same calories and carbohydrate as three
kiwis. Refined foods with added sugars are generally low in nutrient density unless nutrients were
added by fortification.
Concept Check (4.1):
1. Which foods in your diet contribute the most carbohydrate?
2. What is the difference between brown rice and white rice?
3. Why is there more vitamin B₆ and less thiamin in a slice of whole-wheat bread than in a slice of
white bread?
4. Why are foods high in added sugars low in nutrient density?
4.2 Types of Carbohydrates ⭐
Learning objectives: Name the basic unit of carbohydrate · Classify carbohydrates as simple or complex ·
Describe the types of complex carbohydrates · Distinguish soluble from insoluble fiber.
Chemically, carbohydrates are compounds made of one or more sugar units containing carbon (carbo)
plus hydrogen and oxygen in the same two-to-one proportion as water (hydrate, H₂O).
KEY DEFINITION ⭐
sugar unit — A sugar molecule that cannot be broken down to yield other sugars.
Classifying carbohydrates by sugar units ⭐
Type Number of sugar units Category
Monosaccharide One Simple
Disaccharide Two Simple
Oligosaccharide 3 to 10 (Some are fibers)
EXCI 204 · Chapter 4 · Page 4
Fibers
EXCI 204 — Food for Sport · Chapter Study Notes
Chapter Overview
Grains eaten 10,000 years ago were soaked, sprouted, and toasted or boiled into gruels and porridges
— dark, coarse mixtures containing all components of the grain. With grinding, smoother, purer
products were reserved for the upper classes: from the Egyptian dynasties into the 19th century, coarse
bread went to slaves and lower classes, finer bread to athletes and the upper classes. The less refined
bread was actually more nutritious (more germ and bran). The steel roller mills of the Industrial
Revolution made refined flour a staple and removed even more nutrients, eventually prompting
government mandates to add nutrients back. Today recommendations suggest moving back toward
less refined grains.
The chapter covers: (4.1) sources of carbohydrate, whole vs. refined/enriched grains, and added vs.
naturally occurring sugars; (4.2) simple and complex carbohydrates, including soluble and insoluble
fiber; (4.3) carbohydrate digestion and absorption, lactose intolerance, fiber’s effects, and glycemic
response; (4.4) carbohydrate functions — blood glucose regulation, glucose as energy, protein sparing,
and ketones; (4.5) carbohydrates in diabetes, hypoglycemia, weight management, heart disease, dental
caries, and bowel health; and (4.6) carbohydrate recommendations, choosing carbohydrates, food
labels, and nonnutritive sweeteners.
4.1 Carbohydrates in Our Food
Learning objectives: Identify sources of carbohydrate in the diet · Distinguish refined from unrefined
carbohydrates · Compare the nutrients in whole grains to those in enriched grains · Describe how foods
high in added sugars differ from foods naturally high in sugars.
High-carbohydrate foods — rice, cereal, bread, pasta, and starchy vegetables such as potatoes and
beans — are the basis of our diets: inexpensive staples making up the bulk of most meals (oatmeal for
breakfast, a sandwich for lunch, potatoes or rice and beans at dinner). Grains, vegetables, legumes,
fruits, nuts, seeds, and milk are all whole unrefined sources of carbohydrate (Figure 4.1a).
Early humans ate almost entirely whole, unrefined foods. Today we still eat unrefined carbohydrates
(quinoa, lentils, bananas, brown rice), but many foods are made with refined grains (white flour, white
rice) and some contain added sugars.
KEY DEFINITION
unrefined food — (Described in text) Foods eaten either just as they are found in nature or with only
minimal processing, such as cooking (e.g., quinoa, lentils, bananas, brown rice).
KEY DEFINITION ⭐
refined — Refers to foods that have undergone processing that changes or removes various
components of the original food.
EXCI 204 · Chapter 4 · Page 1
, KEY DEFINITION ⭐
added sugars — Refined sugars and syrups that have been added to foods during processing or
preparation.
EXAM EXAMPLE — FIGURE 4.1b
Refined vs. unrefined
Corn is a whole, unrefined carbohydrate. Cornflakes are refined — produced from corn by grinding,
cooking, extruding, and drying. The sugar you add is also refined (from sugar cane or sugar beets).
Ask Yourself: less refined → fresh peaches (vs. canned), whole-wheat bread (vs. white), oatmeal (vs.
granola cereal).
• Increased consumption of refined carbohydrates worldwide over the past few decades has been
implicated as one of the causes of the obesity epidemic and rising chronic disease.
• Recommendations: select more unrefined carbohydrates (whole grains, vegetables, fruits) and
limit foods high in refined carbohydrates (candies, cookies, sweetened beverages).
What Is a Whole Grain? ⭐
Whole grains include the entire kernel: the germ, bran, and endosperm (e.g., oatmeal, whole-wheat
toast).
KEY DEFINITION ⭐
whole grains — (Described in text) Grains that include the entire kernel of the grain: the germ, the
bran, and the endosperm.
Parts of a grain kernel ⭐
Kernel part Description (Figure 4.2a)
Endosperm Largest part; primarily starch, but also most of the kernel’s protein, plus
some vitamins and minerals
Bran Outermost layers; contain most of the fiber; good source of many vitamins
and minerals
Germ At the base; the embryo where sprouting occurs; source of oil, rich in vitamin
E
KEY DEFINITION
endosperm — (Described in text) The largest part of the kernel; made up primarily of starch, but also
contains most of the kernel’s protein, along with some vitamins and minerals.
EXCI 204 · Chapter 4 · Page 2
, KEY DEFINITION
bran — (Described in text) The outermost layers of the kernel; contain most of the fiber and are a
good source of many vitamins and minerals.
KEY DEFINITION
germ — (Described in text) The embryo at the base of the kernel, where sprouting occurs; a source
of oil and rich in vitamin E.
Sprouted grains. Grains allowed to germinate are whole grains as long as they contain the germ, bran,
and endosperm. Sprouting increases digestibility and nutrient bioavailability and may provide
additional health benefits.
KEY DEFINITION
sprouted grain — (Described in text) A grain kernel that has begun to grow into a new plant
(germinated); still contains the endosperm, bran, and germ, so it is considered a whole grain.
Refined and enriched grains. Refined grain products (e.g., white bread) include just the endosperm; the
bran and germ are discarded, losing fiber and some vitamins and minerals. To make up some losses,
refined grains sold in the U.S. must be enriched.
KEY DEFINITION ⭐
enrichment — The addition to food of specific amounts of nutrients to replace those lost during
processing.
Enrichment — what is and isn’t replaced ⭐
Nutrient In enriched refined flour vs. whole grain
Thiamin, niacin, riboflavin, iron Lost in milling, added back to levels equal to or higher
than originally present
Folic acid (folate) Added to enriched grains since 1998 (in amounts
exceeding original levels)
Vitamin E, vitamin B₆ (and others, e.g., Removed by milling and not added back
fiber, magnesium, zinc — Figure 4.2c)
Therefore foods made with enriched refined grains contain more of some nutrients and less of others
than whole-grain foods (e.g., whole-wheat bread has more vitamin B₆ but less thiamin than white
bread).
What Is Added Sugar?
• Refined sugars added during processing or at the table account for about 13% of calories in the
typical American diet.
EXCI 204 · Chapter 4 · Page 3
, • Major sources: sugar-sweetened beverages, candy, desserts and sweet snacks, and breakfast
cereals and bars; also foods we don’t think of as sweet — ketchup, salad dressings, pasta sauce.
• Refined sugars are nutritionally and chemically identical to naturally occurring sugars, but
because they are separated from their plant sources, they no longer come with vitamins,
minerals, and other substances → they contribute empty calories.
• Foods that naturally contain sugars (fruits, milk) also provide vitamins, minerals, and
phytochemicals → higher nutrient density.
• Honey, brown sugar, agave nectar, maple syrup are often seen as “natural” alternatives but are
still refined sugars, low in nutrient density, to be eaten in moderation.
EXAM EXAMPLE — FIGURE 4.3
Kiwi vs. red licorice
A kiwi (unrefined source of sugar) is more nutrient dense than licorice because it provides fiber,
vitamin C, folate, and calcium. Most licorice calories come from added sugars; four licorice strips
provide almost no vitamins or minerals and have about the same calories and carbohydrate as three
kiwis. Refined foods with added sugars are generally low in nutrient density unless nutrients were
added by fortification.
Concept Check (4.1):
1. Which foods in your diet contribute the most carbohydrate?
2. What is the difference between brown rice and white rice?
3. Why is there more vitamin B₆ and less thiamin in a slice of whole-wheat bread than in a slice of
white bread?
4. Why are foods high in added sugars low in nutrient density?
4.2 Types of Carbohydrates ⭐
Learning objectives: Name the basic unit of carbohydrate · Classify carbohydrates as simple or complex ·
Describe the types of complex carbohydrates · Distinguish soluble from insoluble fiber.
Chemically, carbohydrates are compounds made of one or more sugar units containing carbon (carbo)
plus hydrogen and oxygen in the same two-to-one proportion as water (hydrate, H₂O).
KEY DEFINITION ⭐
sugar unit — A sugar molecule that cannot be broken down to yield other sugars.
Classifying carbohydrates by sugar units ⭐
Type Number of sugar units Category
Monosaccharide One Simple
Disaccharide Two Simple
Oligosaccharide 3 to 10 (Some are fibers)
EXCI 204 · Chapter 4 · Page 4
