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

• 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?

• Sugar• Iron• Wood• Water• Oxygen• Alcohol

• O• I• O• I• I• O

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?

• A monosaccharide?

• A disaccharide?

• A polysaccharide?

• “sugar”

• “one sugar”

• “two sugars”

• “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

• 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)

• Saturated Fats

From Plants• Peanut Oil• Olive Oil• Corn/ Vegetable Oil

• 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 VitaminsVitamins 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 sugars and other carbon compounds.

Whole grains, legumes, many fruits 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 Plays a role in blood clotting. Produced by intestinal bacteria.

Inorganic Ions

• Sometimes called Minerals.• We only need them in small amounts.

Iron

• 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 MineralsMineral 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?

• An animal whose diet is missing one or more essential nutrients.

Giraffe eats bone to get phosphorus nutrient

Malnourishment

Aim for Fitness

1. Aim for a healthy weight

2. Be physically active each day

Build a Healthy Base3. 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 Sensibly7. 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 sugars9. Choose and prepare food with less salt

10. If you drink alcoholic beverages do so in moderation

Attack of the Killer Veggies