Nutrition 160-01; CRN # Fall-84002—Spring-14249
Page 1
Chapter 1 -- “An Overview of Nutrition,” by Whitney, E. N., and Rolfes, S. R., in “Understanding Nutrition” – any edition
Definitions

Nutrition
o
The science of foods and the nutrients and other substances they contain, and of their actions within the body – ingestion,
digestion, absorption, transport, metabolism, excretion
o
The social, economic, cultural, and psychological implications of food and eating

Foods
o
Products derived from plants or animals taken into the body to yield energy and nutrients for the maintenance of life and
the growth and repair of tissues

Diet
o
The foods and beverages a person eats and drinks
Food Choices

Personal preference (e.g., sugar/salt/fat)

Habit

Ethnic heritage/tradition

Social interactions (e.g., companionship)

Availability, convenience, economy

Positive and negative associations (e.g., hot dogs at ballgame, cake at birthday, veggies as a child)

Emotional comfort

Values (e.g., religious beliefs; imports; genetically modified)

Body weight and image

Nutrition (e.g., benefit health; functional food – plant sterol in margarine to lower cholesterol, or fortified juice)
[SUMMARY – Individual food selections don’t matter as much as balance of foods selected over time; think “nutrition” when making food
choices]
Definitions for “The Nutrients”

Lipids
o
Fats

Functional foods
o
Foods that contain physiologically active compounds that provide health benefits beyond their nutrient contributions

Energy
o
The capacity to do work; the energy in food is chemical energy; the body converts chemical energy into mechanical,
electrical, and heat energy

Energy-yielding nutrients
o
Carbohydrate, fat, protein (and alcohol)

Calories
o
Units by which energy is measured. Food energy is measured in kilocalories (1000 calories equal 1 kcal
o
One kcal is the amount of heat necessary to raise the temperature of 1 kg of water 1 degree celsius

Nutrients
o
Chemical substances obtained from food used in the body to provide energy to support growth, maintenance, and repair of
the body’s tissues, and to reduce risk of disease
The Nutrients

Composition of foods
o
Water (H2O), carbohydrates, lipids, proteins, vitamins, minerals, other

Composition of the body
o
Same as food

Chemical composition of nutrients
o
6 classes

Inorganic (no carbon)

Minerals (minerals)

Water (hydrogen, oxygen)

Organic (carbon containing)

Carbohydrates (carbon, hydrogen, oxygen)

Lipids (carbon, hydrogen, oxygen)

Proteins (carbon, hydrogen, oxygen, nitrogen; some include the mineral sulfur)

Vitamins (carbon, hydrogen, oxygen; some include nitrogen and minerals)
o
Macronutrients – Carbohydrate, fat, and protein due to large molecules
o
Micronutrients – Vitamins and minerals due to small molecules

Essential nutrients
o
Needed from outside the body because body cannot make in sufficient quantity
o
About 35-40 nutrients
o
Also called indispensible

Nonnutrients
o
Alcohols
o
Phytochemicals (plant-derived foods that have biological activity in the body
o
Pigments
o
Additives

Energy values for nutrients
Nutrition 160-01; CRN # Fall-84002—Spring-14249
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o
Carbohydrate – 4 kcal/g
o
Fat – 9 kcal/g
o
Protein – 4 kcal/g
o
(Alcohol – 7 kcal/g but is not considered a nutrient because it interferes with the body’s growth, maintenance, and repair)

Energy in the body
o
If energy need exceeds energy intake from food, a loss of weight is due to breakdown of body reserves first of fat then of
protein
o
If energy need is less than energy intake from food, a gain of weight is due to the storage of fat (food components are
broken down and rearranged into lipid)
o
Energy needs calculated on a daily basis, not individual meal; want to limit fat intake to 30 percent of kcal

Vitamins
o
Organic but provide no energy; facilitate release of energy from carbohydrate, fat, protein
o
13 total of significance

9 Water-soluble

Vitamin C

8 B vitamins: Thiamin, riboflavin, niacin, vitamins B6 and B12, folate, biotin, pantothenic acid

4 Fat-soluble

Vitamins A, D, E, and K
o
Susceptible to light, heat, and chemical agents

Minerals
o
Approximately 16 essential
o
Indestructible since not organic

Water
o
Essential
o
Naturaly carries many minerals
o
No energy derived from this nutrient
[SUMMARY – Six classes of nutrients: carbohydrates, fats, proteins, vitamins, minerals, water; energy measured in kcal with 4 from
carbohydrate, 9 from fat, 4 from protein, and 7 from alcohol]
The Science of Nutrition
o
Research Designs

Epidemiological studies

Relationship between what is eaten, health of the community, disease

Animal studies

Controlled conditions observed with/without nutrient and estimate the impact on humans

Case-control studies

Comparison of people who do/do not have a given condition, closely matching them in age, gender, and
other variables so that differences in other factors will stand out

Human intervention (or clinical) trials

People adopt a new behavior and effectiveness determined
o
Research Validity
o
Was there similarity between the control group and the experimental group?
o
Was the sample size large enough to rule out chance variation?
o
Was a placebo effectively administered (blind)?
o
Was the experiment double blind?
[SUMMARY – Peer review, a process by which a panel of scientists evaluate the study to confirm that it followed standard scientific methods is
critical for concluding that a nutrient has an effect; conclusions can be drawn scientifically or by “rumor”]
Definitions for “Dietary Reference Intakes”
o
DRI
o
Set of values for the dietary intake of healthy people in the U.S. and Canada

Estimated average requirements

Recommended dietary allowances

Adequate intakes

Tolerable upper intake levels

Requirement
o
Lowest continuing intake of a nutrient that will maintain a specified criterion of adequacy

Estimated average requirement
o
The amount of a nutrient that will maintain a specific biochemical or physiological function in half the people of a
given age and gender group

Recommended dietary allowance (RDA)
o
The average daily amount of a nutrient considered adequate to meet the known needs of practically all healthy
people; a goal for dietary intake by individuals

Deficient
o
The amount of a nutrient below which almost all healthy people can be expected, over time, to experience deficiency
symptoms

Registered dietician
o
A college-educated food and nutrition specialist who is qualified to evaluate people’s nutritional health and needs
Nutrition 160-01; CRN # Fall-84002—Spring-14249
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Adequate intake (AI)
o
The average amount of a nutrient that appears sufficient to maintain a specified criterion; a value used as a guide for
nutrient intake when an RDA cannot be determined

Tolerable upper intake level
o
The maximum amount of a nutrient that appears safe for most healthy people and beyond which there is an increased
risk of adverse health effects
Dietary Reference Intakes – Using Nutrient Recommendations
1. These apply to healthy people
2. There is a generous margin of safety
3. Can be met through a varied diet
4. They apply to average daily intakes
5. Each of the 4 DRI categories serve a unique purpose:

Estimated Average Requirements

Recommended Dietary Allowances

Adequate Intake

Tolerable Upper Intake Level
[SUMMARY - The 4 DRI categories can be used to plan a healthy diet for healthy people]
Definitions for “Nutrition Assessment”
o
Malnutrition
o
Any condition caused by excess or deficient food energy or nutrient intake, or by an imbalance of nutrients
o
Undernutrition
o
Deficient energy or nutrients
o
Overnutrition
o
Excess energy or nutrients
o
Nutrition assessment
o
A comprehensive evaluation of a person’s nutrition status, completed by a registered dietitian, using health,
socioeconomic, drug, and diet history, anthropometric measurements, physical examinations, and laboratory tests
o
Anthropometric
o
Relating to measurement of the physical characteristics of the human body, such as height and weight
o
Primary deficiency
o
A nutrient deficiency caused by inadequate dietary intake of a nutrient
o
Secondary deficiency
o
A nutrient deficiency caused by something other than an inadequate intake such as a disease condition that reduces
absorption, accelerates use, hastens excretion, or destroys the nutrient
o
Overt
o
Out in the open and easy to observe
o
Covert
o
Hidden from observation
o
Food consumption survey
o
A survey hat measures the amounts and kinds of foods people consume (using diet history), estimates the nutrient intakes,
and compares them with a standard
o
Nutrition status survey
o
A survey that evaluates people’s nutrition status using diet histories, anthropometric measures, physical examinations, and
laboratory tests
o
Healthy people
o
A national public health initiative via HHS that identifies the most significant preventable threats to health and focuses
efforts towards eliminating them
Nutrition Assessment of Individuals
o
Historical information (diet history and health history)
o
Anthropometric data
o
Physical exam
o
Laboratory tests
Nutrition Assessment of Populations
o
National nutrition surveys (food consumption survey; nutrition status survey; national health goals – healthy people)
o
Leading causes of death in the U.S.
o
Heart disease – 31.4 (% of total deaths)
o
Cancers – 23.3
o
Strokes – 6.9
o
Chronic obstructive lung disease – 4.7
o
Accidents – 4.1
o
Pneumonia and influenza – 3.7
o
Diabetes mellitus – 2.7
o
Suicide – 1.3
o
Kidney disease – 1.1
o
Chronic liver disease – 1.1
o
Healthy People 2010 Nutrition and Overweight Objectives
o
Increase proportion of adults and children at a healthy weight
o
Reduce the proportion of adults and children who are obese
o
Increase daily serving of fruit to at least two servings
Nutrition 160-01; CRN # Fall-84002—Spring-14249
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Increase daily serving of vegetables to at least three servings, with one being dark green or orange vegetables
o
Increase daily serving of grain to at least six servings, with at least three being whole grains
o
Increase proportion of persons who consume less than 10 % of kcal from saturated fat
o
Increase proportion of persons who consume no more than 30 % of kcal from total fat
o
Increase proportion of persons who consume 2400 mg or less of sodium
o
Increase proportion of persons who meet daily recommendations for calcium
o
Reduce iron deficiency for females, especially those of child-bearing age and pregnant women
o
Reduce anemia among low-income pregnant females in their third trimester
o
Increase proportion of children whose intake of meals and snacks at school contributes to good overall dietary quality
o
Increase the proportion of worksites that offer nutrition or weight management classes
o
Increase the proportion of physician office visits by patients with cardiovascular disease, diabetes, or hyperlipidemia
o
Increase food security and reduce hunger
[SUMMARY – 4 tools are used to assess nutrition status; nutrition-related causes for death rank among the highest causes; Healthy People 2010
focuses on preventable threats to health]
Definitions for “Diet and Health”
o
Chronic diseases
o
Long-duration degenerative diseases characterized by deterioration of the body organs (e.g., heart disease, cancer, and
diabetes)
o
Risk factor
o
A condition or behavior associated with an elevated frequency of a disease but not proved to be causal (e.g., overweight,
cigarette smoking, alcohol abuse, high blood pressure, high blood cholesterol, high-fat diet, physical inactivity)
Nutrition 160-01; CRN # Fall-84002—Spring-14249
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Chapter 2 -- “Planning a Healthy Diet,” by Whitney, E. N., and Rolfes, S. R., in “Understanding Nutrition” -- any edition
Definitions in “Planning a Healthy Diet”

ABC’s of Good Health
o
Aim for fitness
o
Build a healthy base
o
Choose sensibly

Adequacy (dietary)
o
Providing all the essential nutrients, fiber, and energy in amounts sufficient to maintain health

Balance (dietary)
o
Providing foods of a number of types in proportion to each other, such that foods rich in some nutrients do not crowd out of
the diet foods that are rich in other nutrients

Empty-kcal foods
o
Foods that contribute energy but lack protein, vitamins, and minerals

Enriched
o
Foods that have had some nutrients added back

Exchange lists
o
Diet-planning tools that organize foods by their proportions of carbohydrate, fat, and protein. Foods on any single list can
be used interchangeably.

Food group plans
o
Diet-planning tools that sort foods of similar origin and nutrient content into groups and then specify that people should eat
certain numbers of servings from each group

Fortified
o
The addition to a food of nutrients that were either not originally present or present in insignificant amounts.

Health claims
o
Statements that characterize the relationship between a nutrient in a food and a disease (e.g., calcium and osteoporosis; oats
and cholesterol)

Legumes
o
Plants of the bean and pea family, rich in high-quality protein compared with other plant-derived foods (includes the
following: Black beans, black-eyed peas, garbanzo beans, great northern beans, kidney beans, lentils, navy beans, peanuts,
pinto beans, soybeans, split peas)

Kcal (energy) control
o
Management of food energy intake

Miscellaneous foods
o
Foods that do not fit into any of the major food groups, which should be used sparingly (e.g., fats, oils, sweets, including
salad dressing, jam, alcoholic beverage)

Moderation (dietary)
o
Providing enough but not too much of a substance

Nutrient density
o
A measure of the nutrients a food provides relative to the energy it provides. The more nutrients and the fewer kcal, the
higher the nutrient density

Refined food
o
A food that has lost many nutrients during processing

Variety (dietary)
o
Eating a wide selection of foods within and among the major food groups

Whole-grain
o
Grain-type foods that may be rich in all nutrients found in the original grain
Diet Planning Principles

Six diet-planning principles
1. Adequacy
2. Balance
3. Kcal control
4. Nutrient density
5. Moderation
6. Variety

To calculate nutrient density, divide quantity of nutrient by total energy (e.g., 301 mg Ca/86 kcal = 3.5 mg per kcal)

Dietary Guidelines for Americans (i.e., “What should an individual eat to stay healthy?”
o
Aim for a healthy weight
o
Be physically active each day
o
Let the Pyramid guide your food choices (i.e., the graphic depiction of the Daily Food Guide)
o
Choose a variety of grains daily, especially whole grains
o
Choose a variety of fruits and vegetables daily
o
Keep food safe
o
Choose a diet that is low in saturated fat and cholesterol and moderate in total fat
o
Choose beverages and foods that limit your intake of sugars
o
Choose and prepare foods with less salt
o
If you drink alcoholic beverages, do so in moderation

Choose a diet that provides:
o
</= 30 kcal from fat
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o
15-20 % kcal from protein
o
55-60 % kcal from carbohydrates
Diet Planning Guides

Tools for diet planning include:
o
Food Group Plans

Daily Food Guide – Assigns foods to five major groups, sorted primarily by protein, vitamin, and mineral
content

Bread (especially whole grain): 6-11 daily servings

Vegetable: 3-5 daily servings

Fruit: 2-4 daily servings

Milk (preferably nonfat or low fat): 2 servings (more if pregnant and/or young)

Meat or alternates (preferably lean or low fat): 2-3 servings

Vegetarian Food Guide – Mainly plant foods (grains, vegetables, legumes, fruits, seeds, nuts)
o
Exchange Lists

Assigns foods to three major groups, sorted primarily by the proportion of carbohydrate, fat, and protein

Focus is on portion sizes

Carbohydrate group includes:

Starch (cereal, grain, pasta, bread, cracker, snack, starchy vegetable, dried bean, pea, lentil)

Fruit

Milk

Other carbohydrate (e.g., dessert)

Vegetable

Portion size (Any food on a given list provides roughly the same amount of carbohydrate, fat, and protein and,
therefore, total kcal):

Meat – 3 ounces = size of deck of cards

Vegetable – 1 cup = size of your fist

Fruit – small = size of tennis ball
From Guidelines to Groceries

Grain enrichment nutrients:
o
Iron
o
Thiamin
o
Riboflavin
o
Niacin
o
Folate
Food Labels

“Nutrition Facts” Panel has serving size and servings per container, plus:
o
Total food energy (kcal)
o
Food energy from fat (kcal)
o
Total fat (grams)
o
Saturated fat (grams)
o
Cholesterol (milligrams)
o
Sodium (milligrams)
o
Total carbohydrate, including starch, sugar, and fiber (grams)
o
Dietary fiber (grams)
o
Sugars (grams)
o
Protein (grams)
o
Vitamin A
o
Vitamin C
o
Iron
o
Calcium

Daily Values
o
Reflect dietary recommendations for nutrients and dietary components that have important relationships with health.
o
It compares key nutrients in a serving of food with the daily goals of a person consuming 2000 kcals.

A 2000-kcal diet is considered appropriate for moderately active females and sedentary males

A 2500-kcal diet is considered appropriate for men and active women
Nutrition 160-01; CRN # Fall-84002—Spring-14249
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Chapter 3 -- “Digestion, Absorption, and Transport,” by Whitney, E. N., and Rolfes, S. R., in “Understanding Nutrition” -- any edition
DIGESTION
Anatomy of the Digestive Tract

Water is critical for maintaining the right consistency to move the digestive tract contents through the system

The walls of the digestive tract are made of carbohydrate, fat, and protein and must be protected against digestive juices

Motility, involving peristalsis, causes food to move through the GI tract

The process of ingestion to elimination involves the following: Mastication in the mouth →swallowing the food forming a bolus that
passes through the pharynx→epiglottis→esophagus→stomach for grinding and mixing forming a chyme→small intestion
(duodenum→jejunum→ileum) with secretions from the gallbladder and pancreas to further digest the chyme→large intestine (colon -ascending colon, transverse colon, descending colon) where it reabsorbs water and minerals→waste (fiber, bacteria, and unabsorbed
nutrients) passed along to the rectum
The Muscular Action of Digestion

When chime is present, peristalsis occurs 3 times per minute in the stomach; 10 times per minute in then small intestine

When GI tract is empty, periodic peristalsis bursts occur

Stomach has the thickest walls and the strongest muscles of all the GI tract organs, consisting of three layers of circular, longitudinal,
and diagonal muscles

In the stomach, when the chime is liquefied by the churning and mixing with digestive secretions, the pyloric sphincter opens about
three times a minute and allows the chyme through into the small intestine
The Secretions of Digestion

Five organs produce secretions to breakdown food into nutrients:
1. Salivary glands
2. Stomach
3. Pancreas
4. Liver (via the gallbladder)
5. Small intestine

Gastric juice
o
Water
o
Enzymes
o
Hydrochloric acid

Pancreatic juice
o
Ducts leading into duodenum secrete digestive juices
o
Contains sodium bicarbonate
o
Neutralizes chyme

Bile
o
From the liver which is stored and concentrated in the gallbladder
o
Triggered by fat in the chyme
o
Not an enzyme, but an emulsifier that brings fats into suspension in water so that enzymes can break them down
The Final Stage

Carbohydrates, fat, and protein must be disassembled for absorption, but minerals and vitamins do not need to be disassembled

Undigested residues, such as some fibers, are not absorbed but serve as the major component of stools
Absorption

The small intestine is the organ in which the majority of nutrients are absorbed

Blood washes the underside of the small intestine and transports them to the liver and other parts of the body
Anatomy of the Absorptive System

Inner surface of the small intestine is lined with villi that are comprised of microvilli with crypts in the crevices between the villi. The
microvilli trap nutrient particles and transport them to the cells; the crypts are glands that secreate intestinal juices into the small
intestine
A Closer Look at the Intestinal Cells

The cells of the villi recognize and select the nutrients the body needs and regulate their absorption

The cells of successive portions of the intestinal tract are specialized to absorb different nutrients

Nutrients pass through the cells of the villi and enter either the blood (if they are soluble in water or smaller fat fragments) or the
lymph (if they are fat soluble)
THE CIRCULATORY SYSTEMS
The Vascular System

The vascular, or blood circulatory, system circulates throughout the body, with the heart as the pump

Blood is carried to the digestive system by way of an artery which branches into capillaries to reach every cell

Blood leaving the digestive system goes by way of a vein, which branches into capillaries to reach every cell, to the liver and then to
the heart

The liver is the first to receive the materials absorbed from the GI tract and is the body’s major metabolic organ
The Lymphatic System

The lymphatic system is a one-way route for fluid from the digestive system to enter the vascular system, bypassing the liver at first

Material in the lymphatic system move by muscle contraction elsewhere in the body, and are not moved by a pump
REGULATION OF DIGESTION AND ABSORPTION
Gastrointestinal Hormones and Nerve Pathways

Factors influencing GI function
o
Physical immaturity
o
Aging
o
Illness
Nutrition 160-01; CRN # Fall-84002—Spring-14249
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o
Nutrition
Two systems coordinate all the digestive and absorptive processes
1. Hormonal (endocrine) system
2. Nervous system
The stomach maintains a pH of 1.5 to 1.7
Definitions (Chapters 3 and 4)

Absorption
o
The passage of nutrients from the gastrointestinal (GI) tract into either the blood or the lymph

Bile
o
An emulsifier from the liver that prepares fat and oil for digestion; stored and concentrated in the gallbladder and secreted
into the small intestine

Bolus
o
Food that has been swallowed

Colon
o
The lower portion of the intestine that completes the digestive process, also known as the large intestine

Complex carbohydrate
o
Starch and fiber consisting of polysacchariedes

Diabetes
o
A disorder of carbohydrate metabolism resulting from inadequate or ineffective insulin

Digestion
o
The process by which food is broken down into absorbable units

Disaccharide
o
Pairs of monosaccharides linked together

Duodenum
o
The top portion of the small intestine

Enzyme
o
A protein that facilitates a chemical reaction (making, breaking, changing the arrangement of, or exchanging parts of a
molecule)

Epiglottis
o
Cartilage in the throat that guards the entrance to the trachea and prevents fluid or food from entering it when a person
swallows

Epinephrine
o
A hormone of the adrenal gland that modulates the stress response (also known as adrenaline)

Fiber
o
Non-starch polysaccharide not digested by human digestive enzymes (e.g., cellulose, pectins)
o
Form the structural parts of plants

Fructose
o
A monosaccharide
o
Commonly known as fruit sugar
o
The sweetest of the sugars

Gallbladder
o
The organ that stores and concentrates bile; when it receives a signal that fat is present in the duodenum, it contracts and
squirts bile through the bile duct into the duodenum

Galactose
o
A monosaccharide
o
Commonly known as milk sugar

Gastrointestinal (GI) tract
o
The digestive tract, which includes the stomach and intestines
o
A flexible muscular tube

Gastrin
o
A hormone secreted by cells in the stomach wall that cause the glands of the stomach to secrete gastric acid

Glucagon
o
A hormone secreted by the pancreas in response to low blood sugar (glucose) causing stored glucose to be released

Glucose
o
A monosaccharide
o
Commonly known as blood sugar

Glycemic effect
o
A method used to classify foods according to their potential for raising blood glucose

Glycogen
o
An animal polysaccharide
o
Manufactured and stored in the liver and muscles as a storage form of glucose

Hydrochloric acid
o
The acidic component of gastric juice with a pH below 2 and stronger than vinegar

Hypoglycemia
o
An abnormally low blood glucose concentration

Ileum
o
The last segment of the small intestine
Nutrition 160-01; CRN # Fall-84002—Spring-14249
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
Insulin
o
Jejunum
o
Ketosis
o
Page 9
A hormone secreted by the pancreas in response to increased blood glucose levels; its primary role is to transport glucose
from the blood into the muscles and fat cells
The first two-fifths of the small intestine beyond the duodenum
High concentrations of ketone bodies in the blood and urine as a consequence of inadequate carbohydrate in the diet and
the breaking down of fat in the body
Lactase
o
An enzyme that breaks down lactose

Lactose intolerance
o
A condition that results from inability to digest the milk sugar lactose that is characterized by bloating, gas, abdominal
discomfort, and diarrhea.

Lumen
o
The inner space within the GI tract, which is continuous from the mouth through the esophagus, stomach, small intestine,
large intestine, and rectum to the anus.

Mastication
o
The process of chewing, breaking down large pieces of food into smaller pieces

Monosaccharide
o
Carbohydrates that consist of a single ring (fructose, galactose, glucose)

Pancreas
o
A gland that secretes digestive enzymes and juices into the duodenum

Peristalsis
o
Wavelike muscular contractions of the GI tract that push its contents along

Pharynx
o
A short tube that is shared by both the digestive system and the respiration system

Polysaccharide
o
Compound composed of many monosaccharides linked together

Simple carbohydrate
o
Sugar consisting of monosaccharides and disaccharides

Small intestine
o
A 10-foot length of small-diameter of intestine that is the major site of digestion of food and absorption of nutrients; its
segments are the duodenum, jejunum, and ileum

Sodium bicarbonate
o
Alkaline (basic) substance contained in the pancreatic juice

Starch
o
Plant polysaccharides composed of glucose
o
Grains are the richest food source

Stomach
o
A muscular, elastic saclike portion of the digestive tract that grinds and churns the bolus, mixing it with acid and enzymes
to form chyme

Sucrose
o
A disaccharide composed of glucose and fructose
o
Table sugar

Type 1 Diabetes
o
Less common type of diabetes in which the person does not produce insulin (known as insulin-dependent diabetes mellitus
(IDDM) or juvenile-onset diabetes; generally thought to be a genetic defect

Type 2 Diabetes
Most common type of diabetes in which the fat cells resist insulin (known as non-insulin-dependent diabetes mellitus (NIDDM) or adult-onset
diabetes; generally thought to be a consequence of obesity
Nutrition 160-01; CRN # Fall-84002—Spring-14249
Page 10
Chapter 4 -- “The Carbohydrates: Sugars, Starches, and Fibers,” by Whitney, E. N., and Rolfes, S. R., in “Understanding Nutrition” -- any
edition
THE CHEMIST’S VIEWS OF CARBOHYDRATES

The brain uses glucose to provide energy for learning

Half of all the energy needed for sports is provided by glycogen, while the other half is provided by fat
DIGESTION AND ABSORPTION OF CARBOHYDRATES
The Processes of Digestion and Absorption

The goal of digestion and absorption of sugar and starch is to dismantle them into small molecules, primarily glucose

The small intestine performances most of the work of carbohydrate digestion due to the lack of specific enzymes in the stomach

Within one to four hours after a meal, all of the sugars and most of the starches have been digested

For the most part, glucose absorption takes place in the small intestine

In digestion and absorption of carbohydrates, the body breaks down starches as follows:
starches→disaccharides→monosaccharides→glucose
Lactose Intolerance

Lactase, an enzymen, is at its highest level in the body after birth but declines during childhood and adolescences to about 5-10
percent of the activity at birth

Milk is a major source of several nutrients:
o
Calcium
o
Riboflavin (a B vitamin)
o
Vitamin D
GLUCOSE IN THE BODY
A Preview of Carbohydrate Metabolism

The liver stores one-third of the body’s total glycogen and releases glucose as needed

The muscles of the body store the other two-thirds of the body’s total glycogen

Glycogen is used as the short-term energy supply (up to a few hours of exercise); fat is used for long-term energy needs (up to days)

Carbohydrate is known as “protein-sparing” which means that injestion of dietary carbohydrate prevents the dismantling of protein
(from muscle, for example) to supply the body’s glucose

Glucose is the only energy source for the brain

Carbohydrate is not as easily stored as body fat as is dietary fat
The Constancy of Blood Glucose

Blood glucose levels are regulated by two hormones:
o
Insulin
o
Glucagon

Too little glucose causes dizziness and weakness; too much glucose causes fatigue

Special cells in the pancreas secrete insulin into the blood after a meal by ushering blood glucose into cells for use or storage as
glycogen

Other special cells in the pancreas secrete glucagons into the blood when blood glucose falls, causing the liver to dismantle its
glycogen stores and release glucose

Epinephrine (also known as adrenaline) is a hormone known as the “fight-or-flight” hormone that causes increased energy
availability in times of stress

Type 1 Diabetes
o
Less common type (e.g., genetic)
o
The pancreas fails to make insulin

Type 2 Diabetes
o
More common type
o
Generally a consequence of obesity

Hypoglycemia
o
Blood glucose levels drop dramatically, producing symptoms that mimic an anxiety attack (weakness, rapid heartbeat,
sweating, anxiety, hunger, and trembling)
o
People with hypoglycemia must regularly eat small portions of carbohydrate throughout the day

Low glycemic effect
o
Slow absorption, a modest rise in blood glucose, and a smooth return to normal – desirable

High glycemic effect
o
Fast absorption, a surge in blood glucose, and an overreaction that plunges glucose below normal – undesirable
Nutrition 160-01; CRN # Fall-84002—Spring-14249
Page 11
Chapter 5 -- “The Lipids: Triglycerides, Phospholipids, and Sterols,” by Whitney, E. N., and Rolfes, S. R., in “Understanding Nutrition” -any edition
The Chemist’s View of Fatty Acids and Triglycerides

Every triglyceride contains one molecule of glycerol and three fatty acids
Fatty Acids

Most fatty acids contain an even number of carbons in their chain, up to 24 carbons in length

Polyunsaturated fatty acids are identified by the position of the double bond (=) nearest to the methyl (CH3) group, which is described
by an omega number (e.g., an omega-3 fatty acid has the methyl group three carbons away from the double bond). [On the exam, you
will need to identify which structure is an omega-3 compound; practice by identifying which of the following two structures is the
omega-3 fatty acid:

1 -- CH3-CH2-CH1=CH1-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-COOH

2 -- CH3-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH1=CH1-CH2-COOH
Degree of Unsaturation Revisited

Know Table 5-1 (the chart with the four major 18-carbon fatty acids)
o
Stearic acid has no double bonds, is saturated, and is in most animal fats
o
Oleic acid has 1 double bond, is monounsaturated, and is in olive and canola oils
o
Linoleic acid has 2 double bonds, is polyunsaturated, and is in sunflower, safflower, and corn oils
o
Linolenic acid has 3 double bonds, is polyunsaturated, and is in soybean oil

The degree of unsaturation influences the firmness of fats at room temperature. Generally, saturated fats are solid at room temperature
(e.g., lard) and polyunsaturated fats are liquid at room temperature (e.g., vegetable oil)
Stability

Saturation influences stability. All fats can become rancid when exposed to oxygen. Polyunsaturated fats (e.g., vegetable oil) spoil
most readily due to high number of double bonds.
Trans-Fatty Acids

Special fatty acids that are produced upon hydrogenation making the fat more like saturated fats and having a negative impact on
public health, specifically regarding heart disease
The Chemist’s View of Phospholipids and Sterols
Phospholipids

The best known phospholipid is lecithin because the fatty acids are soluble in fat and the phosphate group (with choline) is soluble in
water and serves as an emulsifier such as in mayonnaise.

The liver makes from scratch all the lecithin that the cell membranes need.
Sterols

Compounds with a multi-ring structure, with the most famous sterol being cholesterol

Foods of plant and animal original contain sterols, but only those from animals (beef, pork, poultry, fish, eggs, and dairy) contain
cholesterol

Vitally important body compounds contain sterols: bile acids, sex hormones (e.g., testosterone), adrenal hormones, cholesterol, and
vitamin D

The liver makes cholesterol for the body’s needs, although cholesterol also is consumed in the diet
Digestion, Absorption, and Transport of Lipids

The goal of fat digestion is to dismantle triglycerides into small molecules that the body can absorb and use – mainly monoglycerides,
fatty acids, and glycerol

Fats are hydrophobic (they don’t mix well with water) but enzymes that digest fat are hydrophilic (they mix well with water).
Therefore, the digestive system is devised in a way to mix the enzymes with the fats

Although fat is broken down beginning with the mixture of saliva and its enzymes and the churning of the stomach, fat molecules
primarily are digested in the small intestine

Fat in the small intestine triggers release of the hormone cholecystokinin (CCK), which signals the gallbladder to release bile (the liver
manufacturers bile acids from cholesterol, and the gallbladder stores the bile until needed)

Bile acts as an emulsifier (because one end is hydrophobic while the other end is hydrophilic), causing fat to draw into the watery
fluids with the lipase enzymes

Blood cholesterol can be lowered due to the excretion of cholesterol that is trapped in soluble fiber (e.g., oat-containing food)
Lipid Absorption

Once fats are dismantled into smaller molecules (e.g., short- and medium-chain fatty acids, and glycerol), these molecules diffuse into
the intestinal cells and are directly absorbed into the bloodstream. For the larger molecules (e.g., monoglycerides and long-chain fatty
acids), they merge into spherical complexes called micelles. The micelles transport to the intestinal cells and are reassembled into
new triglycerides. The new triglycerides are packed into transport vehicles called chylomicrons that are released into the lymphatic
system where they enter the blood system at the thoracic duct near the heart

There are four main types of transport vehicles – as a group they are called lipoproteins -- for these larger molecules: chylomicrons;
very-low-density lipoprotein (VLDL); low-density-lipoprotein (LDL); and high-density-lipoprotein (HDL)

The blood cholesterol linked to heart disease is LDL cholesterol and is referred to as “bad” cholesterol; HDL is referred to as “good”
cholesterol because it represents the cholesterol fragment that is carrying cholesterol back to the liver to be dismantled and not for use
within the body

Chylomicrons carry all classes of lipids (triglycerides, phospholipids, and cholesterol) but are composed primarily of triglycerides;
VLDL are smaller than chylomicrons and carry about half triglycerides; LDL are smaller than VLDL and are composed primarily of
cholesterol; HDL are smaller than LDL and are composed primarily of protein

A public health goal is to improve the ratio of HDL to LDL in the body in order to have more HDL (“healthy”) and less LDL (less
healthy) cholesterol. This ratio can be improved by: weight control, physical activity, and a diet that has higher unsaturated fatty
acids than saturated fatty acids and increased soluble fibers
Roles of Triglycerides
Nutrition 160-01; CRN # Fall-84002—Spring-14249

Page 12
Fat is “protein sparing” because fat combines with glucose fragments during energy metabolism and spares body protein from being
used so that the protein can be stored for later use

Fat helps insulate the body, serves as a shock absorber around vital organs, and provides energy to the body (providing more than
twice the energy as protein or carbohydrate)
Essential Fatty Acids

The body can make all but two fatty acids: linoleic and lenolenic. There are essential because they must be consumed in the diet

The omega-three fatty acids that are important for disease prevention (e.g., heat, hypertension, arthritis, cancer) can be derived from
dietary linolenic acid which is an omega-three fatty acid. Dietary sources for omega-three fatty acids include: shellfish; some fish
(including, salmon, lake trout, and tuna); walnuts, and soybeans. Omega-three fatty acids make eicosanoids that help regulate blood
pressure, blood clot formation, and immune responses to injury and infection
A Preview of Lipid Metabolism

Adipose tissue stores fat, in the form of triglycerides, in the body
Using Fat for Energy

When energy is needed, triglycerides within the fat cells are dismantled and the glycerol and fatty acids are released into the
bloodstream. Not all energy can come from triglycerides since the brain needs glucose. Starvation can result in death even if fat
reserves are not depleted
Benefits from Monounsaturated Fats

Olive oil and canola oil, which are rich in monounsaturated fatty acids, are part of the “Mediterranean” diet and are believed to lower
blood LDL cholesterol levels even with a high-fat diet
Recommended Intakes of Fat

Saturated fat increases the risk of heart disease

It is recommended that the following be adhered to in the diet: reduce total fat intake to 30 percent or less of energy intake; reduce
saturated fat intake to less than 10 percent of energy intake; and reduce cholesterol intake to less than 300 milligrams daily