Human Nutrition

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Human Nutrition
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Digestive System
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NutrientsUtilized or Stored Until Needed
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Food Guide Pyramid
Diet and regular exercise
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Nutrition - Macronutrients

• Carbohydrates major energy source, simple or
  complex. Metabolic rate related to glycemic
  index
• Lipids cell components and energy sources,
  saturated or unsaturated, transfats, omega oils
• Proteins 20 natural amino acids, building and
  repair, hormones, enzymes
• Water solvent, thermoregulation, metabolic
  processes

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Nutrition - Micronutrients

• Vitamins fat soluble and water soluble
• Minerals recommended daily allowance (rda)
• Fiber undigested complex carbs, some evidence
  decreases colon cancer

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Carbohydrates

• General formula ratio is for most carbohydrates
  is CH2O
• Carbohydrate rich foods in their natural state
  are low in calories and high in fiber (AKA as
  cellulose, plant fibers we do not digest).
• Carbohydrates contain about 4 calories per gram
  (fats about 9 cal per gram).

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Simple Carbohydrates

• Also called simple sugars.
• Simple carbohydrates include monosaccharides and
  disaccharides such as
• fructose (fruit sugar),
• sucrose (table sugar) and
• lactose (milk sugar), as well as several other
  sugars.
• Simple carbohydrates are sources of quick energy.

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Complex Carbohydrates

• Complex carbohydrates include fiber and starches.
  
• Found in vegetables, bread, rice, oatmeal, whole
  grains, peas and beans.
• Meats also provide carbs in the form of
  glycogens.

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Complex Carbohydrates

• Complex carbohydrates take longer to be digested,
  so your body needs more time to release these
  carbs into your blood as glucose.
• This results in sustained energy (stamina).
• Glycemic Index refers to how quickly foods are
  metabolized. (more about this later)

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Undigestible Complex Carbohydrates

• Also called fiber
• Essential role in large
  intestine health
• Brushes walls of
  large intestine

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Carbohydrates and Blood Sugar

• Carb rich foodsgt Blood Glucose levels
  dramatically
• Pancreas secretes insulin so that glucose units
  can be taken into body cells for use during
  cellular respiration (producing ATP)

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Carbohydrates and Blood Sugar

• Diabetes

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Blood Sugar

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Glucose to Glycogen
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Glycemic Index

• High glycemic foods are used quickly and stored
  as fat tissue easily.
• Low glycemic foods provided more long term energy
  and reduced insulin levels (which is a good
  thing).

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Glycemic Index

•  

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Glycemic Index

• High glycemic index food consumption results in
  more and more insulin required to have the same
  effect on the tissues
• This phenomenon is known as insulin resistance,
  and is the first step towards diabetes.

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Glycemic Index
Highglycemic index Mediumglycemic index Lowglycemic index
Maltose (beer) Rye bread (crispbread) Oatmeal porridge
Cooked parsnips Muesli (no sugar) Wholewheat pasta
Cooked carrots Brown rice Sweet potato
White Rice Cooked beets Dried Peas
Biscuits / cookies Garden peas Apples
Baked potato Boiled potato Pears
Cornflakes / cereal Wholewheat bread Whole milk
Bagels Corn, polenta Kidney beans
White Bread Sultanas / raisins Lentils
Corn chips Orange juice Soybeans
Mangoes Oatmeal biscuits / cookies High water content fruits (melon etc)
Ripe bananas White pasta Apple juice
Papaya Buckwheat black-eye peas
Rice cakes Pinto beans Green vegetables
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Lipids

• Triglycerides have the general elements C, H, O
  like carbs except they have much less O. They
  are made of glycerol and fatty acids.
• Glycerol is a small, 3-carbon molecule with three
  hydroxyl groups.

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Lipids

• Fatty acids are long molecules with a polar,
  hydrophilic end and a non-polar, hydrophobic
  "tail". The hydrocarbon chain can be from 14 to
  22 CH2 units long even number of C.

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Saturated Fats

• If there are no CC double bonds in the
  hydrocarbon chain, then it is a saturated fatty
  acid (i.e. saturated with hydrogen).
• These fatty acids form straight chains, and have
  a high melting point.
• Sources are animals
• butter and
• lard (solid at room temp.)

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Unsaturated Fats

• If there are CC double bonds in the hydrocarbon
  chain, then it is an unsaturated fatty acid (i.e.
  unsaturated with hydrogen).
• These fatty acids form bent chains, and have a
  low melting point.

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Unsaturated Fats

• Fatty acids with more than one double bond are
  called poly-unsaturated fatty acids (PUFAs).
• Cold blooded animals (fish) and plants are
  sources omega fatty acids, flax, olive oil,
  canola and sunflower oil.

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Triglycerides

• Triglycerides are insoluble in water.
• They are used for storage, insulation and
  protection in fatty tissue (or adipose tissue)
  found under the skin (sub-cutaneous) or
  surrounding organs.
• They yield more energy per unit mass than other
  compounds so are good for energy storage (about
  2X more energy).

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DIETARY CONSIDERATIONS

• In food chemistry, HYDROGENATED margarine is
  plant unsaturated fatty acid which has had H
  added back to its structure.
• This results in a margarine which is more solid
  and able to with-stand higher temperatures.
• Most unsaturated fats are liquids (olive oil,
  canola oil are liquid at room temperature).

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DIETARY CONSIDERATIONS

• TRANS FATS Unsaturated fats have a structure
  with kinks these kinks result in a liquid state
  at room temperature.
• In the early 20th century, a chemical process
  called hydrogenation was developed that converts
  vegetable oils into saturated, more solid fats
  (margarine and vegetable shortening).

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DIETARY CONSIDERATIONS

• When it was discovered that eating saturated
  fats increases the risk for coronary heart
  disease, the food industry turned to partial
  hydrogenation.
• This process lowered the content of saturated fat
  in vegetable shortening and margarine, but also
  dramatically increased the amount of a certain
  kind of fat - trans fat - in our diets, as an
  unavoidable side reaction.

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DIETARY CONSIDERATIONS

• While suppliers praised processed vegetable oils
  as healthy unsaturated and cholesterol-free
  substitutes for animal fats, there is now strong
  evidence that introducing trans-fatty acids into
  our diets does more harm than good.

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Saturated and Unsaturated Fats
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Phospholipids

• Phospholipids have a similar structure to
  triglycerides, but with a phosphate group in
  place of one fatty acid chain.
• There may also be other groups attached to the
  phosphate.

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Phospholipids

• Phospholipids have a polar hydrophilic "head"
  (the negatively-charged phosphate group) and two
  non-polar hydrophobic "tails" (the fatty acid
  chains).
• This mixture of properties is fundamental to
  biology, for phospholipids are the main
  components of cell membranes.

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Waxes

• Waxes are formed from fatty acids and long-chain
  alcohols.
• They are commonly found wherever waterproofing is
  needed, such as in
• leaf cuticles,
• insect exoskeletons,
• birds' feathers and
• mammals' fur.

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Waxes - Cholesterol

• CHOLESTEROL is like a fatty wax. Normally made
  in the liver, it is structural component of nerve
  tissue and cell membranes.
• It is also used to make various steroid hormones
  including progesterone, testosterone (sex
  hormones in females and males) estradiol, and
  cortisol.
• Bile salts are breakdown products of cholesterol.
  

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Waxes

• Blood is watery, and cholesterol is fatty. Just
  like oil and water, the two do not mix.
• To travel in the bloodstream, cholesterol is
  carried in small packages called lipoproteins.
• The small packages are made of fat (lipid) on the
  inside and proteins on the outside.
• Two kinds of lipoproteins carry cholesterol
  throughout your body.

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Waxes

• It is important to have healthy levels of both
• Low-density lipoprotein (LDL) cholesterol is
  sometimes called bad cholesterol.
• High amounts of LDL cholesterol leads to a build
  up of cholesterol in arteries.
• The higher the LDL level in your blood, the
  greater chance you have of getting heart disease.
  

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Waxes

• These form plaque along arteries.
• When it hardens the arteries we call it
  arteriosclerosis.
• These can dislodge to plug smaller arteries or
  veinsheart attacks or strokes are possible.
• They can completely block a vessel resulting in
  an embolism, aneurism, heart attack, stroke.

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Waxes

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Waxes

• High-density lipoprotein (HDL) cholesterol is
  sometimes called good cholesterol.
• HDL carries cholesterol from other parts of your
  body back to your liver.
• The liver removes the cholesterol from your body.
  
• The higher your HDL cholesterol level, the lower
  your chance of getting heart disease.

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The cholesterol numbers
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Things that TEND to increase LDL levels

• Overweight
• Physical inactivity
• Cigarette smoking
• Excessive alcohol use
• Very high carbohydrate diet
• Certain diseases and drugs
• Genetic disorders.

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What seems to be the population trend
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Proteins

• The polymer of amino acids does not remain like a
  long chain but folds into a three-dimensional
  shape which is the most stable for that sequence
  of amino acids.
• This shape is called the native conformation for
  that particular protein and is essential for that
  protein's biological activity. i.e. shape is
  everything

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Proteins

• The shape may be altered by various factors e.g.
  heat or large pH changes.
• Once the three-dimensional shape is altered,
  biological activity is lost.
• The building blocks of proteins are amino acids
• Contain nitrogen (as well as C, H and O)
• These are arranged in a very specific order
  determines shape

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Essential Non-Essential AAs

• As far as your body is concerned, there are two
  different types of amino acids
• essential and non-essential.
• Non-essential amino acids are amino acids that
  your body can create out of other chemicals found
  in your body.
• Essential amino acids cannot be created, and
  therefore the only way to get them is through
  food.

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Protein

• Protein in our diets comes from both animal and
  vegetable sources. Most animal sources (meat,
  milk, eggs) provide what's called "complete
  protein," meaning that they contain all of the
  essential amino acids.
• Vegetable sources usually are low on or missing
  certain essential amino acids. For example, rice
  is low in isoleucine and lysine.

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Balancing AAs

• However, different vegetable sources are
  deficient in different amino acids, and by
  combining different foods you can get all of the
  essential amino acids throughout the course of
  the day.
• This balancing of amino acids is essential
  because if one amino acid is deficient, an entire
  protein cannot be made sufficiently.

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Vegetarian Diets

• Vegetarians need to balance plant source
  proteinseg. Rice with beans.
• Some vegetable sources contain quite a bit of
  protein -- things like nuts, beans, soybeans,
  etc. are all high in protein. By combining them
  you can get complete coverage of all essential
  amino acids.

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Types of Vegetarian Diets

• Pescatarian may include fish but no chicken,
  beef, pork
• Flexitarian may include some meat time to time
• Lacto-Ovo vegetarian includes milk products and
  eggs but no meats
• Vegan do not include any animal products
  including processed foods that may include animal
  products like gelatine, honey.

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To Get Protein RDA

• The digestive system breaks all proteins down
  into their amino acids so that they can enter the
  bloodstream.
• Cells then use the amino acids as building
  blocks.

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• This photo is the
• Nutritional Facts label
• from a can of tuna.
• According to the RDA (Recommended Daily
  Allowance) for protein is 0.36 grams of protein
  per pound of body weight. So a 150-pound person
  needs 54 grams of protein per day.
• From this you can see that your body cannot
  survive strictly on carbohydrates. You must have
  protein.

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Nutritional label from a can of tuna fish

• You can see that a can of tuna contains about 32
  grams of protein (this can has 13 grams per
  serving and there are 2.5 servings in the can).
• A glass of milk contains about 8 grams of
  protein.
• A slice of bread might contain 2 or 3 grams of
  protein.
• You can see that it is not that hard to meet the
  RDA for protein with a normal diet.

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Role of Insulin

• Insulin is a simple protein in which two
  polypeptide chains of amino acids are joined by
  disulfide linkages.
• It transfers glucose into cells to produce energy
  for the body.
• In adipose (fat) tissue, insulin facilitates the
  storage of glucose and its conversion to fatty
  acids.

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Role of Insulin

• Insulin also slows the breakdown of fatty acids.
• In muscle it promotes the uptake of amino acids
  for making proteins.

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Role of Insulin

• In the liver it helps convert glucose into
  glycogen (the storage carbohydrate of animals)
  and it decreases gluconeogenesis (the formation
  of glucose from noncarbohydrate sources like fat
  or protein).
• The action of insulin is opposed by glucagon,
  another pancreatic hormone, and by epinephrine.

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If glucose levels remain high, the liver

• stores the sugars as glycogen (animal starch).
• If the glycogen is not used up, it further
  metabolizes glycogen into fatty acids and fat
  molecules.
• These are transported around the body in blood
  vessels and lymphatic vessels and is stored in
  ADIPOSE tissue (fat tissue) until needed.

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If glucose levels remain high, the liver

• This provides smoothness under the skin,
  protection, and a secondary source of energy when
  needednot all fat is bad.
• If we dont use it regularly though, it builds up
  into unhealthy situations such as fatty tissue
  around the heart and in the blood vessels. (Long
  Term Storage)

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Disposal by Various Tissues of a Hypothetical
Meal Containing 100 g of Glucose
http//www.medscape.com/infosite/diabetes_educatio
n/article-3
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Extreme starvation situations (dieting)

• After immediate energy sources are used (like
  carbohydratesincluding stored glycogen converted
  to blood sugar), fat reserves are used.
• After fat reserves are used, the body begins to
  call-up proteins. Proteins are converted into
  an energy source as a last resort.

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Extreme starvation situations (dieting)

• This is damaging to our protein rich tissues
  (muscles, hair, nails) and we notice the
  differences in our eyes, nails, hair and skin
  texture.
• It also damages skeletal muscles and heart
  muscle. These damages are not easily reversed by
  proper dieting later.

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PRIORITIZED SOURCES OF ENERGY

• Sugars
• Fats
• Proteins
• This site slightly detailed metabolic pathways
  that describe biochemical processes in
  metabolism
• http//users.humboldt.edu/rpaselk/BiochSupp/Pathwa
  yDiagrams/PathIndex.html

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http//users.humboldt.edu/rpaselk/BiochSupp/Pathwa
yDiagrams/StagesCat.gif
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1991 study published in the "The American Journal
of Clinical Nutrition"

• Showed that patients following a very low-calorie
  diet
• lost lean body mass and experienced a decrease in
  metabolic rate after only three days.
• Then, 21 days after the start of the diet,
  participants experienced an 18 percent decrease
  in metabolism and lean body mass, on
  average.Read more http//www.livestrong.com/arti
  cle/486748-dieting-muscle-atrophy/ixzz1eyOOO3A7

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GENERAL PRINCIPLES OF WEIGHT CONTROL

• Body weight is always the result of a simple
  equation. Input vs. Output Body Weight
• Input refers to the amount of food consumed.
• Output refers to the amount of energy expended.

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GENERAL PRINCIPLES OF WEIGHT CONTROL

• Therefore, if Output Input you will maintain
  your present weight.
• If Input is less than Output you will lose
  weight. If Input is greater than Output you will
  gain weight.
• There is no short cut to weight loss.
• One pound of body weight 3,500 kcal or
  32,000kj.

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GENERAL PRINCIPLES OF WEIGHT CONTROL

• In order to reduce body weight you must do one of
  the following
• Decrease food intake
• Increase activity
• Do a combination of both (this is most effective)

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The problem with diets

• Nutrition
• Abnormal (not a lifestyle change)
• Loss of muscle mass
• E.g. -A person who diets and loses 10 lbs. loses
  both fat and muscle tissue.
• -When these 10 lbs are regained they are in the
  form of just fat tissue.
• -The person now has more fat tissue than before
  the diet even though their weight is the same as
  at the outset.

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GENERAL PRINCIPLES OF WEIGHT CONTROL

• All weight loss is the result of a loss in
  muscle and fat tissue.
• To offset this loss of muscle mass exercise must
  accommodate any weight loss program.
• An increase in exercise does two things to aid in
  weight loss
• It increases caloric expenditure.
• It increases metabolism by increasing muscle mass
• i.e. A larger engine burns more fuel.

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A recommended program would be

• Decreasing intake by 200 kcal/day
• Increasing activity by 300 kcal/day
• 500 kcal/day 3,500 1 lb/wk.
• Any successful weight loss program must be a
  lifestyle change not a fad.
• Exercise must accommodate diet in order to offset
  muscle loss and increase metabolism.