Human Nutrition
First of all…
• Why do we need to eat?
• Why do we need to eat a balanced diet?
Nutrition is:
• From Latin: “nutrire” = “nourishing”
• Obtaining organic substances and mineral ions
from which organisms obtain their energy and
raw materials for growth and tissue repair.
6 Types of Nutrients
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Carbohydrates
Proteins
Fats
Vitamins
Inorganic Ions (“Minerals”)
Water
Body Composition
Describing the Nutrients
• There are several ways to classify the classes
of nutrients.
– Organic or inorganic
– Essential or nonessential
– Macronutrient or micronutrient
– Energy yielding or not
Classifying Nutrients
• Essential nutrients – nutrients the body either
cannot make or cannot make enough of to
meet its needs.
– These nutrients must be obtained from foods
(ingested in some manner)
– Examples:
• Vitamins
• Calcium, iron, and other minerals
• Some of the amino acids
Classifying Nutrients
• Nonessential nutrients – body can make from
other nutrients ingested
 Examples:
• Cholesterol
• Some amino acids
Classifying Nutrients by
Composition
• Organic nutrients - contain carbon
• Carbohydrates
• Lipids
• Proteins
• Vitamins
• Inorganic nutrients - do not contain carbon
• Minerals
• Water
Quantity Needed
• Macronutrients: need in relatively large
amounts
– Carbohydrates, lipids, proteins
• Micronutrients: need in relatively small
amounts
– All other nutrients
Classifying Nutrients
• Energy-yielding nutrients (3):
– Carbohydrates
– Fats (lipids)
– Proteins
• Where does the energy come from?
Energy Density
Organic vs. Inorganic Nutrients
Organic
• Molecules contain Carbon
• Typically components of
plant or animal tissues.
• For example: Pepper
(ground plant fruits)
Inorganic
• No Carbon
• Typically “stand-alone”
substances.
• For example: Salt
(mineral of NaCl)
Organic or Inorganic?
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Sugar
Iron
Wood
Water
Oxygen
Alcohol
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Why Do Humans Need Nutrients?
• To give us ENERGY!
– We need energy for heat, movement, and
chemical reactions in our bodies.
– Carbs + Fats.
• To give us Building Materials:
– We need to build the cells in our bodies.
– Proteins.
Why Else?
• To give us Chemicals for Reactions
– We need chemicals to make chemical reactions
take place in our bodies.
– Proteins, vitamins, minerals, and water.
Carbohydrates
• Carbo = carbon
• Hydrate = water = hydrogen and oxygen
• So “carbs” are molecules of C, H, and O.
I bet you can do this…
• What’s a saccharide?
• “sugar”
• A monosaccharide?
• “one sugar”
• A disaccharide?
• “two sugars”
• A polysaccharide?
• “many sugars”
Simple Sugars: Monosaccharides
• A single ring of C, O,
and H.
• Glucose (yum!) 
• Fructose
• Galactose
Complex Sugars: Disaccharides
• Two sugar rings linked
together.
• Glucose +
• Galactose =
• Lactose
Complex Sugars: Polysaccharides
• 3 Types:
– Cellulose
• Makes up plant cell walls
– Starch
• Stored as food reserve in plant cells
– Glycogen
• Stored as food reserve in animal liver and muscle cells
Cellulose
Starch
Glycogen (in liver cells)
Why do we need Carbs?
• One reason: Energy!
• Plants take energy from the Sun, and turn it
into carbohydrates.
• Animals eat plants and use the energy to do
work (survive).
• Extra carbohydrates are changed into Fat.
What is a Low-Carb Diet?
• Low-carbohydrate diets restrict caloric intake
by reducing the consumption of carbohydrates
to 20 to 60 g per day (typically less than 20
percent of the daily caloric intake). The
consumption of protein and fat is increased to
compensate for part of the calories that
formerly came from carbohydrates.
• … but what are calories?
Calories
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Energy in food is measured in Calories.
Average need is 2,000 calories per day.
Carbs have lots of energy (lots of calories).
Going on a low-carb diet means you get less
energy out of your food.
• Is that a good idea?
Proteins
• A long molecule made of smaller molecules
called amino acids.
Amino Acids
• There are only 20 different amino acids.
• They can be linked in any order.
• A protein’s “identity” is based on the number
and order of amino acids.
Amino Acids
Protein Chains
Protein Molecules
Where Do We Get Proteins?
• We make them from amino acids.
• When we eat proteins, the molecules are
chopped up into amino acids.
• Then we put them back together to make the
proteins we need.
Sources of Proteins
Why Do We Need Proteins?
• Building Blocks for our cells:
– Cell membranes
– Muscle: for cells to produce movement
– Bones/Skin: Collagen
– Hair/Nails: Keratin
Keratin
Proteins are also…
• Enzymes!
(remember those?)
– Help chemical reactions take place
• Hemoglobin
– Red stuff in our blood; carries Oxygen
• Antibodies
– Attack bacteria and viruses
• Hormones – like Insulin
• Energy – but not usually
Hemoglobin
Amino Acids in Food
• Nonessential AA’s
– Our body can make them on its own.
• Essential AA’s
– Body can’t make them; they must come from
foods we eat.
– Meat, milk, and eggs contain all the essential
amino acids we need.
– Fruit, grains, and vegetables contain only some.
What about Vegetarians?
• They just have to make
sure they get all the
essential amino acids
from a diet that
includes a lot different
kinds of foods,
especially grains and
legumes (beans, etc.)
Fat
• One Fat molecule is made of:
– 1 molecule of Glycerol
– 3 fatty acids
Sources of Fat
From Animals
• Lard (pig fat)
• Fish Oil
• Butter (from milk)
From Plants
• Peanut Oil
• Olive Oil
• Corn/ Vegetable Oil
• Saturated Fats
• Unsaturated Fats
Saturated vs. Unsaturated Fats
Why Do We Need Fats?
• Energy!
– We can use it or store it.
– Fat contains more energy than carbohydrates.
– 1 gram of Fat = 2x the energy in 1 gram of Carbs
• Cell Membranes
• Heat Insulation
Fat as Insulation
Vitamins
• Organic substances that we only need in very
small amounts in our diet.
Vitamin C
Vitamin C
• Helps make the protein Collagen.
• Collagen is part of bones, skin, and blood
vessels.
• Without Vitamin C, skin and blood vessels
become weak due to lack of Collagen.
• Without enough Vitamin C, you can get a
disease called Scurvy!
– Bruises and ulcers on skin; weak gums
Scurvy
Vitamin D
Vitamin D
• Helps us absorb Calcium from food to make
bones and teeth.
• We can eat it from both plants and animals.
• We can also make it when we get enough
sunshine.
• Without enough Vitamin D, you can get a
disease called Rickets!
– Bone is soft and grows into bent shapes
Rickets
Vitamin A
• Helps with a LOT of functions in the body.
• Without enough Vitamin A, impaired vision or
blindness can occur.
Vitamin A
Major Vitamins
Vitamins
Major roles
Natural sources
Vitamin A (fat soluble
Used to make visual pigments; maintains
epithelial tissues; needed for normal
growth.
Orange and yellow fruits and
vegetables, egg yolk, dairy products.
B complex vitamins
(water soluble)
Used in cellular respiration to metabolize Whole grains, legumes, many fruits
sugars and other carbon compounds.
and vegetables. B12 comes from
animal sources.
Vitamin C (water
soluble)
Used in collagen synthesis, possible role
in immune function.
Fresh fruits and vegetables.
Vitamin D (fat
soluble)
Bone growth, calcium absorption,
possible role in immune function.
Eggs, dairy products. Sunlight on skin
oils creates Vitamin D.
Vitamin E (fat soluble) Antioxidant, reduces cellular damage.
Nuts, whole grains, leafy vegetables.
Vitamin K
Produced by intestinal bacteria.
Plays a role in blood clotting.
Inorganic Ions
• Sometimes called Minerals.
• We only need them in small amounts.
Iron
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Helps us make Hemoglobin.
Makes our blood red!
Carries Oxygen in our blood.
Without enough Iron, you can get a disease
called Anemia!
– Feel tired very easily
Iron in Blood
Calcium
• Our bones and teeth are made of calcium
salts.
• Without enough calcium…?
• Need Vitamin D to absorb it.
Calcium
Sources of Calcium
Major Minerals
Mineral
Major roles
Natural sources
Calcium
Bone and tooth formation; muscle and
nerve function.
Dairy products, leafy greens, dry beans.
Iron
Used to make hemoglobin and
myoglobin.
Red meats, eggs, nuts, whole grains,
leafy greens.
Zinc
Component of certain enzymes, required
for growth.
Meats, whole grains, nuts, legumes.
Phosphorous
Bone and tooth formation; pH of body
fluids, phospholipids.
Dairy products, grains.
Potassium
Maintains pH of body fluids; used in
action potentials.
Many fruits and vegetables, meats, milk.
Sodium
Maintains pH of body fluids; used in
action potentials.
Table salt, meats.
Selenium
Used by the immune system.
Nuts, esp. Brazil nuts; many fruits and
vegetables.
Water
• Inorganic
• No energy-yielding
• But EXTREMELY essential
Antioxidants
• Free-radicals are
released by cell
damage and many
cell processes.
• Anti-oxidants, such as
Vitamins C and E, and
many plant pigments,
combine with free
radicals and reduce
their effects, which
slows cell aging.
Moral of the story: eat colorful
food
No, Skittles don’t count as
“colorful food!”
Food Guide Pyramid
So… Why do we need a Balanced
Diet?
Malnourishment
• An animal whose diet is missing one or
more essential nutrients.
Giraffe eats bone to get phosphorus
nutrient
Aim for Fitness
1. Aim for a healthy
weight
2. Be physically active each day
Build a Healthy Base
3. Let the pyramid guide your choices
4. Choose a variety of grains daily, especially
whole grains
5. Choose a variety of fruits and vegetables
daily.
6. Keep food safe to eat.
Choose Sensibly
7. Choose a diet that is low in saturated fat and cholesterol
and moderate in total fat
8. Choose beverages and foods to moderate
your intake of sugars
9. Choose and prepare food with less salt
10. If you drink alcoholic beverages do so in
moderation
Attack of the Killer Veggies