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Nutrition
Process by which food is taken
into the body and changed into a
form that can be utilized by cells
Nutrients
Food substances that the body
uses for normal growth,
maintenance, and repair
Bulk of organic nutrients used as
fuel to produce ATP (energy)
Energy values of foods measured
in units called kilocalories (kcal)
Nutrients (cont’d)
Most, but not all are ingested

Some synthesized in cells
Major nutrients
Make up bulk of what we eat
 Carbohydrates, proteins, lipids

Vitamins and minerals– minute
amounts
Water
Nutrients (cont’d)
Essential nutrients
Cannot be synthesized by body cells
 Must be ingested in the diet

Carbohydrates
Composed of simple sugar subunits
Primary source of energy
Monosaccharides – can be
absorbed into bloodstream

Glucose
Carbohydrates (cont’d)
Disaccharides
Polysaccharides – complex
carbohydrates
Starch
 Glycogen
 Cellulose (cannot be digested) = fiber

Carbohydrates (cont’d)
Obtained primarily from plant
products
Starches

Vegetables, seeds, grains, and nuts
Simple sugars

Fruits and candy
Glycogen

Meat
Too little = loss of weight
Too much = obesity
Carbohydrates (cont’d)
Minimum of 100 grams/day
125-175 grams/day is
recommended
Concentrate on complex
carbohydrates
55% of total calories
4 calories/gram
Proteins
Made up of amino acids

Structural building blocks of body
Body can only make 12 of 20
To obtain the other 8 (essential
amino acids) one must eat animal
sources (complete proteins)
meat
 milk
 cheese
 eggs

Proteins (cont’d)
Incomplete proteins (low in one or more
essential amino acids)




Legumes
Nuts
Seeds
Must be combined
.8 grams/ kg of body weight
4 calories/gram
Too little = weight loss & tissue wasting,
anemia & edema
Too much = obesity
Lipids
Help body absorb fat soluble
vitamins
Triglycerides - neutral fats
Most abundant form of dietary fat
 Provide reserve energy, cushion body
organs, insulates

Phospholipids

Synthesize plasma membranes and
myelin
Lipids (cont’d)
Cholesterol
Not used for stored energy
 Plasma membranes
 Structural basis of vit. D, steroid
hormones, and bile salts

Lipids (cont’d)
Saturated fats
Solid
 Animal products – meat, dairy
 Some plants - coconut

Unsaturated fats
Liquid
 Seeds, nuts, veg. oil

Lipids (cont’d)
Cholesterol

Egg yolks, meat, milk products
Linoleic and linolenic acids –
essential fatty acids
Body cannot synthesize
 Must be ingested

Lipids (cont’d)
Less than 30% of total intake
Replace sat. fats with
unsaturated
250 mg or less of cholesterol
Too little = loss of wt.; rapid
loss of heat
Too much = obesity
9 calories/gram
Vitamins
Organic compound required in small
amounts for growth and health
Coenzymes - assist enzymes in the
regulation of physiological
processes
Vitamins (cont’d)
Most are not made in the body
Must be taken in via foods or vitamin
supplements
 Exceptions
 D – made in skin
 B and K - made by intestinal bacteria
 Beta carotene – converted to A

Vitamins (cont’d)
Water-soluble
Absorbed along with water across the
intestinal wall
 B-complex vitamins & Vit. C
 Exception – B12 – must bind to intrinsic
factor to be absorbed
 Not stored in large amounts in the body
 Excreted in urine if not needed
 Damaged during food processing and
cooking

Vitamins (cont’d)
Fat-soluble
Bind to fats and are absorbed along
with the fat products of digestion
 Vit A, D, E, and K
 Except for K, stored in body
 Can have vitamin toxicity, especially
vitamin A
 Not easily damaged by cooking and
food processing

Vitamins (cont’d)
Antioxidants
A,C, & E
 Disarm tissue-damaging free radicals
and have anticancer effects

Minerals
Inorganic molecules
Make up about 4% of body by
weight (most in bones and teeth)
Most important
Ca & P
 But K, S, Na, Cl, Mg also essential

Mineral-rich foods: vegetables,
legumes, milk, some meats
Minerals (cont’d)
Incorporated into structures that
need reinforcement for strength
Work with other nutrients to ensure
a smoothly functioning body
Fine balance between uptake and
excretion important

Retain needed amounts while
preventing toxic overload
Metabolism
All chemical reactions necessary to
maintain life
Anabolism
Reactions in which larger molecules or
structures are built from smaller ones
 Energy required

Catabolism
Processes that break down complex
structures to simpler ones
 Energy released and captured to make
ATP

Carbohydrate Metabolism
As glucose is oxidized, CO2, water,
and 36 ATP are formed

Cellular respiration
Hyperglycemia – excessively high
levels of glucose in blood

Some of excess stored as glycogen or
converted to fat
Hypoglycemia – blood glucose
levels too low

Liver breaks down glycogen and
releases glucose to the blood
Lipid Metabolism
Provide reserve energy
When carbohydrates are not
available, more fats are oxidized to
produce ATP
Excessive fat breakdown causes
blood to become acidic.
Excess dietary fat stored in
subcutaneous tissue and other fat
deposits
Protein Metabolism
Amino acids most important
anabolic nutrients

Form all protein structure and the bulk
of the body’s functional molecules
Amino acids are actively taken up
from the blood by tissue cells
Once absorbed into cells, may be
used to synthesize needed proteins,
or serve as a secondary energy
source
Protein Metabolism (cont’d)
Amino acids are oxidized to form
ATP mainly when other fuel is not
available
Ammonia, released as amino acids
are catabolized, is detoxified by
liver cells that combine it with CO2
to form urea
Role of Liver in Metabolism
The body’s main metabolic organ
Plays a crucial role in processing (or
storing) virtually every nutrient
group.
Maintains homeostasis of blood
glucose levels
Degrades hormones
Detoxifies drugs and alcohol
Synthesizes plasma proteins
Role of Liver in Metabolism
(cont’d)
Forms nonessential amino acids and
converts ammonia to urea
Packages fatty acids into forms that can
be stored or transported
Stores certain vitamins
Conserves iron salvaged from worn-out
RBC
Makes cholesterol and secretes
cholesterol’s breakdown products in bile
Lipoproteins
Fats and cholesterol are transported
in the blood by lipoproteins
High-density lipoproteins (HDLs)
Transport fats from tissues throughout
the body to the liver
 Broken down to become part of bile
 Energy is used to power cellular
activities
 “Good cholesterol”
 Levels 35-60 okay; above 60 – thought
to protect against heart disease

Lipoproteins (cont’d)
Low-density lipoproteins (LDLs)
Transport cholesterol from liver to
tissues
 “Bad cholesterol”
 High levels – 160 or above

Very low-density lipoproteins
(VLDLs)

Converted to LDLs in liver
Body Energy Balance
Energy intake = total energy
output (heat + work + energy
storage)
When balanced, weight remains
stable
When not, weight is either lost or
gained
Regulation of Food Intake
Factors thought to be involved in
regulating eating behavior:
Rising and falling levels of nutrients
 Hormones
 Body temperature
 Psychological factors

Metabolic Rate
Three major food nutrients yield
different amounts of energy:
Carbohydrates and proteins: 4 kcal/g
 Fats: 9 kcal/g

Metabolic Rate (cont’d)
Basal Metabolic Rate (BMR)
Total amount of energy used by the
body when one is in a basal state (at
rest)
 Energy needed to just perform
essential life activities
 Factors influencing BMR:
 Surface area, age, gender, stress,
hormones
 Thyroxine – metabolic hormone

Metabolic Rate (cont’d)
Total Metabolic Rate (TMR)
Number of calories used by the body
to accomplish all ongoing daily
activities
 Increases greatly as muscle activity
increases
 When TMR = total calorie intake,
weight remains constant

Regulation of Body
Temperature
Body temperature - balance
between heat production and heat
loss

Normally 35.60C to 37.80C
As food is catabolized to form ATP,
more than 60% of energy released
escapes as heat, warming the body
Regulation of Body
Temperature (cont’d)
Hypothalamus initiates the
following, as necessary, to
maintain body temperature within
normal limits:
Heat-loss processes:
 Radiation of heat from skin and
evaporation of sweat or
 Heat-promoting processes:
 Vasoconstriction of skin blood
vessels and shivering

Regulation of Body
Temperature (cont’d)
Fever (controlled hyperthermia)
represents body temperature
regulated at higher than normal
levels
Weight Loss
1. Determine you resting metabolic rate
(Weight X 10)
2. Determine calories needed for activities
• Bicycling 10 mph 2.7 cal/lb/hr
• Dancing 2.6 cal/lb/hr
• Jogging 6 mph 4.2 cal/lb/hr
• Walking 3.5 mph 2.4 cal/lb/hr
• Weight training 1.9 cal/lb/hr
Weight Loss
3. Determine calories for normal
activities.
Sedentary add 20 - 40 %RMR
Moderately active add 40 - 60%RMR
Very active add 60 - 80%RMR
4. Add 1, 2, & 3 together
5. Subtract 20% of total calories
needed
Weight Gain
• Same as weight loss, but add
20%
• 60-70% Carbohydrate
• 10-15% Proteins
• Rest = Lipids