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Chapter 5
Choosing a Nutritious Diet
Learning Objectives
1. List several factors that influence dietary choices.
2. Describe the dietary guidelines proposed by the U.S. government and health organizations.
3. Describe the Food Guide Pyramid and its recommendations.
4. Explain how to use the MyPyramid Web site.
5. Describe the ingredients and nutrition facts labels on manufactured foods.
6. Describe the three functions of food.
7. List the three functions of biological energy.
8. List the seven components of food, and identify common foods that contain each component.
9. Define and distinguish between dietary supplements used as food and as drugs.
10. Describe the three kinds of vegetarian diets and several reasons for vegetarianism.
Key Terms
Amino acids (103)
Anemia (101)
Antioxidants (111)
Artificial fat (109)
Basal metabolic rate (BMR) (101)
Basal metabolism (101)
Calorie (101)
Carbohydrates (105)
Cellulose (107)
Cholesterol (107)
Complex carbohydrates (105)
Deoxyribonucleic acid (DNA) (105)
Dietary supplements (113)
Essential amino acids (103)
Essential nutrients (99)
Fat-soluble vitamins (109)
Fatty acids (107)
Fiber (105)
Food guide pyramid (93)
Fructose (105)
Functional food (111)
Galactose (105)
Gamma irradiation (117)
Glucose (105)
Glycogen (107)
Goiter (101)
Hemicellulose (107)
Homocysteine (111)
Ingredients label (95)
Insoluble fiber (107)
Kilocalorie (101)
Lactase (105)
Lacto-ovo-vegetarian (120)
Lactose (105)
Lacto-vegetarian (120)
Lecithin (107)
Linoleic acid (107)
Lipids (107)
Metabolism (101)
Minerals (111)
Monounsaturated fatty acid (107)
MyPyramid (93)
Nutraceutical (113)
Nitrates (103)
Nitrites (103)
Nonessential amino acids (103)
Nutrition facts label (95)
Nutritional calorie (101)
Percent daily value (99)
Phytochemicals (113)
Polyunsaturated fatty acid (107)
Protein (102)
Reactive hypoglycemia (120)
Recommended [daily] dietary allowances (RDA) (101)
Saturated fat (107)
Simple sugars (105)
Soluble fiber (107)
Starch (105)
Sucrose (105)
Sulfites (115)
Tartrazine (115)
Trans-fatty acid (109)
Vegan (119)
Vegetarian (119)
Vitamins (109)
Water-soluble vitamins (109)
Chapter Summary
In the United States, there are thousands of food items available. However, the U.S. food
industry, while efficient, offers many foods that can be unhealthy. The American diet contains
too much saturated fat and trans-fat, sugar, refined carbohydrates, and salt. These substances are
prevalent in fast foods, snack foods, packaged pastries, manufactured and restaurant foods, and
sodas. Poor nutrition increases the risk of heart disease, high blood pressure, some cancers, type
2 diabetes, and obesity. Thus, for most of us, good nutrition is a matter of informed choice.
To encourage and promote healthy dietary choices, the U.S. government, the World Health
Organization, the American Heart Association, and the American Cancer Society provide
guidelines for good nutrition based on the latest scientific evidence. The U.S. Departments of
Agriculture and Health and Human Services produced guidelines to help prevent diseases that
may result from poor nutrition, such as heart disease and cancer. In addition, the U.S.
government requires that all manufactured foods carry an ingredients label and a nutrition facts
label.
The U.S. Department of Agriculture developed the Food Guide Pyramid (FGP) to help people
plan a healthy diet. The FGP emphasizes the consumption of whole grains, fruits, and vegetables,
while limiting consumption of meats, whole-fat diary, and fatty, sugary snacks and sweets.
The Healthy Eating Pyramid, a proposed improvement on the FGP, emphasizes exercise and the
consumption of polyunsaturated fats, fruits, and vegetables rather than refined grain products,
meats, and sweets.
The ingredients label on a food product lists the components of the product in descending order
by weight. The nutrition facts label provides information on the amounts of certain nutrients in a
food product.
Food has three functions: to provide chemical constituents of the body; to provide energy; and to
provide pleasure. To be healthy and well, people must obtain approximately 40 essential
nutrients in the proper amounts and proportions from food. The 40 essential nutrients include the
eight amino acids, linoleic acid, water, and several kinds of vitamins and minerals. Food is
comprised of seven components: protein, carbohydrates, lipids (fats), water, vitamins, minerals,
and phytochemicals.
Dietary supplements are unregulated substances that are used to augment the nutritional
adequacy of the diet and drugs to heal or prevent illness.
Lecture Outline
Choosing a Nutritious Diet
•
For most Americans, good nutrition is a matter of informed choice.
•
Marketing and advertising are major influences on food consumption patterns.
•
The current American diet consists of too much saturated and trans-fat, refined
carbohydrate and sugar, and salt.
Dietary Guidelines for Eating Right
•
The U.S. food industry is a massive conglomerate of people who are mostly trying to
make a profit.
•
Because of this, there are many decisions made about our food that lean towards
improving profit rather than improving the health of the American public.
•
The U.S. government, as well as many other organizations, have developed guidelines for
good nutrition to educate the public and encourage good eating habits.
•
For example, the American Heart Association and American Cancer Society have
developed the following guidelines.
•
The USDA also gives guidelines that are updated every few years.
•
Some of the information in these guidelines varies slightly depending on the focus of the
guidelines, but they are all good guidelines.
•
The USDA’s focus is to promote wellness and decrease illness that results from poor
nutrition.
•
Heart disease, cancer, type 2 diabetes, GI diseases, blood pressure, and tooth decay are all
affected by what we eat.
•
Influences on Dietary Choices
– Family
– Ethnic and religious heritage
– Cultural eating patterns
– Social factors
– Time limitations on thoughtful food shopping and meal preparation
– Stress, which encourages consumption of fat, sugar, and salt (comfort foods)
– Eating in a cafeteria
Food Guide Pyramids
•
MyPyramid (www.MyPyramid.com) was released in 2005 and is designed to be a flexible
online tool.
•
It is different than what was recommended a few years ago and is much more specific to
the needs of people who are different sizes.
•
It encourages
– Variety
– Moderation
– Proportions
– Physical activity
– Gradual improvements
– Personalization
•
DASH Plan—Dietary Approaches to Stop Hypertension
– This is a plan set up by the U.S. Department of Health and Human Services to
address hypertension.
– Though not in the form of a pyramid, this is another way individuals can look at
how they are eating.
•
Healthy Eating Pyramid
– Nutritionists at Harvard wanted to address the deficiencies in the U.S.
government’s food pyramids.
– They recommend
•
Daily exercise to control weight and to maintain physical and mental
health, irrespective of weight control.
•
Replace saturated fat, cholesterol, and trans-fats in manufactured and
restaurant foods with polyunsaturated fats found in canola, olive,
sunflower, and corn oils.
•
Replace refined grains with whole grains.
•
Consume more than 5-a-day servings of a variety of fruits and vegetables.
•
Eat fish, eggs, nuts, seeds, and beans instead of meats as a source of
protein.
•
Consume between one and two servings of low-fat dairy per day to obtain
calcium.
•
Drink no more than one (women) or two (men) alcoholic beverages (a
beer, a glass of wine, one mixed drink) per day.
Food Labels
•
The U.S. government requires all manufactured foods to carry two food labels:
– Ingredients label
– Nutrition facts label
•
The Ingredients Label
– Lists the chemical constituents of a food in descending order by weight
•
•
All the substances used, including other foods (e.g., grains, eggs)
•
Natural and artificial sweeteners
•
Natural and artificial fats
•
Natural and artificial thickeners
•
Natural and artificial flavorings
•
Food colorings
The Nutrition Facts Label
– Provides quantitative information on:
•
Certain nutrients (ingredients), whose consumption should be monitored
for good health
•
The calorie content of the food
•
Lists the percent daily value (PDV) of each nutrient; this is the percentage
of the recommended daily amount that is contained in the food.
Three Functions of Food
1. To provide the chemical constituents of the body and regulate body functions
– The body is made up of many atoms and molecules, many of which are replaced
constantly.
– There are 40 nutrients that are considered “essential nutrients.”
•
These must be supplied by food.
– Nutritional deficiency diseases occur when adequate amounts of the proper
nutrients are not obtained.
– A deficiency of only one nutrient can impair the body’s ability to use all others,
even if the others are present in sufficient amounts.
– Recommended (daily) dietary allowances (RDAs) outline the nutrient
requirements of most Americans.
– RDAs are set by the Food and Nutrition Board of the National Academy of
Sciences.
2. To provide energy for life
– Energy is measured in calories.
•
One calorie is the energy required to raise the temperature of 1 g of water
from 14.5°C to 15.5°C.
•
A kilocalorie is equivalent to 1,000 calories.
•
When we hear the word calorie used, we are actually referring to a
kilocalorie.
– Energy from food is derived from the breakdown of carbohydrates (4kcal/g), fats
(9kcal/g), and proteins (4kcal/g).
– Metabolism is the process of breaking down molecules to derive energy and
obtain material for the manufacture of cellular molecules.
– Energy is needed for
•
Basal Metabolism
– Basal metabolism is the minimum energy needed just to keep the
body alive at complete rest.
– Daily calorie need is called basal metabolic rate (BMR), which is
about 1,100 calories per day for women and about 1,300 calories
per day for men.
•
Physical Activity
– These are the things you do when you are not completely at rest
such as walking, running, working, etc.
– The amount of energy expended depends on how strenuous the
activity is, how long it is engaged in, the body’s size, and the
environmental temperature.
•
Growth and Repair
– For new cells that the body makes to combat illness or injury
3. To Provide Pleasure
– Hunger is not the only reason we eat in our society.
– Most of the time, we eat because it is “time to eat,” because food has been put in
front of us, because it feels good, or because it is an enjoyable social ritual.
– Advertising encourages us to eat more often.
•
For example, the “fourth meal”
Seven Components of Food
•
Digestion
– The mouth is the initial site of digestion.
– Chewed and softened food is passed from the mouth via the esophagus to the
stomach for additional breakdown.
– Nutrients are absorbed from the intestines into the blood.
– The liver regulates the release of nutrients.
– Nondigested material is excreted in feces.
1. Proteins
– Makes up 20% of your body mass
– Made up of chemical units called amino acids (20 total)
•
Essential (9)—those that must come from food (our body can’t make
them)
•
Nonessential (11)—those that the body can make, therefore, not
specifically required in the diet.
•
Complete protein—contains all of the essential amino acids
– The body does not store these in an acceptable amount, therefore, they must be
supplied from our diet.
•
Men—55–60 g/day
•
Women—45 g/day
•
The average North American consumes twice this amount.
– The amino acid composition of animal protein is similar to ours so we tend to
acquire most essential amino acids from animal tissue (fish, meat, eggs, and
dairy).
– The amino acid composition in vegetables is usually lacking in one essential
amino acid, so those who eat little or no meat must work to put vegetables
together that compensate for essential amino acids that are missing from each.
•
For example, beans and rice together make a complete protein (one that
contains all the essential amino acids).
2. Carbohydrates
– The major source of the body’s energy
– Simple Sugars
•
Glucose
•
Fructose
•
Sucrose
•
Lactose
– Complex Carbohydrates
•
Starch
•
Fiber
– Simple Sugars
•
A class of carbohydrates called monosaccharides
•
Simple sugars are made of one or two molecules only.
•
All carbohydrates must be reduced to simple sugars to be digested.
•
Glucose—most common simple sugar, found in all plants and animals,
circulates in the blood stream because the body converts all sugars to
glucose
•
Fructose—one of the sweetest sugars, e.g., high fructose corn syrup
•
Sucrose = Glucose + Fructose—table sugar
•
Lactose = Glucose + Galactose
– Needs lactase to break it down; milk allergy
– Complex Carbohydrates
•
A class of carbohydrates called polysaccharides
•
Starch—digestible
– Many glucose molecules linked together
– Glycogen—storage form of glucose in animals
– Animals and humans produce a starch in muscle and liver tissue
called glycogen.
– Glycogen breaks down when the organism needs glucose to
produce energy.
•
Fiber—nondigestible
– Soluble—dissolves in water
– Insoluble—doesn’t dissolve in water
– Recommended intake: 20–35g/day
– Fiber decreases the time material spends in the gastrointestinal (GI)
tract, reducing the risk of diverticular disease and cancer of the
colon and rectum.
– Most of your calories should come from carbohydrates.
– A low/no-carb diet is not recommended since our bodies run mostly off of carbs.
– What have you heard about carbohydrates?
– Can you differentiate between good and bad carbohydrates? Give some examples
from your cafeteria.
– What can you do to eat the good carbohydrates more often?
3. Lipids (Fats)
– A group of substances that are all insoluble in water.
– Triglyceride (body fat)
– Cholesterol, a fat-like compound that occurs in bile, blood, brain and nerve tissue,
liver, and other parts of the body
– Lecithin, which is essential to cell membranes
– Steroid hormones
– Vitamins A, D, E, and K
– Bile acids
– Triglyceride (body fat)
•
Composed of fatty acids
– Saturated—Completely bound to hydrogen
•
Found in animal fats, whole dairy products, and
hydrogenated vegetable shortening
•
“Bad fat”
– Monounsaturated—One less than the maximum number of
hydrogen bonds
•
Olive oil, some nuts
•
“Good fat”
– Polyunsaturated—More than one less than the maximum number
of hydrogen bonds
•
Fatty fish and safflower, cottonseed, corn, soybean, and
sesame seed oils
•
•
“Good Fat”
It is recommended that individuals consume no more than 300 mg/day of
cholesterol and limit saturated fat intake to 10% or less of total calories.
4. Vitamins
– Substances that facilitate (but don’t cause) a variety of biological processes (e.g.,
vitamin B supplements)
– Do not provide building blocks of tissues
– Do not provide calories
– Must be obtained from food
– Two types of vitamins
•
Water Soluble—C, Bs
•
Fat Soluble—A, D, E, K
– Antioxidants (vitamins A, C, and E) are substances that can inhibit
the oxidation of free radicals.
5. Minerals
– Inorganic substances that assist body functions
– Found in almost all food, especially vegetables
– Important ones that many are deficient in
•
Iron
•
Calcium
– Many people consume too much sodium because of all the processed foods they
eat; high sodium intake contributes to high blood pressure.
6. Phytochemicals
– Nonnutrients which come from plants that positively affect human physiology
– Help destroy and eliminate toxins acquired from the environment
7. Water
– Water, an essential nutrient, is a major component of cells and blood.
– Body water is maintained by sophisticated control mechanisms.
– Inadequate levels of body water (dehydration) lead to thirst.
– Excessive levels of body water causes hormone stimulation of the kidneys,
leading to additional urine production.
Dietary Supplements
•
More than 250,000 dietary supplements are available in the United States.
•
A dietary supplement provides one or more of the 40 essential nutrients, or nonessential
vitamins, minerals, enzymes, amino acids, herbs, hormones, and nucleic acids.
•
If you follow the recommendations from the Food Guide Pyramid, you are likely to
receive all the essential nutrients needed.
•
Those who may need dietary supplements are
– People who tend to skip meals, or eat a lot of processed or fast food
– People who consume an unusual or low-calorie diet for weight loss
– People who consume nutritionally inadequate diets for reasons of economic
hardship
– Athletes who are concerned with body size
– People who consume large amounts of coffee and/or alcohol
– Vegetarians (B12)
– Those who are lactose intolerant
– Women of childbearing age who don’t consume enough folic acid or calcium
•
Many dietary supplements are touted by drug companies as preventatives or cures for all
sorts of aches and ailments.
•
Unlike prescription and OTC medications, dietary supplements do not have to be tested
before going to market.
•
Harmful impurities—ingredients may be added of which you are unaware.
•
Harmful supplements—many dietary supplements for weight loss have been taken off the
market after complications from their use were discovered.
Food Additives
•
Most manufactured foods contain additives for:
– Texture
– Stability
– Flavor
– Color
– Longer shelf life
– Sales appeal
•
Common additives:
– Artificial sweeteners
•
Acesulfame K
•
Sucralose
•
Saccharin
•
Aspartame
– Preservatives
•
BHA, BHT, and sodium nitrate
•
Sulfites (in wine, salad)
Food Safety
•
Food contaminated with the bacterium Escherichia coli O157:H7 is responsible for
thousands of cases of illness.
•
Food contaminated with Salmonella species causes more than 1 million Americans to
become ill annually.
•
Symptoms of bacterial food poisoning are headache, nausea, and fever.
•
Each day, about 20% of the U.S. population, or 46 million people, eat at a fast-food
restaurant.
•
Fast-food choices must be made carefully because many contain:
– Large quantities of saturated fat
– Large quantities of cholesterol
– Large quantities of salt
– Few complex carbohydrates
– Inadequate amounts of vitamins A and C
Vegetarian Diets
•
Research indicates that vegetarians are generally at lower risk than nonvegetarians for
coronary heart disease, hypertension, some forms of cancer, noninsulin-dependent
diabetes, and obesity.
•
Three types:
– Vegan, or strict vegetarian, diets exclude all animal products, including milk,
cheese, eggs, and other dairy products.
– Lacto-vegetarian diets exclude meat, poultry, fish, and eggs but include dairy
products.
– Lacto-ovo-vegetarian diets exclude meats, poultry, and seafood but include eggs
and dairy products.
How Nutrition Affects the Brain
•
Diet can affect levels of neurotransmitters in the brain.
•
Serotonin levels increase after ingesting tryptophan.
•
Acetycholine levels increase after ingesting choline.
•
High sugar intake can cause a low blood sugar reaction, or reactive hypoglycemia.
Choosing a Nutritious Diet
•
Take some time to explore the MyPyramid Web site.
•
Are you eating according to their recommendations?
•
What category do you struggle with the most?
•
How can you make small changes to do better in that category?
Study Guide and Self-Assessment Workbook
5.1 My Estimated Daily Calorie Requirement
5.2 My Food Diary
5.3 My Dietary Analysis
5.4 Fast Food Restaurant Research
5.5 Can I Read a Food Label?
Additional Resources
Food and Nutrition Board
Institute of Medicine
2101 Constitution Avenue NW
Washington, DC 20418
(202) 334-2000
http://www.iom.edu/CMS/3788.aspx
Food and Nutrition Information Center
Agricultural Research Service
National Agriculture Library Room 304
10301 Baltimore Ave.
Beltsville, MD 20705-2351
www.nal.usda.gov/fnic
USDA Center for Nutrition Policy and Promotion
3101 Park Center Drive
Room 1034
Alexandria, VA 22302-1594
http://www.mypyramid.gov/index.html
Vegetarian Resource Group
P.O. Box 1463
Baltimore, MD 21203
(410) 366-8343
www.vrg.org
Willett, W.C. & Stampfer, M.F. (2003). Rebuild the food pyramid. Scientific American, January,
64–71.