This document discusses carbohydrates, including their functions, food sources, classification, and digestion. Carbohydrates provide the body's primary source of energy, and come from plant foods like grains, vegetables, fruits, and milk. They are classified as monosaccharides, disaccharides, or polysaccharides. Examples like glucose, fructose, sucrose, and starch are explained. Carbohydrates have several important functions, including providing energy, sparing protein, supporting fat metabolism, and supplying fiber.

2. Objectives
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4-2
Identify the functions of carbohydrates.
Name the primary sources of
carbohydrates.
Describe the classification of
carbohydrates.

3. Facts
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4-3
Primary source of energy for the body
Least expensive and most abundant of
the energy nutrients
Named for the chemical elements they
are composed of—carbon, hydrogen, and
oxygen

4. Functions
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Provide energy
Protein-sparing action
Normal fat metabolism
Provide fiber

5. Providing Energy
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Each gram of carbohydrate provides 4
calories.
A body needs a constant energy supply.
A half day’s supply of carbohydrates is
stored in the liver and muscles for use as
needed.
Stored form is called glycogen.

6. Protein-Sparing Action
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The primary function of proteins is to build
and repair tissues.
When enough carbohydrates (at least
50–100 g/day) are ingested, proteins are
spared to be used for their primary
function.

7. Normal Fat Metabolism
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Without an adequate supply of
carbohydrates, fat is metabolized to meet
energy requirements.
Ketones are produced as a byproduct of
fat metabolism.
Ketosis may result.

8. Providing Fiber
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Dietary fiber is found in grains,
vegetables, and fruits.
Recommended intake is 20–35 g/day.
Fiber lowers blood glucose levels; may
prevent some colon cancers; and helps
prevent constipation, hemorrhoids, and
diverticular disease by softening stool.

9. Food Sources
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Principal sources
of carbohydrates
are plant foods:
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e.g. Cereal grains,
Vegetables, Fruits,
Nuts, Sugars
The only
substantial animal
source is milk.

10. Classification
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Monosaccharides
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Disaccharides
Polysaccharides
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Simple sugars
Complex carbohydrates

11. Monosaccharides
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Simplest form of carbohydrates
Absorbed directly into the bloodstream
from the small intestine
Glucose, fructose, and galactose
(continues)

12. (continued)
Monosaccharides
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Glucose
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Also called dextrose
All other forms are converted to glucose for
eventual metabolism.
Berries, grapes, sweet corn, and corn syrup
Central nervous system, red blood cells, and
brain use only glucose as fuel.
(continues)

13. (continued)
Monosaccharides
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Fructose
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Galactose
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Also called levulose or fruit sugar
Ripe fruits, honey, and soft drinks
Sweetest of all the monosaccharides
Product of the digestion of milk
Not found naturally
Source is lactose

14. Disaccharides
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Pairs of monosaccharides
Must be changed to simple sugars by
hydrolysis before absorption
Sucrose, maltose, and lactose
(continues)

15. (continued)
Disaccharides
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Sucrose
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Composed of glucose and
fructose
Form of carbohydrate
present in granulated,
powdered, and brown sugar,
and in molasses
One of the sweetest and
least expensive sugars
Sources: sugar cane, sugar
beets, maple syrup, candy,
jams, and jellies
(continues)

16. (continued)
Disaccharides
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Maltose
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Intermediary product in the hydrolysis of
starch
Also created during the fermentation process
that produces alcohol
Found in some infant formulas, malt
beverage products, and beer
Not as sweet as glucose or sucrose
(continues)

17. (continued)
Disaccharides
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Lactose
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Sugar found in milk
Distinct from other sugars in
that it is not found in plants
Helps body absorb calcium
Not as sweet as
monosaccharides or other
disaccharides

18. •
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Your client complains of bloating, abdominal
cramps, and diarrhea after drinking milk or
consuming a milk-based food such as
processed cheese.
What is the likely cause of these symptoms?
What causes this condition?
What recommendations can be made?

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Lactose intolerance is the likely cause.
Caused by insufficient lactase, the enzyme
required for the digestion of lactose.
Low-lactose milk products can be used
instead of regular milk.
Lactase-containing products are also
available.

20. Polysaccharides
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Complex carbohydrates
Compounds of many monosaccharides
Important polysaccharides in nutrition
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Starch
Glycogen
Fiber
(continues)

21. (continued)
Polysaccharides
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Starch
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Found in grains and
vegetables
Storage form of
glucose in plants
Supplies energy over
a longer period of time
because it takes the
body longer to digest
polysaccharides than
monosaccharides or
disaccharides.
(continues)

22. (continued)
Polysaccharides
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Glycogen
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Sometimes called animal starch because it is
the storage form of glucose in the body
Hormone glucagon helps liver convert
glycogen to glucose as needed
(continues)

23. (continued)
Polysaccharides
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Fiber
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It is indigestible because it
cannot be broken down by
digestive enzymes.
Insoluble: does not readily
dissolve in water (cellulose,
hemicellulose, lignins)
Soluble: partially dissolves
in water (gums, pectins,
some hemicellulose,
mucilages)

24. Sources of Polysaccharides
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Starch: cereals, grains, potatoes, corn,
beans, and yams
Glycogen: glucose stored in liver and
muscles
Cellulose: wheat bran, whole-grain
cereals, fruits, green, and leafy
vegetables
Hemicellulose: whole grains

25. Digestion and Absorption:
Monosaccharides
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Simple sugars absorbed directly into the
bloodstream
Carried to the liver; fructose and
galactose changed to glucose
Glucose then carried to cells

26. Digestion and Absorption:
Polysaccharides
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More complex; digestibility varies
Cellulose wall broken down, starch
changed to intermediate product dextrin,
then maltose, and finally glucose
Starch digestion begins in the mouth
where the enzyme salivary amylase
begins to change starch to dextrin

27. Dietary Requirements
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Food and Nutrition Board of the National
Research Council recommends:
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Half of one’s energy requirement should
come from carbohydrates, preferably
complex
Weight loss and fatigue can result from a
diet deficient in carbohydrates.
Severe deficiency can result in ketosis.
Surplus become adipose tissue.

28. Food Talk: Sugar Substitute
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A sugar substitute is a food additive that
duplicates the effect of sugar in taste, but
usually has less food energy. Some sugar
substitutes are natural and some are
synthetic. Those that are not natural are,
in general, referred to as artificial
sweeteners.

29. 
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Reasons to use Sugar
Substitute
Weight loss
Dental care
Health status
Health benefits
Cost

30. Examples of Sugar Substitutes:
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Natural
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Artificial
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Isomalt, Maltitol, Mannitol, Sorbitol, Stevia
and Xylitol
Acesulfame-K, Aspartame, Cyclamate,
Saccharin and Sucralose

31. Conclusion
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Carbohydrates provide energy.
Carbohydrates should be the major
source of energy.
These nutrients spare protein, maintain
normal fat metabolism, and provide fiber.
Excessive carbohydrate intake may lead
to obesity, dental caries, and digestive
disturbances.