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Williams' Basic Nutrition & Diet
Therapy
14th Edition
Chapter 2
Carbohydrates
Copyright © 2013 Mosby, Inc., an imprint
of Elsevier Inc. All rights reserved.
1
Carbohydrates: Energy Source, Their
Structures, Role as Fiber
1. Carbohydrate foods provide practical energy sources
because of their availability, relatively low cost, and
storage capability.
2. Carbohydrate structures vary from simple to complex,
providing both quick and extended energy for the
body.
3. Dietary fiber, an indigestible carbohydrate, serves
separately as a regulatory agent within the
gastrointestinal tract.
Copyright © 2013 Mosby, Inc., an imprint
of Elsevier Inc. All rights reserved.
2
Nature of Carbohydrates (p. 13)

Relation to energy
◦ Basic fuel source
 The human body can rapidly break
down carbohydrates and they provide
the major source of energy that is
measured in calories**
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of Elsevier Inc. All rights reserved.
3
Classes of CHO’s
A CHO is composed of C, H, O
 Monosaccharides and disaccharides are
small, simple structures of only one and
two sugar units and are referred to as
simple CHO’s

Copyright © 2013, 2009, 2005 Mosby, Inc.,
an imprint of Elsevier Inc. All rights
reserved.
Classes of Carbohydrates (p. 14)

Monosaccharides
◦ Energy demands will determine if the
monosaccharides are then used for immediate
energy or stored as glycogen for later use
◦ Glucose: basic single sugar in human
metabolism
 Circulates in the blood
 AKA dextrose*
◦ Fructose: primarily found in fruits and honey*
◦ Galactose: product of lactose digestion
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5
Classes of Carbohydrates (cont’d)
(p. 15)
 Disaccharides
◦ Sucrose: common table sugar
◦ Lactose: sugar found in milk*
 *glucose and galactose
◦ Maltose: product of intermediate
breakdown of starch by the body
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6
Classes of Carbohydrates

Polysaccharides
◦ Complex carbohydrates
◦ Composed of many single-sugar units
 Starch: most significant polysaccharides
 Includes cereal, pasta, crackers, bread and
other baked goods; legumes in the form of
beans and peas, potatoes, rice, corn and
bulgur, other vegetables of the root variety*
 Glycogen: formed within body tissues; crucial to
metabolism and energy balance
 Found in liver and muscles, where it is
constantly recycled
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7
Dietary Fiber (p. 17)
Divided into two groups based on
solubility: soluble and insoluble. Cellulose,
lignin, and most hemicelluloses are not
soluble in water
 Whole grains
 Legumes
 Vegetables
 Fruits with as much skin remaining as
possible
 Table 2-2*

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8
Dietary Fiber (cont’d) (p. 17)





Health organizations emphasize role of dietary
fiber
Recommended daily intake for men age 50 and
younger: 38 g/day
For women: 25 g/day*
Increases should be gradual
The average American does not consume the
recommended servings of whole grains,
vegetables and fruit on a daily basis*
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of Elsevier Inc. All rights reserved.
9
Cellulose (p. 17)


Cellulose: chief component of cell walls in
plants
Lignin
◦ Only noncarbohydrate dietary fiber
◦ Large compound, forms woody part of some plants

Noncellulose polysaccharides
◦ Absorb water and swell to larger size, slowing
stomach emptying
◦ Bind with bile acids
◦ Provide bulk for normal muscle action
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of Elsevier Inc. All rights reserved.
10
Other Sweeteners (p. 20)
Nutritive sweeteners
◦ Sugar alcohols (sorbitol, mannitol, xylitol)
 Result in slowed digestion/osmotic
diarrhea*
 Nonnutritive sweeteners
◦ Artificial sweeteners in food
 Does not provide any kcal and present with
a sweet taste without contributing to an
individuals total energy intake*

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of Elsevier Inc. All rights reserved.
11
Functions of Carbohydrates
(p. 21)

Primary energy function
◦ Basic fuel supply
 Burn in the body at the rate of 4kcal/g*
 Physical activities
 Work of body cells
◦ Reserve fuel supply
 Liver stores about 100 g of glycogen
 Muscle stores 300-400 g
 Maintains blood glucose level
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of Elsevier Inc. All rights reserved.
12
Other Sweeteners (cont’d) (p. 22)
Copyright © 2013 Mosby, Inc., an imprint
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13
Functions of Carbohydrates (cont’d)
(p. 21)

Primary energy function (cont’d)
◦ Special tissue functions
 Liver: Glycogen reserves maintain overall energy
balance
 Carbohydrate protects protein and fat supply
 Central nervous system depends on constant
carbohydrate supply
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of Elsevier Inc. All rights reserved.
14
Food Sources of Carbohydrates (p.
22)

Starches
◦ Most important carbohydrate in the diet*
◦ Whole-grain starches such as rice, wheat,
corn, potatoes*

Sugars
◦ Not necessarily bad
◦ Added sugars provide empty calories
◦ Moderation is key
TABLE-2-5
Dairy products*
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15
Digestion of Carbohydrates
(p. 24)


Mouth
◦ Digestion of CHO foods, starches, and sugars begin in
the mouth*
◦ Mechanical or muscle functions break food mass into
smaller particles
◦ Chemical process in which enzymes begin breaking food
down
Stomach
◦ Peristalsis continues mechanical breakdown*
◦ Gastric secretions continue chemical breakdown of
nutrients
◦ Secretions do not break down carbohydrates but stop
Copyright © 2013 Mosby, Inc., an imprint
action of salivary amylase
of Elsevier Inc. All rights reserved.
16
Glycemic Index

GI ranks foods according to how fast
blood glucose levels rise after consuming
a specific amount (50g) as compared with
a reference food such as white bread or
pure glucose*
Copyright © 2013, 2009, 2005 Mosby, Inc.,
an imprint of Elsevier Inc. All rights
reserved.
Digestion of Carbohydrates (cont’d)
(p. 25)

Small intestine
◦ Peristalsis continues mechanical breakdown of
food
◦ Enzymes from pancreas and intestine continue
chemical breakdown
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18
Digestion of Carbohydrates (cont’d)
(p. 26)

Pancreatic secretions
◦ Enter duodenum through common bile duct
◦ Contain pancreatic amylase to continue
breakdown of starch

Intestinal secretions
◦ Three disaccharidases: sucrose, lactase,
maltase
◦ Render disaccharides into monosaccharides
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19
Recommendations for Dietary
Carbohydrate (p. 26)

Dietary Reference Intakes
◦ 45% to 65% of adult’s total caloric intake
should come from carbohydrate foods
◦ Limit sugar to no more than 25% of calories
consumed

Dietary Guidelines for Americans, 2010
◦ Does not provide a specific caloric number or
percentage, but does provide
recommendations
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of Elsevier Inc. All rights reserved.
20
Cultural Considerations (p26)

Lactose intolerant individuals can usually
tolerate low lactose milk products such
as cheese*
Copyright © 2013, 2009, 2005 Mosby, Inc.,
an imprint of Elsevier Inc. All rights
reserved.