Chapter 36 – Nutrition
Principles of Nutrition:
o Nutrition – study of intake of food and how it nourishes the body
o Nutrients – specific biochemical substances used by the body for:
o Growth
o Development
o Activity
o Reproduction
o Lactation
o Health maintenance
o Recovery from illness / injury
o Nutrient needs change based in response to body’s change in size, activity, growth, development,
and state of health
o Essential Nutrients – not synthesized in the body // made in insufficient amounts
o Macronutrients – supply energy and build tissue
 Carbohydrates
 Fats
 Proteins
o Micronutrients – vitamins // minerals
 Smaller amounts
 Regulate and control body processes
o Nonessential Nutrients – do not have to be supplied in diet or w/ supplements
o Either not required for body functioning // are synthesized in adequate amounts in body
o Conversion of nutrients
o Excess carbs / proteins  fat  stored as triglycerides
Six Classes of Nutrients:
Supply energy:
1. Carbohydrates
2. Protein
3. Lipids (fats)
Regulate Body Processes:
1. Vitamins
2. Minerals
3. water
Energy Balance:
o Energy is derived / obtained from foods consumed
o Energy in the body is used to carry on any kind of activity, whether voluntary or involuntary.
o A person’s total daily energy expenditure is the sum of all the calories used to perform physical
activity, maintain basal metabolism, and digest, absorb, and metabolize food.
Metabolic Requirements:
o Basal metabolism – energy required to carry out involuntary activities while body is at rest
o Energy needed to sustain metabolic activities of cells and tissues
o Examples:
o Maintaining body temperature
o Maintaining muscle tone
o Producing and releasing secretions
o Propelling food through GI tract
o Inflating the lungs
o Contracting the heart muscles
o Men have higher BMR due to larger muscle mass
o Factors that inc. BMR:
o Growth
o Infections
o Fever
o Emotional tension
o Extreme environmental temperatures
o Elevated levels of hormones
 Epinephrine
 Thyroid hormones
o Factors that dec. BMR:
o Aging
o Prolonged fasting
o Sleep
IBW: ideal body weight
BMI: body mass index
o Indicator of total body fat stores in the general population
o Indicates risk for diseases
o Heart disease
o Diabetes
o hypertension
BMI Scale:
o Underweight
o Below 18.5
o Healthy
o 18.5 – 24.9
o Overweight
o 25 – 29.9
o Obesity
o 30 or greater
o Extreme obesity
o 40 or greater
o
BOX 36-1
BMI-for-Age Percentile (Children and Teens)
L Less than 5th percentile
U Underweight
5 5th percentile to less than the 85th percentile
H Healthy weight
8 5th percentile to less than the 95th percentile
O Overweight
9 5th percentile or greater
OObese
Carbohydrates:
o Sugars // Starches
o Organic compounds composed of:
o Hydrogen
o Oxygen
o Most abundant // least expensive source of calories in the diet
o Carbohydrates are correlated to income
o Higher income  less consumption of carbs
o
Classification / Metabolism:
o Simple
o Monosaccharide
o Disaccharide
o Complex
o Polysaccharide
o Easily and quickly digested compared to protein and fat
o 90% intake is digested
o % decreases as fiber intake increases
o Carbohydrates  glucose for transport through blood or energy use
o Glucose is transported from GI tract, through portal vein, to the liver
o Liver stores glucose and regulates its entry into blood
o Insulin // glucagon
o Responsible for keeping serum glucose constant during feasting and fasting
o Cells burn / oxidize glucose creating:
o Energy
o Carbon dioxide
o Water
o Glucose burns completely – no biproduct for kidneys to excrete
o high glucose // more than needed for energy  stored
o glycogen stores deficient  glucose is converted to glycogen and stored (glycogenesis)
o glycogen is broken down in time of need to supply glucose (glycogenolysis)
o adequate storage of glucose  converted to fat
Function:
o supply energy
o 4 calories for gram
o Recommended amount: 45-65% of total calories for adults
o Complex carbohydrates is the focus
Protein:
o Formation of all body structures
o Genes
o Enzymes
o Muscle
o Bone matrix
o Skin
o Blood
o Complete protein = animal protein or plant protein + small amount of animal
protein or two complementary vegetable proteins.
Classification / Metabolism:
o Complete
o High quality
o Examples:
 Eggs
 Dairy products
 Meats
 soy
o
o Incomplete
o Low quality
o Examples:
 Grains
 Legumes
 Vegetables
o Dietary protein is broken down into amino acid particles by pancreatic enzymes in the small
intestine. These are absorbed through the intestinal mucosa to be transported to the liver. In the
liver, amino acids are recombined into new proteins or are released into the bloodstream for use in
protein synthesis by tissues and cells. Excess amino acids are converted to fatty acids, ketone
bodies, or glucose and are stored or used as metabolic fuel.
Broken down: catabolism
Replaced: anabolism
o Nitrogen balance, a comparison between catabolism and anabolism, can be measured by
comparing nitrogen intake (protein intake) and nitrogen excretion (nitrogen lost in urine, urea,
feces, hair, nails, skin).
o Nitrogen intake = nitrogen excretion neutral nitrogen balance
o Nitrogen intake > nitrogen excretion  positive nitrogen balance
o Positive indicates tissue growth
 Childhood
 Pregnancy
 Lactation
 Recovery from illness
o Nitrogen intake < Nitrogen excretion negative nitrogen balance
o Negative indicates tissue is breaking down faster than its getting replaced
 Starvation
 Catabolism immediately following surgery
 Illness
 Trauma
 Stress
Function:
o Maintain body tissues that break down from normal wear and tear
o Support the growth of new tissue
o Nitrogen remaining after metabolism burdens the kidneys
o Energy is used to excrete nitrogen
o Protein consumed in excess is stored as fat
o Protein intake:
o 10-35% total caloric intake
Fats:
o Insoluble in water / blood
o Composed of:
o Carbon
o Hydrogen
o Oxygen
o 95% of lipids in diet are in form of triglycerides
o Predominant form of fat in food and major storage form of fat in the body
o Compound lipids:
o Phospholipids
 Lipid is combined with another substance
o Derived lipids:
o Cholesterol
 Constitute the remainder of the lipids ingested
Classification / metabolism:
o Saturated fats
o Contain more hydrogen than unsaturated fats
o Solid at room temperature
o Animal fats
o Raise serum cholesterol levels
o Unsaturated fats
o Vegetable fats
o Liquid at room temperature
 Oils
o Lower serum cholesterol levels
o Trans-fat
o Hydrogenate liquid oils
 More solid and more stable
o Raises serum cholesterol
 Can be counted as saturated fats for the day
Cholesterol:
o Fat-like substance in animal products
o Non-essential
o Abundant in brain and nerve cells
o Synthesizes bile acids
o Precursor of the steroid hormones and vitamin d
o Risk factors:
o Atherosclerosis
o Lower serum cholesterol
o Limit cholesterol intake
o Eat less total fat
 Saturated and trans
o Increase fiber
Metabolism:
o Digestion occurs largely in the small intestine
o Bile – secreted by the gallbladder – emulsifies fat to increase the surface area so that pancreatic
lipase can break down fat effectively
o Most fats are absorbed into lymphatic circulation by protein carrier
o Transported to the liver
Functions:
o Most concentrated source of energy in the diet
o 9 calories per gram
o Fat makes food taste better to your palate
o Stomach is full longer b/c delayed gastric emptying time
o Fat aids in absorption of fat-soluble vitamins and provides:
o Insulation
o Structure
o Temperature control
o Limit intake of saturate fats and trans fats < 10% of calories per day
Regulatory Nutrients:
Vitamins:
o Organic compounds needed by the body in small amounts
o Do not provide energy but are needed for metabolism of carbs, lipids, and proteins
o Essential in diet b/c they are not synthesized in the body or are made in insufficient quantities
o Vitamins can be destroyed by light, heat, air, and during preparation
o Fresh foods = higher in vitamins
o Fortification
o Vitamin is not naturally occurring in a food and so it’s added
o Classification:
o Water soluble
 Vitamin c
 B-complex vitamins
 Ascorbic acid
 Thiamin
 Riboflavin
 Niacin
 Pyridoxine
 Biotin pantothenic acid
 Folate
 Cobalamin
 Absorbed through intestinal wall directly into bloodstream
 Water soluble vitamins are not stored in the body
o fat soluble
 Vitamins A, D, E, K
 Absorbed w/ fat into lymphatic circulation
 Must be attached to protein to be transported through the blood
 Body stores excess in liver and adipose tissue
 Excessive intake of vitamins A and D can be toxic
Minerals:
o Inorganic
o All body fluids and tissues in the form of salts (sodium chloride) or inorganic compounds (iron in
hemoglobin)
o Functions:
o Provide storage within the body
o Regulate body processes
o Not broken down or rearranged
o Form of ash that remains after digestion
o Macrominerals
o Bulk minerals
o Needed by the body in amounts greater than 100mg/day
o Include:
 Calcium
 Phosphorus
 Sulfur
 Sodium
 Chloride
 Potassium
 Magnesium
o Microminerals
o Trace elements
o Less than 100 mg/day
o Include:
 Iron
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Zinc
Manganese
Chromium
Copper
Molybdenum
Selenium
Fluoride
Iodine
Digestion
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Digestion begins in the mouth where food is taken in, mixes with saliva, is pushed into the
pharynx by the tongue, and then continues into the esophagus.
Peristalsis moves the food through the esophagus and into the stomach.
The stomach churns the ingested food, mixing it with substances to break down the food and
convert it to a semiliquid mixture.
The food leaves the stomach and enters the small intestine.
The small intestine secrets enzymes, which, along with secretions from the liver and
pancreas, digest the food.
The digested nutrients are then transferred into the person’s circulation (absorption), to be
transported throughout the body. Most absorption of digested food and minerals, and some
absorption of water, occurs through the walls of the small intestine.
Undigested waste materials continue through the GI tract and are eliminated.