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Chapter Five
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 pyramid and its recommendations.
4. Explain how to use the My Pyramid website.
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 risks 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
Factors Affecting Nutrition
• 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 contains too much saturated and trans-fat, refined carbohydrates,
sugar, and salt.
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)
Dietary Guidelines for Eating Right
• The current dietary guidelines for Americans are set by the U.S. Departments of Agriculture
and Health and Human Services.
• These guidelines are designed to help prevent diseases that result from poor nutrition.
The USDA Food Guide Pyramid (www.MyPyramid.com)
• Released in 2005, MyPyramid is designed to be a flexible on-line tool.
• It encourages:
—Variety
—Moderation
—Proportions
—Physical activity
—Gradual improvements
—Personalization
The Healthy Eating Pyramid
• Daily exercise to control weight and maintain physical and mental health.
• Replace saturated fat, cholesterol, and trans-fats in manufactured and restaurant foods with
polyunsaturated fats in canola, olive, sunflower and corn oil.
• Replace refined grains with whole grains.
• Consume more than five servings per day 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
• 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
• Nutrition facts label provides quantitative information on:
—Certain nutrients (ingredients), whose consumption should be monitored for good health.
—The calorie content of the food.
—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
• To provide the chemical constituents of the body and regulate body functions
• To provide the energy for life
ª To provide pleasure
Providing Chemical Constitution
• Every person is made up of a particular number and combination of atoms and molecules.
• Forty essential nutrients are obtained from food.
• Nutritional deficiency diseases occur if not enough of the proper nutrients are obtained.
• A deficiency of only one nutrient can impair the body’s ability to use all other nutrients, even if
they 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.
Energy for Life
• Food is the source of energy for life.
• Energy is measured in calories.
—One calorie is the energy required to raise the temperature of 1 gram of water from 14.5°C
to 15.5°C.
• Nutritional calorie is a unit of energy often referred to as a kilocalorie.
—A kilocalorie is equivalent to 1,000 calories.
• Amount of energy needed depends on:
—How strenuous the activity is
—Body weight
—Environmental temperature
• Basal metabolism is the minimum energy needed to keep the body alive.
• Daily calorie need is called basal metabolic rate (BMR), which is about 1100 calories per day
for women and about 1300 calories per day for men.
Seven Components of Food
• Proteins
• Carbohydrates: simple sugars and complex carbohydrates
• Lipids (fats)
• Vitamins
• Phytochemicals
• Minerals
• Water
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.
Proteins
• Important proteins include enzymes, antibodies, hemoglobin, and some hormones.
• Proteins are involved in virtually all essential parts and functions of the body: skeleton, hair,
nails, chemical reactions, antibodies, hemoglobin and cell receptors.
• Proteins are made up of amino acids linked together in chains.
• There are 20 different amino acids.
• Optimal protein synthesis requires all amino acids in sufficient amounts.
• Amino acids are classified as essential and nonessential.
Amino Acids
• Eight essential amino acids are required by adults and nine are required by infants.
• Obtain the eight essential amino acids from food.
• Generally supplied by daily intake of 45 to 60 grams of dietary protein.
• A daily supply is required because amino acids are not stored in the body.
• High-quality dietary protein matches the body’s needs for essential amino acids.
• Most vegetable protein has insufficient essential amino acids; protein from different vegetable
sources must be mixed to make complete protein.
Carbohydrates
• Carbohydrates are the principal source of the body’s energy.
• Carbohydrates are also used to manufacture deoxyribonucleic acid (DNA).
• Carbohydrates are needed in diets to prevent breakdown of body protein (i.e., muscle tissue).
• Two types: simple and complex.
—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.
—Complex carbohydrates, a class of carbohydrates called polysaccharides.
Simple Sugars
• Glucose is the most common simple sugar and is found in all plants and animals.
• Glucose circulates in the bloodstream and is commonly referred to as blood sugar.
• It is the principal cellular energy source.
• The body converts all sugars to glucose.
• Other types of sugar are fructose, sucrose, lactose.
Complex Carbohydrates
• Two main classes.
—Starch (digestible)
—Fiber (non-digestible)
• 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
• Two types: soluble fiber and insoluble fiber.
• It is recommended that individuals consume 20 to 35 grams per day of fiber.
• Differences in insoluble and soluble fiber are not nutritionally significant.
• Fiber decreases the time material spends in the gastrointestinal (GI) tract, reducing the risk of
diverticular disease and cancer of the colon and rectum.
Lipids
• 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.
• Linoleic acid is an essential fat that must be obtained from food; it is found in safflower oil,
sunflower oil, and corn oil.
• A fat is classified as saturated, monounsaturated, or polyunsaturated.
• Saturation refers to the number of hydrogen atoms in the fatty acids.
• Unsaturated fats, including both monounsaturated and polyunsaturated fats, are derived from
plants.
• 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.
• Artificial fats are chemicals added primarily to packaged pastries and snack foods to provide
the taste of fat without contributing calories.
Vitamins
• Vitamins are biological molecules needed to facilitate many life-sustaining processes.
• Vitamins are classified as water-soluble vitamins or fat-soluble vitamins.
• There are nine water-soluble vitamins.
• There are four fat-soluble vitamins.
• Antioxidants (vitamins A, C, and E) are substances that can inhibit the oxidation of free
radicals.
Minerals
• Nonorganic chemical elements (minerals) are needed to facilitate many life functions.
• Minerals are found in nearly all foods.
• Eating a variety of foods, especially fresh fruits and vegetables, provides sufficient quantities.
• Too much sodium contributes to high blood pressure.
Phytochemicals
• Plant matter contains hundreds of chemical substances, called phytochemicals, that affect
human physiology.
• Phytochemicals help destroy and eliminate toxins acquired from the environment.
—Isoprenoids
—Flavonoids
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 kidneys, leading to additional
urine production.
Dietary Supplements
• More than 250,000 dietary supplements are available in the U.S.
• A dietary supplement intended to prevent or treat an illness is called a neutraceutical.
• Following the recommendations from the food guide pyramid typically provides all the
essential nutrients.
• Many dietary supplements are touted by drug companies as preventatives or cures for all sorts
of aches and ailments.
• Unlike prescription and over-the-counter medications, dietary supplements do not have to be
tested before going on the market.
• Harmful impurities, in the form of added ingredients.
• Harmful supplements; many dietary supplements for weight loss have been taken off the
market after causing complications.
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.
Fast Food
• 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 foods 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, non-insulin-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.
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/
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.