HUMAN NUTRITION

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HUMAN NUTRITION
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The basic nutritional needs

• Supply energy and raw materials for activities
  and processes in the body
• Macronutrients - required in large amounts
• carbohydrates
• proteins
• fats
• Micronutrients - required in small amounts
• vitamins
• minerals

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Uses of macronutrients

• Carbohydrates and fats used as a source of energy
  (protein can also be used for this)
• Proteins provide the raw materials, or building
  blocks, required for the synthesis of essential
  metabolites, growth, and tissue maintenance - to
  make human proteins
• Carbohydrates and proteins 4 calories/gram
• Fat 9 calories/gram

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Carbohydrates

• Monosaccharides
• Simple sugars
• Building block of more complex carbohydrates
• Glucose - the most abundant
• Disaccharides
• Polysaccharides
• starch, glycogen
• cellulose

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Glucose

• During digestion other carbohydrates are broken
  down or converted to glucose
• Transported by the blood to all the cells in the
  body
• Within cells, respiration breaks down glucose to
  produce energy necessary to sustain life

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Other monosaccharides

• Fructose and galactose have the same chemical
  make up as glucose, C6H12O6, differing only in
  the arrangement of the atoms
• Converted into glucose and metabolized
• High fructose corn syrup, often preferred because
  sweeter than sucrose

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Disaccharides

• Two monosaccharides chemically joined
• Sucrose - most common (glucose and fructose)
• Table sugar at least 97 pure sucrose
• Supplies only calories - no other nutritional
  value
• During digestion broken into glucose and
  fructose
• Other disaccharides
• Lactose - milk sugar (glucose and galactose)
• Maltose (2 glucose molecules) - germinating grains

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Polysaccharides

• Also known as complex carbohydrates
• Hundreds to thousands of sugar units
• Glucose is the only monosaccharide
• Distinguished by the way in which the glucose
  units are joined together, their arrangement, and
  their number

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Starch

• Storage form of glucose found in plants
• Seeds, some fruits, tubers, and tap roots
• Starch in foods can be traced directly to plant
  origin starch in bread or pasta from wheat
• Starch in the human diet
• Grains (wheat, rice, and corn)
• Underground crops (potato, sweet potato,
  cassava)
• Legumes (beans and peas)
• Broken down into glucose by enzymes

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Glycogen

• Body's storage form of glucose in liver and
  skeletal muscles
• Excess glucose is stored as glycogen
• Only a days worth of glycogen is stored
• Carbohydrate loading eat lots of starchy foods
  to build glycogen reserves
• Excess glucose beyond this is generally converted
  to fat

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Fiber - other polysaccharides

• From plant sources
• Not digestible - provides bulk and other benefits
• Fruits, vegetables, seeds and whole grains supply
  most of the fiber in the human diet.

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Types of dietary fiber

• Cellulose
• Lignin
• Hemicellulose
• Pectin

• Gums
• Mucilages
• Others

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Cellulose

• Principal component of plant cell walls
• Composed of glucose
• Humans do not have the enzymes to break the bonds
  connecting the glucose molecules in cellulose
• Passes through the digestive tract as roughage

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Other fibers

• Pectins and hemicelluloses - also cell wall
  polysaccharides
• Pectins also occur in the middle lamella
• Gums and mucilages are exudates from plants that
  are used commercially as thickening agents
• Polysaccharides from red and brown algae are also
  dietary fiber

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Dietary fiber grouped into two types

• Soluble and insoluble - relates to their
  solubility in water
• Insoluble fiber includes cellulose and lignin and
  some hemicelluloses
• Soluble fiber includes other hemicelluloses,
  pectins, gums, mucilages, and algal
  polysaccharides

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Soluble fiber Insoluble fiber

• Wheat bran
• Largely cellulose
• No cholesterol lowering ability
• Effective in speeding passage of food through the
  large intestines
• May reduce the risk of colon cancer

• Gum in oat bran
• Pectin in apples
• Believed to lower cholesterol levels in the blood

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Proteins and essential amino acids

• Proteins are large complex molecules composed of
  amino acids
• 20 naturally occurring amino acids
• Thousands of different types of proteins
• During digestion proteins in our food are broken
  down into the component amino acids by enzymes in
  the digestive tract and transported in the blood
  stream

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Functions of Proteins

• Type Protein Function Examples
• Structural Support Collagen and
  keratin
• Enzymes Catalysts Digestive enzymes
• Hormones Regulation Insulin
• Transport Transport Hemoglobin
• substances
• Storage Storage of Ovalbumin in
  egg white
• amino acids
  Casein in milk
• Contractile Movement Actin, myosin -
  muscles
• Defensive Protection Antibodies

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Essential Amino Acids

• Role of dietary protein is to supply amino acids
  for the body to make human proteins
• All 20 amino acids are necessary for protein
  synthesis
• Human body can synthesize 11 amino acids
• Other nine cannot be made by the body and must
  come from the diet
• These nine are called essential amino acids

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Essential Amino Acids

• Cannot be stored by the body at all
• They must be present simultaneously in the diet
• It is critical to receive all the essential amino
  acids in each meal
• Persistent lack of these essential amino acids
  results in protein deficiency

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Complete proteins

• Complete proteins contain all the essential amino
  acids and in the right proportions
• Almost all proteins derived from animals are
  complete proteins
• Proteins derived from plants are usually
  incomplete, deficient in one or more essential
  amino acids

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Complementary plant proteins

• Combining complementary plant proteins can supply
  all essential amino acid
• Traditional diet of the Mexican Indians, beans
  and corn, contains complementary proteins
• The beans are low in methionine but adequate in
  tryptophan and lysine
• Corn is poor in tryptophan and lysine but
  contains adequate amounts of methionine

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Essential and Nonessential Amino Acids

• Essential Nonessential
• Histidine Alanine
• Isoleucine Asparagine
• Leucine Aspartic Acid
• Lysine Arginine
• Methionine Cysteine
• Phenylalanine Glutamic Acid
• Threonine Glutamine
• Tryptophan Glycine
• Valine Proline
• 
  Serine
• 
  Tyrosine

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How much protein do we need?

• Nutritional recommendations can be based on two
  criteria
• 12 of the total calories consumed should be from
  proteins (1500 calories diet - 45 grams of
  protein 1800 calories - 54 g 2000 cal - 60 g)
• 0.8 g/kg body weight (person weighing 150 lbs -54
  g protein person weighing 100 lbs - 36 g
  protein 200 lbs - 72 g protein

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How much protein in our food?

• 1 ounce meat - 7 grams protein
• 4 ounces turkey - 28 grams protein
• 1 ounce cheese - 7 grams protein
• 1 glass milk - 8 grams protein
• 1/2 cup beans - 6 grams protein
• 1 slice whole wheat bread- 4 grams protein
• 1 egg - 8 grams protein
• 2 TBSP peanut butter - 8 grams protein
• 1 serving oatmeal - 5 grams protein

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Malnutrition

• Chronic hunger and malnutrition are problems in
  many developing nations
• Estimates 15 to 20 of the world's population
  (around one billion people) suffer from
  undernutrition or malnutrition
• Approximately 20 million deaths each year
• Undernutrition is defined as an insufficient
  number of calories to maintain daily energy
  requirements
• Malnutrition is a quality deficiency in which one
  or more essential nutrients is lacking even
  though enough calories

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Kwashiorkor

• Protein deficient but sufficient calories
• Prevalent after weaning when a child no longer
  receives protein-rich breast milk and is switched
  to a starchy diet low in protein
• Symptoms of kwashiorkor
• puffy skin
• swollen belly due to edema
• reddish-orange cast to the hair
• dermatitis and listlessness.

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Marasmus

• Results from starvation
• Diet is low in calories and protein
• Sufferers extremely thin and shriveled (literally
  skin and bones)
• Muscles of the body, even the heart muscle, are
  wasted away as muscle protein is used to supply
  energy needs

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Treatment

• Symptoms of both marasmus and kwashiorkor can be
  reversed if treated in time
• In infants and young children, mild mental
  retardation and stunted growth may be permanent
  results

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Vegetarian Diets

• Ovo-lacto vegetarian
• Lacto vegetarians
• Vegans
• Major difficulty is getting sufficient protein
• Balance amino acids to avoid protein deficiency

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Fats

• One category of lipid
• Lipids are a diverse group of compounds with a
  common characteristic of insolubility in water
• Some fat is necessary in the diet - several vital
  functions

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Functions of Lipids

• Type of Lipid Function Examples
• Triglyceride Energy Animal fat
• storage Vegetable
  oils
• Insulation Subcuta
  neous fat
• Steroid Structural Cholesterol in
  membranes
• Regulation
  Cortisol, Estrogen,
• 
  Testosterone
• Phospholipid Structural Phosphatidylcholine
  in cell membranes
• 
  

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Triglycerides

• Fats and oils
• 95 of lipids in foods
• Formed from glycerol and 3 fatty acids

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Fatty acids

• Simplest type of lipid
• Building blocks for triglycerides and
  phospholipids
• Body can synthesize most fatty acids
• Three must be supplied in the diet
• Linoleic acid
• Linolenic acid
• Arachidonic acid

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Fatty acid

• Carbon chain with hydrogen attached
• Different fatty acids vary in the number of
  carbon and hydrogen atoms
• Saturated or unsaturated
• Saturated fatty acids have all single bonds
  between carbon atoms
• Unsaturated fatty acids have one or more double
  bonds

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Saturated Fatty Acid
H H H H H H H H H H H
H H H H l l l l l
l l l l l l l l
l l O H - C - C - C - C - C - C - C -
C - C - C - C - C - C - C - C - C-OH l
l l l l l l l l
l l l l l l H H H
H H H H H H H H H H H H

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Monounsaturated Fatty Acid
H H H H H H H H H H H
H H H H l l l l l
l l l l l l l l
l l O H - C - C - C - C - C - C C -
C - C - C - C - C - C - C - C - C-OH l
l l l l l l
l l l l l l H H H
H H H H H H H H H H

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Polyunsaturated Fatty Acid
H H H H H H H H H H H
H H H H l l l l l
l l l l l l l l
l l O H - C - C - C - C - C C - C -
C - C - C C - C - C - C - C - C-OH l
l l l l l l
l l l l H H H
H H H H H H
H H

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Triglycerides

• Glycerol backbone is common to all
• Many types of fatty acids occur
• Nature of the fatty acids determines the
  properties of the triglyceride

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Saturated Fat
C-O-C-C-C-C-C-C-C-C-C-C-C-C-
C-C-C-C-C l C-O-C-C-C-C-C-C-C-C-C-C-C-C-C-C-C-C-C
l C-O-C-C-C-C-C-C-C-C-C-C-C-C-C-C-C-C-C
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Monounsaturated Fat
C-O-C-C-C-C-C-C-C-C-C-C-C-C-
C-C-C-C-C l C-O-C-C-C-C-C-C-CC-C-C-C-C-C-C-C-C-C
l C-O-C-C-C-C-C-C-C-C-C-C-C-C-C-C-C-C-C
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Polyunsaturated Fat
C-O-C-C-C-C-C-C-CC-C-C-C-C-
C-C-C-C-C l C-O-C-C-C-C-C-C-CC-C-C-C-C-C-C-C-C-C
l C-O-C-C-C-C-C-C-CC-C-C-C-C-C-C-C-C-C
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Fats in Foods

• Contain a mixture of both saturated and
  unsaturated fatty acids
• Saturated fats - contain mostly saturated fatty
  acids
• solid at room temperature - animal fats such as
  lard, butter, and beef fat
• Vegetable oils - generally composed of
  unsaturated fatty acids
• liquid at room temperature

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Vegetable Oils

• Oils with monounsaturated fatty acids
• olive oil, peanut oil, and canola oil
• Oils with polyunsaturated fatty acids
• corn oil, soybean oil, and safflower oil
• Saturated fats in plants
• coconut oil, palm oil, and cocoa butter
• consist mostly of saturated fatty acids

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Hydrogenation

• In prepared foods with vegetable oils
• Unsaturated oil has been chemically modified by
  hydrogenation
• Adds hydrogen making an unsaturated oil, a
  saturated fat
• Converts a liquid oil into a solid fat - margarine

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Saturated vs. unsaturated fats

• Diets high in saturated fats have been implicated
  in colon, breast, and prostate cancers
• Saturated fats increase blood cholesterol levels
  and are linked to cardiovascular disease
• Unsaturated fats lower the risk of cardiovascular
  disease by lowering blood cholesterol levels

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Cholesterol

• Type of lipid known as steroid
• lipid containing four carbon rings
• Vital component of cell membranes
• therefore needed by all cells
• Used in the synthesis of sex hormones and several
  other hormones

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Cholesterol

• Synthesized in liver from saturated fatty acids
  and absorbed from animal foods
• If the diet is high in saturated fats, even if it
  is low in cholesterol, the liver responds by
  increased cholesterol synthesis
• Lipoproteins HDL and LDL
• LDL - bad cholesterol causing deposits in
  arteries and leading to heart attacks and strokes

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Cholesterol

• Diets high in cholesterol and/or saturated fat
  contribute to high blood cholesterol levels
  especially LDLs
• Unsaturated fats lower blood cholesterol levels
• Polyunsaturated fats lower all cholesterol levels
  including HDLs
• Monounsaturated fats lowering total and LDL levels

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Micronutrients

• Essential for proper nutrition
• Required in very small amounts
• Deficiency symptoms develop when nutrient is
  lacking
• Comprise only 1 to 2 of the dry weight
• There are two categories
• organic compounds - vitamins
• inorganic compounds - minerals

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Dietary guidelines

• 1. Consume only as much energy (kcal) as is
  expended
• 2. Increase consumption of complex carbohydrates
  and "naturally occurring" sugars from 28 of
  energy intake to 48
• 3. Reduce consumption of refined and processed
  sugars to account for about 10 of total energy
  intake

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Dietary guidelines (contd)

• 4. Reduce fat consumption from approximately 40
  to about 30
• 5. Reduce saturated fat consumption to about 10
  of energy intake polyunsaturated and
  monounsaturated fats, should each account for 10
  
• 6. Reduce cholesterol consumption to about 300 mg
  a day
• 7. Limit sodium intake to about 5 g a day

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Nutrition Facts Serving Size 1/2 (127
g) Servings Per Container About 3.5
Amount per Serving
Calories 100 Calories from Fat 0
Daily Value
Total Fat 0g 0
Saturated Fat 0g 0 Cholesterol
0mg 0 Sodium 580mg
24 Total Carbohydrates 19g 6 Dietary
Fiber 5g 20 Sugars 3g Protein
6 g 12
Vitamin A 0 Vitamin C 0 Calcium 2
Iron 8