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CHAPTER
2
Nutritional Needs
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Objectives
• Name the key nutrients, describe their
functions, and list important sources of each.
• Analyze the effects of various nutrient
deficiencies and excesses.
• Explain the processes of digestion,
absorption, and metabolism.
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The Nutrients
• Food provides nutrients, which are
necessary for good health
• Nutrition examines how the body uses
nutrients
• If you do not eat the foods your body needs,
you may suffer from malnutrition
continued
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The Nutrients
• Nonessential nutrients are substances the
body can make
• Essential nutrients are substances the body
cannot make and must be supplied by the
foods you eat
continued
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The Nutrients
• There are six main groups of essential
nutrients:
1.
2.
3.
4.
5.
6.
carbohydrates
fats
proteins
vitamins
minerals
water
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continued
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The Nutrients
• Failure to get enough of the needed
nutrients may result in a deficiency disease
• Consuming too much of some nutrients can
result in toxicity
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Dietary Supplements
• Doctors may recommend dietary
supplements to help make up for nutrient
shortages in the diet
• Some dietary supplements provide
nonnutrient substances, such as herbs and
some antioxidants
continued
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Dietary Supplements
• Besides supplements,
fortified foods
can be a source of
added nutrients
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Carbohydrates
• Carbohydrates are the
body’s main energy source
• They are classified as
simple or complex based
on molecular structure
• They are carried through
the bloodstream in the
form of glucose
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Functions of Carbohydrates
• Carbohydrates are sources of energy for
the body and brain
• Fiber does not provide energy, but can help
– reduce the risk of heart disease
– speed food through the body
– dilute carcinogens (cancer-causing agents)
– reduce the risk of cancer
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Sources of Carbohydrates
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• Sugars, soft drinks, and candies are sources
of simple carbohydrates
• Breads and cereals provide starches
• Fruits, vegetables, and whole grains offer fiber
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Carbohydrate Deficiencies and
Excesses
• A carbohydrate deficiency can cause the
body to use protein as an energy source
• This can interfere with the normal growth
and repair of body tissues and potentially
create a chemical imbalance
• Consuming too many simple carbohydrates
can result in nutrient shortages and excess
calories
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Fats
• Fats belong to a group of compounds called
lipids
• Lipids, which include both fats and oils,
contain fatty acids
• Based on the amount of hydrogen atoms
found in their molecules, fatty acids are
classified as saturated or unsaturated
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Types of Fats
• Saturated fatty acids have as many hydrogen
atoms as they can hold
• Unsaturated fatty acids have fewer hydrogen
atoms than they can hold
– monounsaturated
– polyunsaturated
• Hydrogenation makes unsaturated fatty acids
saturated and creates trans fatty acids
continued
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Types of Fats
• Cholesterol is a fatlike substance that
serves important functions in the body
– Part of skin tissue
– Aids in transport of fatty acids
– Produces hormones
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Think Further
Why don’t you need to add cholesterol to
your diet?
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Functions of Fats
•
•
•
•
•
•
Supply energy
Carry certain types of vitamins
Enhance flavor in foods
Tenderize meats and baked goods
Protect organs
Insulate the body
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Sources of Fats
•
•
•
•
•
•
•
•
Eggs
Dairy products
Meats
Fish
Nuts
Vegetable oils
Olives
Avocados
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Fat Deficiencies and Excesses
• A diet low in fat may result in a loss of
weight and energy
• Diets high in fat have been linked to heart
disease, some cancers, and weight gain
– No more than 35 percent of the calories in your
daily diet should come from fat
– No more than 10 percent of total calories should
come from saturated fat
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Proteins
• Proteins, the third category of essential
nutrients, are made of amino acids
– Essential amino acids
– Nonessential amino acids
• Complete proteins contain all nine essential
amino acids
• Incomplete proteins are missing one or
more of the essential amino acids
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Functions of Proteins
• Growth, maintenance, and repair of tissues
• Formation of enzymes, some hormones,
and antibodies
• Source of energy
• Regulation of bodily processes
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Sources of Proteins
•
•
•
•
•
•
•
Meat
Poultry
Fish
Dairy products
Eggs
Dried beans
Nuts
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Protein Deficiencies and
Excesses
• A protein deficiency can lead to
protein-energy malnutrition (PEM)
• Excess protein in the diet will be converted
to fat
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In Your Opinion…
What is your favorite source of protein?
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Vitamins
• Each vitamin serves unique functions
• The body cannot produce most vitamins in
quantities large enough to meet nutritional
needs
• A varied, nutritious diet is best to get the
vitamins the body needs
continued
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Vitamins
Fat-soluble vitamins Water-soluble vitamins
– vitamin A
– vitamin D
– vitamin E
– vitamin K
– vitamin C
– thiamin
– riboflavin
– niacin
– vitamin B6
– folate
– vitamin B12
– pantothenic acid
– biotin
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Fat-Soluble Vitamins
• Vitamin A
– aids the eyes with ability to see at night
– promotes bone growth
– keeps skin and other tissues healthy
– found in liver, egg yolk, and whole milk
– has higher values in orange and dark green
fruits and vegetables
continued
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Fat-Soluble Vitamins
• Vitamin D
– promotes the growth
and mineralization of
bones and teeth
– found in eggs, liver,
and fatty fish
– used to fortify most
milk, cereal, and
margarine
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continued
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Fat-Soluble Vitamins
• Vitamin E
– acts as an antioxidant
– protects red and white bloods cells, fatty acids,
and vitamin A
– common in many food items, including fats and
oils, whole-grain products, liver, eggs, whole
milk dairy foods, and leafy green vegetables
continued
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Fat-Soluble Vitamins
• Vitamin K
– aids in blood clotting
– produced in the
intestinal tract
– found in leafy green
vegetables,
cauliflower, organ
meats, and egg yolk
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Water-Soluble Vitamins
• Vitamin C (ascorbic acid)
– helps form and maintain collagen, which holds
body cells together
– firms the walls of blood vessels
– helps heal wounds and broken bones
– helps create hemoglobin and fight infections
– functions as a dietary antioxidant
– found in many fresh fruits and vegetables
continued
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Water-Soluble Vitamins
• B-complex vitamins work together in the
body
– thiamin
– riboflavin
– niacin
– vitamin B6
– folate
– vitamin B12
– biotin
continued
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Water-Soluble Vitamins
• Thiamin (B1)
– helps the body release energy from food and
promote normal appetite and digestion
– found in nearly all foods except fats, oils, and
refined sugars
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continued
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Water-Soluble Vitamins
• Riboflavin (B2)
– helps break down carbohydrates
– helps cells use oxygen
– keeps skin, tongue, and lips healthy
– found in milk, eggs, oysters, leafy green
vegetables, and whole-grain enriched cereal
products
continued
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Water-Soluble Vitamins
• Niacin
–helps keep the nervous system, mouth, skin,
tongue, and digestive tract healthy
–helps cells use nutrients
–found in meats, poultry, and peanuts
–too much niacin can cause nausea, vomiting,
and red flushing
continued
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Water-Soluble Vitamins
• Vitamin B6
– helps nerve tissues function normally
– aids with the regeneration of red blood cells
– helps break down proteins, carbohydrates,
and fats
– found in vegetables, muscle meats, and wholegrain cereals
continued
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Water-Soluble Vitamins
• Folate
– helps the body produce
normal blood cells
– folic acid is especially
important during
pregnancy
– found in green
vegetables, yogurt,
fruits, and whole-grain
cereals
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continued
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Water-Soluble Vitamins
• Vitamin B12
• Pantothenic Acid
– promotes normal
growth
– aids in normal
functioning of cells in
bone marrow, nervous
system, and intestines
– found in animal protein
foods and cereals
– helps the body use
energy nutrients and
make cholesterol
– promotes growth
– found in plant and
animal tissues, yeast,
and milk
continued
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Water-Soluble Vitamins
• Biotin
– aids in the breakdown
of fats, carbohydrates,
and proteins
– essential part of
several enzymes
– found in kidney, liver,
chicken, eggs, milk,
fresh vegetables, and
some fruits
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Vitamin Deficiencies and
Excesses
• Vitamin deficiencies can result in such
conditions and diseases as night blindness,
rickets, scurvy, beriberi, pellagra, and
anemia
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Did You Know?
The term vitamin was originally vitamine, a
combination of the words vita and amine. Vita
is Latin for life. Amine referred to amino acids,
which scientists initially thought were part of
the make up of vitamins. The final e was later
dropped when scientists learned that vitamins
did not contain amino acids.
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Minerals
• The body needs at least 21 minerals for
good health, which can be obtained from a
variety of foods
• Macrominerals are needed in large
quantities per day
• Trace elements, or microminerals, are
needed in smaller quantities per day
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Macrominerals
• Calcium
– combines with
phosphorous to build
and strengthen bones
and teeth
– helps blood clot
– keeps the heart and
nerves working properly
– found in milk, fish, and
green vegetables
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continued
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Macrominerals
• Phosphorous
– works with calcium
to build bones and
teeth
– helps the body
store and release
energy
– found in meat,
poultry, eggs, milk,
and dairy products
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continued
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Macrominerals
• Magnesium
– helps regulate the body’s temperature
– keeps the nervous system working properly
– found in whole grains and grain products, nuts,
beans, meats, and dark green leafy vegetables
continued
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Macrominerals
• Sodium, chloride, and potassium
– work as a team to control osmosis
– help the nervous system and muscles function
– help cells absorb nutrients
– common in the food supply and U.S. diet
– sources include table salt, many types of
seafood, many vegetables, and fruits
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Trace Elements
• Iron
• Zinc
– helps form
hemoglobin, which
carries oxygen
throughout the body
– found in animal
sources and leafy
green vegetables
– aids the immune
system
– promotes normal
growth and
development
– found in meats and
whole grains
continued
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Trace Elements
• Fluoride
– helps teeth develop
and resist decay
– may maintain bone
health
– found in water
• Iodine
– helps regulate
energy usage rate
– found in seafood
and iodized salt
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Mineral Deficiencies and
Excesses
• Mineral deficiencies can
cause such conditions
as osteoporosis
and goiter
• Research has shown
there is a link between
excess sodium amounts
and hypertension
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Think Further
Why do you need to vary your diet in order
to consume the essential nutrients?
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Water
• Water is the sixth
essential nutrient
• Between 50 and 75
percent of body
weight is water
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Functions of Water
• Water aids digestion, cell growth and
maintenance, chemical reactions, joint
lubrication, and temperature regulation in
the body
• Nearly all beverages and foods provide
some water
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Water Intake and Excretion
• About 80 percent of
water intake comes
from liquids
• The body excretes
most water through
the kidneys as urine
and the remaining
through the skin,
lungs, and feces
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Water Requirements
• Most people should consume about 1 ounce
of fluid for every 2 pounds of body weight
• Climate, health, and eating habits affect
water needs
• Thirst is the first symptom of water loss
• Too much water can result in water
intoxication, a rare condition
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Digestion and Absorption
• Foods must go through
the processes of
digestion and
absorption before the
body can use the
nutrients they contain
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The Digestive Tract
• The digestive or
gastrointestinal
tract is about 30
feet long
– esophagus
– stomach
– small intestine
– large intestine
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The Digestion Process
• Mechanical phase
– begins in the mouth when teeth chew food and
break it down into smaller pieces
– initiates contractions in the digestive tract,
known as peristalsis
continued
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The Digestion Process
• Chemical phase
– begins in the mouth when food mixes with
saliva
– gastric juices break down food in the stomach
– the semiliquid leaves the stomach and enters
the small intestine, where intestinal juices,
pancreatic juices, and bile act on the food
continued
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The Digestion Process
– digestive enzymes help break foods down
into simple substances the body can absorb
and use
– once digestion is complete, absorption can
take place
– some substances then travel into the large
intestine, which acts as a reservoir
– the body excretes these materials in the feces
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The Absorption Process
• Most absorption
takes place in the
small intestine
• The small intestine
is lined with millions
of villi, which aid in
absorption
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Metabolism
• Metabolism takes place in the cells after the
body absorbs nutrients
• Nutrients follow a distinct metabolic path
• Carbohydrates become glucose for energy
or glycogen for storage
continued
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Metabolism
• During fat metabolism, fats become fuel
• During protein metabolism, amino acids are
used for cell maintenance and growth or as
energy
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Review
6 points
1. What are the six essential nutrients?
1.
2.
3.
4.
5.
6.
carbohydrates
fats
proteins
vitamins
minerals
water
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Review
6 points
2. What is one function of each of the key
nutrients?
Answers will vary.
12 points
3. What are two important sources of each
of the key nutrients?
Answers will vary.
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Review
4 points
4.Describe 1 deficiency and 1 excess
disorder we learned about. Include the
name of the nutrient and describe the
disorder.
nutrient deficiencies can result in
deficiency diseases, protein-energy
malnutrition, night blindness, rickets,
scurvy, beriberi, pellagra, anemia,
osteoporosis, hypertension, and goiter;
nutrient excesses can result in toxicity
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Review
3Points
5. What occurs in the body during the
processes of digestion, absorption, and
metabolism?
digestion-breaking food down-physical
and chemical
Absorption-taking nutrients in and making
them a part of the body
Metabolism-using the food
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