Hole’s Human Anatomy
and Physiology
Twelfth Edition
Shier w Butler w Lewis
Chapter
18
Nutrition
and Metabolism
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
1
18.1: Introduction
• The human body requires fuel as well as materials to develop, grow and
heal
• Nutrients are chemical substances supplied by the environment required
for survival
• Macronutrients
• Carbohydrates
• Proteins
• Fats
• Micronutrients
• Vitamins
• Minerals
• Essential nutrients
• Nutrients human cells cannot synthesize such as certain amino
acids
2
3
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Release into
bloodstream
Bloodstream
Stimulation
Inhibition
Adipocytes synthesize
fat and secrete leptin
into bloodstream
+
Leptin increases
metabolic rate.
+
Fat cells
–
Leptin inhibits neuropeptide
Y release from the
hypothalamus
Food intake in excess
of caloric needs
excessive
Appetite suppressed
–
Appetite
+
insufficient
Fasting
Appetite enhanced
Ghrelin stimulates release
of neuropeptide Y from
the hypothalamus
+
+
Cells in stomach
secrete ghrelin
Bloodstream
4
18.2: Carbohydrates
• Carbohydrates are organic compounds and include the
sugars and starches
• The energy in their chemical bonds are used to power
cellular processes
• Excesses lead to:
• Obesity
• Dental caries
• Nutritional deficits
• Deficiencies lead to:
• Metabolic acidosis
• Weight loss
5
Carbohydrate Sources
• Carbohydrates are ingested in a variety of forms:
• Complex carbohydrates are polysaccharides that include:
• Starch from plant foods
• Gylcogen from meats
• Simple carbohydrates are:
• Dissaccharides from milk sugar, cane sugar, beet
sugar and molasses
• Monosaccharides from honey and fruits
• Digestion breaks complex carbohydrates into
monosaccharides that are small enough to be absorbed
• Cellulose is a complex carbohydrate abundant in our food
• It is not digested, but provides bulk (fiber or roughage)
6
Carbohydrate Use
• Monosaccharides that are absorbed include fructose,
galactose, and glucose
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Carbohydrates
Starch
Sucrose
Maltose
Lactose
Digestion
Glucose
Glucose
and
Fructose
Glucose
Glucose
and
Galactose
Monosaccharides
(Respiration)
(Glycogenesis)
(Lipogenesis)
CO2 + H2O + Energy
Glycogen
Fat
7
Carbohydrate Requirements
• The minimal requirements for carbohydrates in the human
diet is unknown
• Intake of at least 125 – 175 grams is necessary
• An average diet includes 200-300 grams
8
18.3: Lipids
• Lipids are organic compounds that include fats, oils, and fatlike substances such as phospholipids and cholesterol
• They supply energy for cellular processes and help to build
structures like cell membranes
• The most common dietary lipids are fats called triglycerides
• Excesses lead to:
• Obesity
• Increased serum cholesterol
• Increased risk of heart diseases
• Deficiencies lead to:
• Weight loss
• Skin lesions
• Hormonal imbalances
9
Lipid Sources
• Triglycerides are found in plant-based and animal-based
foods and include:
• From plants:
• Seeds, nuts and plant oils (olive, peanut and canola
are the healthiest)
• From animals:
• Meat, eggs, milk and lard
10
Lipid Use
• Lipids in foods are phospholipids, cholesterol and most
commonly, fats (triglycerides)
• They are oxidized for energy
• They are stored in adipose tissue
• Glycerol may be used to synthesize glucose
11
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Fats from foods
Hydrolysis
Glucose
Glycerol
Fatty acids
+
Fat
Ketone bodies
Beta oxidation
Acetyl coenzyme A
Citric
acid
cycle
Energy
+
CO2
+
H2O
12
ATP
Heat
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Triglycerides
Digestion
Fatty acids + Glycerol
Triglycerides
Lipoproteins
Fatty acids
(except essential
fatty acids)
Cholesterol
Phospholipids
13
Lipid Requirements
• The lipid content of human diets varies widely
• The American Heart Association advises that the diet not
exceed 30% of total daily calories from fat
14
18.4: Proteins
• Proteins are polymers of amino acids
• They have a wide variety of functions, including building
more protein (structural protein, enzymes, hormones, and
plasma proteins) and supplying energy
• The waste product of protein metabolism is urea
• Excesses lead to obesity
• Deficiencies lead to:
• Extreme weight loss
• Muscle wasting
• Anemia
• Growth retardation
15
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Protein
Digestion
Amino acids
Proteins
Energy + CO2 + H2O
Structural
proteins
Enzymes
Hormones
Glucose
Fat
Plasma
proteins
16
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Proteins from foods
Hydrolysis
Amino acids
Deamination
Deaminated portions
(by various pathways)
+
–NH2 groups
Urea
Acetyl
coenzyme A
Fat
Glucose
Citric
acid
cycle
Energy
+
CO2
+
H2O
17
ATP
Heat
Protein Sources
• Foods rich in proteins include:
• Meats
• Fish
• Poultry
• Cheeses
• Nuts
• Milk
• Eggs
• Cereals
• To some degree legumes (beans and peas)
• The body needs 20 types of amino acids; those that can
be synthesized by the body are non-essential amino acids
(12) and those that cannot are essential amino acids (8)
18
Nitrogen Balance
• In healthy adults, protein is continuously built up and broken
down
• Proteins contain a high percentage of nitrogen
• The amount of nitrogen taken in is equal to amount excreted
• Negative nitrogen balance develops from starvation
• Positive nitrogen balance develops in growing children,
pregnant women, or an athlete in training
19
Protein Requirements
• In addition to supplying essential amino acids, proteins
provide nitrogen and other elements for the synthesis of nonessential amino acids and certain non-protein nitrogenous
substances
• The dietary amount varies according to body size, metabolic
rate, and nitrogen balance condition
• Typically protein intake is 10% of a person’s diet
• Most people should consume 60-150 grams a day
20
21
18.5: Energy Expenditures
• Carbohydrates, fats and proteins supply energy for all
metabolic processes
• Deficiencies can lead to death
• Excesses can lead to obesity
22
Energy Values of Food
• A calorie indicates the amount of potential energy a food
contains
• Calories can be measured from the content of foods
• The rate that the body expends energy can be measured
and is known as basal metabolic rate (BMR)
• This varies for:
• Carbohydrates
• 4.1 calories per gram
• Lipids
• 9.5 calories per gram
• Proteins
• 4.1 calories per gram
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Electric wires
for ignition
of sample
Thermometer
Oxygen
Food sample
Stirrer
Platinum dish
Water
Insulation
23
24
Energy Requirements
• Basal metabolic rate (BMR):
• The rate at which body expends energy at rest
• This primarily reflects energy needed to support the
activities of the organs
• This varies with gender, body size, body temperature,
and endocrine function
• Energy is needed:
• To maintain BMR
• To support muscular activity
• To maintain body temperature
• For growth in children and pregnant women
25
Energy Balance
• Energy balance occurs when caloric intake in the form of
food equals caloric output from BMR and muscular activities
• The body weight remains constant
• If, however, caloric intake exceed output, tissues store
excess nutrients
• This is a positive energy balance that leads to weight gain
26
Desirable Weight
• Most common nutritional disorders involve caloric
imbalances
• Desirable weight is difficult to determine
• Body Mass Index (BMI) is used today to assess weight
considering height
• A person is classified with BMI as either underweight,
normal weight, overweight, or obese
• Overweight is defined as exceeding desirable weight by
10% - 20%, or a BMI of 25 and 30
• Obesity occurs when a person is more than 20% above
desired weight, or with a BMI over 30
27
18.6: Vitamins
• Vitamins are organic compounds, other than carbohydrates,
lipids and proteins, that are essential for normal metabolic
processes
• Vitamins cannot be synthesized by body cells in adequate
amounts
• Vitamins are classified on the basis of solubility as either fatsoluble (vitamins A, D, E, and K) or water-soluble (the B
vitamins and vitamin C)
28
29
Fat-Soluble Vitamins
• The fat-soluble vitamins dissolve in fats and are influenced
by lipids
• Bile salts promote fat-soluble vitamin absorption
• They are fairly resistant to heat (not destroyed by cooking
and/or food processing)
• Includes vitamins A, D, E, and K
30
31
Water-Soluble Vitamins
• The water-soluble vitamins include the B vitamins and
vitamin C
• Cooking and food processing destroy them
• B vitamins (six of them) are several compounds essential for
normal cellular metabolism and known as the vitamin B
complex
32
33
18.7: Minerals
• Dietary minerals are inorganic elements that are essential in
human metabolism
• These are usually extracted from the soil by plants
• They are obtained by humans from plant foods or animals
that have eaten plants
• They are responsible for roughly 4% of body weight
34
Characteristics of Minerals
• Minerals are most concentrated in the bones and teeth
• They are typically incorporated into organic molecules
(phospholipids, hemoglobin and iodine in thyroxine)
• They compose parts of the structural materials of all cells
• Homeostatic mechanisms regulate the concentration of
minerals in body fluids
• Mineral toxicity can result from too much of a mineral or
from overexposure to industrial pollutants, household
chemicals, or certain drugs
35
Major Minerals
36
Trace Elements
• Trace elements (microminerals) are essential minerals found
in minute amounts, each makes up less than 0.005% of body
weight
• They include:
• Iron
• Manganese
• Copper
• Iodine
• Cobalt
• Zinc
• Fluorine
• Selenium
• Chromium
37
38
18.8: Healthy Eating
• An adequate diet provides sufficient energy (calories),
essential fatty acids, essential amino acids, vitamins, and
minerals to support optimal growth and to maintain and repair
body tissues
• Requirements vary with age, sex, growth rate, level of
physical activity and stress, and genetic and environmental
factors
• Dietary requirements such as recommended daily
allowances (RDA) are best to follow
• The U.S. Department of Agriculture’s Food Pyramid is
another tool to follow
• Nutritional information as well as ingredients are listed on
39
most grocery items for retail sale
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
(a) Activity
Activity is represented by the steps
and the person climbing them, as a
reminder of the importance of daily
physical activity.
Proportionality
Proportionality is shown by the
different widths of the food group
bands. The widths suggest how much
food a person should choose from
each group. The widths are just a
general guide, not exact proportions.
Moderation
Moderation is represented by the
narrowing of each food group from
bottom to top. The wider base
stands for foods with little or no
solid fats or added sugars. These
should be selected more often. The
narrower top area stands for foods
containing more added sugars and
solid fats. The more active you are,
these foods can fit into your diet.
MyPyramid.gov
GRAINS
VEGE TABLES
OILS
STEPS TO A HEALTHIER YOU
Personalization
Personalization is shown by the
person on the steps and the
slogan.
U.S. Department of Agriculture
Center for Nutrition Policy
and Promotion
April 2005 CNPP-16
Variety
Variety is symbolized by the 6 color
bands representing the 5 food groups
of the Pyramid and oils. This illustrates
that foods from all groups are needed
each day for good health.
FRUITS
Gradual Improvement
Gradual improvement is encouraged by
the slogan. It suggests that individuals
Can benefit from taking small steps to
improve their diet and lifestyle each day.
MEAT &
BEANS
MILK
USDA is an equal opportunity provider and employer.
(b)
(c)
Daily Beverage
Recommendations:
6 glasses
of water
Sweets
Olive
Oil
Fats
Protein/Dairy
Wine in
moderation
Carbohydrates
Meat
Monthly
Sweets
Eggs
Poultry
Fish
Cheese & Yogurt
Weekly
Fruits
Olive
Oil
Vegetables
Mayo Clinic Healthy Weight Pyramid
Meats
Sweets
Eggs and poultry
Fish and shell fish
or dairy
Vegetable oils
Whole grains
& potatoes
Fruits
Olive oil
Beans, legumes Vegetables
& nuts
Daily
Daily Physical Activity
Monthly
Weekly
The Mediterranean Diet Pyramid
Optional daily
Daily
Fruits, legumes,
nuts, seeds, vegetables
Rice, rice products,
noodles, breads, millet,
corn and other grains
(d)
Physical activity
The Asian Diet Pyramid
Sake, wine, beer,
other alcoholic
beverages and tea
40
Malnutrition
• Malnutrition is poor nutrition that results from a lack of
essential nutrients or failure to use them
• Undernutrition – deficiency of essential nutrients
• Overnutrition – excess of nutrient intake
• Malnutrition can be a result of:
• Primary malnutrition – malnutrition from diet alone
• Secondary malnutrition – adequate diet but
individual characteristics make the diet insufficient
41
Starvation
• A healthy human can survive 50-70 days without food
• Symptoms include low blood pressure, slow pulse, chills,
dry skin, hair loss, and poor immunity
• Common nutritional disorders include:
• Marasmus – lack of all nutrients
• Kwashiorkor – protein starvation
• Anorexia nervosa – eating disorder; self-starvation
• Bulimia – eating disorder; binge and purge cycle
42
18.9: Lifespan Changes
• Dietary requirements remain generally the same throughout
life
• BMR rises in early childhood and peaks in adolescence
• BMR declines in adulthood
• Change in nutrition often reflects the effects of medical
conditions and the social and economic circumstances
43
Important Points in Chapter 18:
Outcomes to be Assessed
18.1: Introduction
 Define nutrition, nutrients, and essential nutrients.
 Explain appetite control.
18.2-18.4: Carbohydrate - Proteins
 List the major sources of carbohydrates, lipids, and proteins.
 Describe how cells utilize carbohydrates, lipids, and proteins.
 Define nitrogen balance.
18.5: Energy Expenditures
 Explain how energy values of food are determined.
 Explain the factors that affect an individual’s energy requirements.
 Define energy balance.
44
Important Points in Chapter 18:
Outcomes to be Assessed
 Explain what is meant by desirable weight.
18.6: Vitamins
 List the fat-soluble and water-soluble vitamins and summarize the
general functions of each vitamin.
18.7: Minerals
 Distinguish between a vitamin and a mineral.
 List the major minerals and trace elements and summarize the general
functions of each.
18.8: Healthy Eating
 Describe an adequate diet.
 Distinguish between primary and secondary malnutrition.
45
Important Points in Chapter 18:
Outcomes to be Assessed
18.9: Lifespan Changes
 List the factors that may lead to inadequate nutrition later in life.
46