Transcript Ch. #12: Nutrition Basics

Chapter Twelve
Nutrition Basics
Nutrients
•Essential nutrients = substances the body
must get from food because it cannot
manufacture them at all or fast enough to
meet its needs:
–
–
–
–
–
–
Proteins
Carbohydrates
Fats
Vitamins
Minerals
Water
Energy from Food
• Kilocalorie = a measure of energy content in food; the
amount of heat it takes to raise the temperature of 1
liter of water 1°C; commonly referred to as “calorie”
• Three classes of essential nutrients supply energy
– Fat = 9 calories per gram
– Protein = 4 calories per gram
– Carbohydrates = 4 calories per gram
Proteins—The Basis of Body
Structure
• Protein = a compound made of amino acids that
contains carbon, hydrogen, oxygen, and nitrogen
• Of twenty common amino acids in foods, nine
are essential
• Proteins form key parts of the body’s main
structural components—muscles and bones—and
of blood, enzymes, cell membranes, and some
hormones
Complete and Incomplete
Proteins
• Complete protein sources = foods that supply all
the essential amino acids in adequate amounts
– Meat, fish, poultry, eggs, milk, cheese, and soy
• Incomplete protein sources = foods that supply
most but not all essential amino acids
– Plants, including legumes, grains, and nuts
Recommended Protein Intake
• Adequate daily intake of protein = 0.8
gram per kilogram (0.36 gram per pound)
of body weight
• Acceptable Macronutrient Distribution
Range = 10–35% of total daily calories as
protein
Fats—Essential in Small
Amounts
• Fats supply energy, insulate the body, support and
cushion organs, absorb fat-soluble vitamins, add
flavor and texture to foods
• Essential fats (linoleic acid and alpha-linolenic
acid) are key regulators of body process such as
the maintenance of blood pressure and the
progress of a healthy pregnancy
Types and Sources of Fats
• Saturated fat = a fat with no carbon-carbon double
bonds; usually solid at room temperature
– Found primarily in animal foods and palm and coconut oils
• Monounsaturated fat = a fat with one carbon-carbon
double bond; usually liquid at room temperature
– Found in certain vegetables, nuts, and vegetable oils
• Polyunsaturated fat = a fat with two or more carboncarbon double bonds; usually liquid at room
temperature
– Found in certain vegetables, nuts, and vegetable oils and in
fatty fish
Types and Sources of Fats
• Two key forms of polyunsaturated fats:
– Omega-3 fatty acids = the endmost double bond
of a polyunsaturated fat occurs three carbons
from the end of the fatty acid chain
• Found primarily in fish
– Omega-6 fatty acids = the endmost double bond
of a polyunsaturated fat occurs six carbons from
the end of the fatty acid chain
• Found primarily in certain vegetable oils, especially
corn, soybean, and cottonseed oils
Trans Fatty Acids
• The process of hydrogenation, in which
hydrogens are added to unsaturated fats, produces
a mixture of saturated fatty acids and standard
and trans forms of unsaturated fatty acids
• Trans fatty acids have an atypical shape that
affects their chemical activity
Trans Fatty Acids
Fats and Health
• Fats affect blood cholesterol levels
– Low-density lipoprotein (LDL) = “bad” cholesterol
– High-density lipoprotein (HDL) = “good” cholesterol
• Saturated and trans fats raise levels of LDL;
trans fats also lower levels of HDL
• Unsaturated fats lower levels of LDL
Fats and Health
• Fats also affect triglyceride levels,
inflammation, heart rhythm, blood pressure,
and cancer risk
• Best choices = monounsaturated fats
and polyunsaturated omega-3 fats
• Limit intake of saturated and trans
fats
Saturated and Trans Fats: Comparing
Butter and Margarine
Butter
Stick
margarine
Margarine
spread
Saturated fat
Trans fat
Other fats
Tub
margarine
Squeeze
margarine
0
5
10
Grams of fat in 1
tablespoon
15
SOURCE: Food an Drug Administration
Total fat grams per serving
Total, Saturated, and Trans Fat
Content of Selected Foods
Other fats
Trans fat
Saturated fat
30
25
20
15
10
5
0
French fries
Doughnut
Pound cake Potato chips
Candy bar
Milk (whole)
SOURCE: Food an Drug Administration
Recommended Fat Intake
• Adequate daily intake of fat:
Men
Women
Linoleic acid
17 grams
12 grams
Alpha-linolenic acid
1.6 grams
1.1 grams
= about 3–4 teaspoons of vegetable oil
• Acceptable Macronutrient Distribution Range =
20–35% of total daily calories as fat
Carbohydrates—An Ideal Source
of Energy
• The primary function of dietary carbohydrate is to
supply energy to body cells.
• Cells in the brain, nervous system, and blood, use only
carbohydrates for fuel
• During high-intensity exercise, muscles get most of
their energy from carbohydrates
• During digestion, carbohydrates are broken into single
sugar molecules such as glucose for absorption; the liver
and muscles take up glucose and store it in the form of
glycogen
Simple and Complex
Carbohydrates
• Simple carbohydrates contain one or two sugar
units in each molecule
– Found naturally in fruits and milk and added to many
other foods
– Include sucrose, fructose, maltose, and lactose
• Complex carbohydrates consist of chains of many
sugar molecules
– Found in plants, especially grains, legumes, and tubers
– Include starches and most types of dietary fiber
Whole Grains
 Before they are processed, all
grains are whole grains
consisting of an inner layer of
germ, a middle layer called the
endosperm, and an outer layer
of bran
 During processing, the germ
and bran are often removed,
leaving just the starchy
endosperm
 Refined carbohydrates usually
retain all the calories of a whole
grain but lose many of the
nutrients
Refined Carbohydrates Versus
Whole Grains
• Whole grains are higher than refined carbohydrates
in fiber, vitamins, minerals, and other beneficial
compounds
• Whole grains take longer to digest
– Make people feel full sooner
– Cause a slower rise in glucose levels
• Choose foods that have a whole grain as the first
item on the ingredient list on the label
– Whole wheat, whole rye, whole oats, oatmeal, wholegrain corn, brown rice, popcorn, barley, etc.
Glycemic Index
• Consumption of carbohydrates causes insulin and
glucose levels in the blood to rise and fall
• Glycemic index = a measure of how the ingestion of
a particular food affects blood glucose levels
• Foods with a high glycemic index cause quick and
dramatic changes in glucose levels
• Diets rich in high glycemic index foods are linked to
increased risk of diabetes and heart disease
Recommended Carbohydrate Intake
• Adequate daily intake of carbohydrate = 130 grams
• Acceptable Macronutrient Distribution Range = 45–
65% of total daily calories as carbohydrate
• Limit on intake of added sugars
– Food and Nutrition Board: 25% or less of total daily calories
– World Health Organization: 10% or less of total daily calories
– MyPyramid: 32 grams (8 tsp) in a 2000-calorie diet
Acceptable Macronutrient
Distribution Ranges: Summary
• Protein =
10–35% of total
daily calories
• Fat =
20–35% of total
daily calories
• Carbohydrate = 45–65% of total
daily calories
Fiber—A Closer Look
• Dietary fiber = nondigestible carbohydrates and
lignin that are present naturally in plants
• Functional fiber = nondigestible carbohydrates
isolated from natural sources or synthesized in a
lab and added to a food or supplement
• Total fiber = dietary fiber + functional fiber
• Fiber does not provide calories
Types of Fiber
• Soluble (viscous) fiber = fiber that dissolves in
water or is broken down by bacteria in the large
intestine (oat bran, legumes)
– Slows the body’s absorption of glucose
– Binds cholesterol-containing compounds
• Insoluble fiber = fiber that doesn’t dissolve in
water (wheat bran, psyllium seed)
– Makes feces bulkier and softer
– Helps prevent constipation, hemorrhoids, and
diverticulitis
Sources of Fiber
• All plant foods contain fiber, but processing can
remove it
• Good sources of fiber:
–
–
–
–
–
–
Fruits (especially whole, unpeeled fruits)
Vegetables
Legumes
Oats (especially oat bran)
Whole grains and wheat bran
Psyllium (found in some cereals and laxatives)
Recommended Intake of Fiber
• Women = 25 grams per day
• Men = 38 grams per day
• Americans currently consume about half
this amount
Vitamins—Organic Micronutrients
• Vitamins = organic (carbon-containing) substances
needed in small amounts to help promote and regulate
chemical reactions and processes in body cells.
• Four vitamins are fat-soluble (A, D, E, and K)
• Nine vitamins are water-soluble (C and the eight Bcomplex vitamins: thiamin, riboflavin, niacin, vitamin B-6,
folate, vitamin B-12, biotin, and pantothenic acid)
Vitamins
• Vitamins are abundant in fruits, vegetables,
and grains; they are also added to some
processed foods
• If you consume too much or too little of a
particular vitamin, characteristic symptoms of
excess or deficiency can develop
Minerals—Inorganic Micronutrients
• Minerals = inorganic (non-carbon-containing)
compounds needed in small amounts for
regulation, growth, and maintenance of body
tissues and functions
• There are about 17 essential minerals:
– Major minerals (those that the body needs in amounts
exceeding 100 mg per day) include calcium,
phosphorus, magnesium, sodium, potassium, and
chloride
– Essential trace minerals include copper, fluoride,
iodide, iron, selenium, and zinc
Minerals
• If you consume too much or too little of a
particular mineral, characteristic symptoms of
excess or deficiency can develop
• Minerals commonly lacking in the American diet:
– Iron = low intake can cause anemia
– Calcium = low intake linked to osteoporosis
– Potassium = low intake linked to elevated blood
pressure and bone mineral loss
– Magnesium
Osteoporosis—Thinning of Bones
• Dietary factors that build bone
mass:
–
–
–
–
Calcium
Vitamin D
Vitamin K
Other possible dietary factors:
vitamin C, magnesium, potassium,
manganese, zinc, copper, boron
• Weight-bearing exercise and
strength training also build and
maintain bone mass
• Dietary factors linked
to loss of bone mass:
–
–
–
–
–
–
Alcohol
Sodium
Caffeine
Retinol
Soda
Protein (if intake of
calcium and vitamin D
is low)
Water—A Vital Component
• Human body is composed of about 50–60% water; you
can live only a few days without water
• Foods and fluids you consume provide 80–90% of your
daily water intake
• Adequate intake to maintain hydration:
– Women = about 9 cups of fluid per day
– Men = about 13 cups of fluid per day
• Drink in response to thirst; consume additional fluids for
heavy exercise
Other Substances in Food:
Antioxidants
• Antioxidant = a substance that protects against the
breakdown of body constituents by free radicals; actions
include binding oxygen, donating electrons to free radicals,
and repairing damage to molecules
– Free radical = a chemically unstable, electron-seeking compound
that can damage cell membranes and mutate genes in its search for
electrons
• Many fruits and vegetables are rich in antioxidants such as
vitamin C, vitamin E, selenium, and carotenoids
Other Substances in Food:
Phytochemicals
• Phytochemical = a naturally occurring substance found in
plant foods that may help prevent and treat chronic
diseases
• Examples:
– Certain proteins in soy foods
– Sulforaphane in cruciferous vegetables (cabbage, broccoli,
brussels sprouts, kale, cauliflower)
– Allyl sulfides in garlic and onions
• Fruits and vegetables are rich in phytochemicals
Nutritional Guidelines: Planning
Your Diet
• Dietary Reference Intakes (DRIs) = standards for
levels of nutrient intake to prevent nutrient deficiencies
and reduce the risk of chronic disease
• Dietary Guidelines for Americans = general principles
of good nutrition intended to help prevent certain dietrelated diseases
• MyPyramid = a food-group plan that provides practical
advice to ensure a balanced intake of essential nutrients
Dietary Reference Intakes (DRIs)
• Set by the Food and Nutrition Board of the National
Academies
• Recommended Dietary Allowance (RDA) or Adequate
Intake (AI) = recommended intake
• Tolerable Upper Intake Level (UL) = maximum daily
intake unlikely to cause health problems
• Example of calcium recommendations for an 18-yearold woman:
– RDA = 1300 mg/day
– UL = 2500 mg/day
Should You Take Supplements?
• The Food and Nutrition Board recommends
supplements only for certain groups:
– Folic acid for women capable of becoming pregnant
(400 µg/day)
– Vitamin B-12 for people over age 50 (2.4 mg/day)
• Other possible situations for supplements:
–
–
–
–
Vitamin C for smokers
Iron for menstruating women
Vitamin K for newborns
People with certain special health concerns
Daily Values
• Daily Values = a simplified version of the RDAs
used on food labels
• Also included in Daily Values are standards for
nutrients with no established RDA
• Shown on food labels in terms of a 2000-calorie
diet
Dietary Guidelines for Americans
• Adequate Nutrients within Calorie Needs
– Focus on nutrient dense foods.
– Eat more dark green vegetables, orange vegetables,
legumes, fruits, whole grains, and low-fat and fat-free
milk and milk products.
– Eat less refined grains, saturated fat, trans fat,
cholesterol, added sugars, and calories.
– Plans that meet the goals include MyPyramid and
DASH.
Dietary Guidelines for Americans
• Weight Management
– Evaluate body weight in terms of BMI.
– Balance food intake and physical activity to avoid
weight gain.
– To lose weight, decrease calorie intake, maintain
adequate nutrient intake, and increase physical activity.
Dietary Guidelines for Americans
• Physical Activity
– 30 minutes per day to reduce risk of chronic disease
– 60 minutes per day to prevent weight gain
– 60-90 minutes per day to sustain weight loss
Dietary Guidelines for Americans
• Food Groups to Encourage
– Fruits and vegetables—choose a variety of colors and
kinds
– Whole grains—half of all servings of grains should be
whole grains
– Low-fat and fat-free milk and milk products
Dietary Guidelines for Americans
• Fat Intake Goals
– Total fat: 20-35% of total daily calories
– Saturated fat: Less than 10% of total daily
calories
– Trans fat: As little as possible
– Cholesterol: Less than 300 mg per day
Dietary Guidelines for Americans
• Carbohydrate Intake
– Choose high-fiber foods
– Limit intake of added sugars
• Sodium and Potassium
– Limit sodium intake (2300 mg per day; 1500 mg
per day for those at high risk)
– Consume adequate potassium
• Alcohol intake—moderate if at all
MyPyramid
• Food guidance system that promotes healthy
food choices and physical activity
• Choosing a balance of servings from different
food groups meets nutrient needs and reduces
chronic disease risk
• Balancing food choices and activity promotes
weight management
MyPyramid
MyPyramid: Grains
• For a 2000-calorie diet, choose 6 ounceequivalents per day
• 1 ounce-equivalent:
–
–
–
–
–
1 slice of bread
1 small muffin
1 cup ready-to-eat cereal flakes
1/2 cup cooked cereal, rice, grains, pasta
1 6-inch tortilla
MyPyramid: Vegetables
• For a 2000-calorie diet, choose 2-1/2 cups (5
servings) per day
• 1/2 cup or equivalent:
– 1/2 cup raw or cooked vegetables
– 1/2 cup vegetable juice
– 1 cup raw leafy salad greens
MyPyramid: Vegetables
• Choose vegetables from five groups:
– Dark green vegetables (spinach, kale, collards, bok
choy, other leafy greens)
– Orange and deep yellow vegetables (carrots, winter
squash, sweet potatoes)
– Legumes
– Starchy vegetables (corn, potatoes, peas)
– Others (e.g., tomatoes, bell peppers, green beans,
cruciferous vegetables)
MyPyramid: Fruits
• For a 2000-calorie diet, choose 2 cups (4
servings) per day
• 1/2 cup or equivalent:
–
–
–
–
1/2 cup fresh, canned, or frozen fruit
1/2 cup fruit juice (100% juice)
1 small whole fruit
1/4 cup dried fruit
• Choose whole fruits often
MyPyramid: Milk
• For a 2000-calorie diet, choose 3 cups or the
equivalent per day
• 1 cup or equivalent:
–
–
–
–
1 cup milk or yogurt
1/2 cup ricotta cheese
1-1/2 ounces natural cheese
2 ounces processed cheese
• Choose low-fat and fat-free items
MyPyramid: Meat and Beans
• For a 2000-calorie diet, choose 5-1/2 ounceequivalents per day
• 1-ounce equivalents:
–
–
–
–
–
1 ounce cooked lean meat, poultry, fish
1/4 cup tofu or cooked legumes
1 egg
1 tablespoon peanut butter
1/2 ounce nuts or seeds
• Choose lean cuts, limit serving sizes, and try one
plant protein source daily
MyPyramid: Oils
• For a 2000-calorie diet, choose 6 teaspoons per
day
• 1 teaspoon or equivalent:
– 1 teaspoon vegetable oil or soft margarine
– 1 tablespoon salad dressing or light mayonnaise
– Food sources: 8 large olives, 1/6 medium avocado,
1/2 tablespoon peanut butter, 1/3 ounce roasted
nuts
MyPyramid: Discretionary Calories
• If nutrient-dense forms are selected from food
groups, the remaining discretionary calories may
be used to increase intake of fats or added
sugars.
The Vegetarian Alternative
• Types of vegetarian diets
– Vegan = vegetarian who eats no animal products
– Lacto-vegetarian = vegetarian who includes milk and
cheese products in the diet
– Lacto-ovo-vegetarian = vegetarian who includes milk and
cheese products and eggs in the diet
– Partial vegetarian, semivegetarian, or pescovegetarian =
vegetarian who includes eggs, dairy products, and small
amounts of poultry and seafood in the diet
Vegetarian Diets and Health
• Vegetarian diets are lower in saturated fat and
cholesterol and higher in complex
carbohydrates, fiber, folate, vitamins C and E,
carotenoids, and phytochemicals
• Nutrients of concern for vegetarians include
vitamin B-12, vitamin D, calcium, iron, and zinc
Dietary Challenges for Special
Population Groups
•
•
•
•
•
Women—nutrient density, calcium, iron
Men—fruits, vegetables, grains
College students—overall quality of food choices
Older adults—nutrient density, fiber, vitamin B-12
People with special health concerns— discuss
with physician or dietitian
Food Labels
Read labels to
learn more
about
your food choices.
Dietary Supplements
• May contain powerful bioactive chemicals
• Not regulated the way drugs are by the FDA in
terms of testing and manufacture
• May interact with prescription and over-thecounter drugs and supplements
Foodborne Illness
• Most foodborne illness is caused by pathogens (diseasecausing microorganisms)
• You can’t tell by taste, smell, or sight whether a food is
contaminated
• To prevent foodborne illness, handle, cook, and store
foods in ways that prevent microorganisms from
spreading and multiplying
• New threat: bovine spongiform encephalopathy (BSE
or “mad cow disease”)
Food
Safety
• Cook foods to an
appropriate temperate
• Keep hot foods hot
and cold foods cold
Organic Foods
Organic = a designation applied to foods grown
and produced according to strict guidelines limiting
the use of pesticides, nonorganic ingredients,
hormones, antibiotics, genetic engineering,
irradiation, and other practices

 Organic foods tend to
have lower levels of
pesticide residues than
conventionally grown
crops
Environmental Contaminants
• Follow FDA/EPA limits for fish consumption
to avoid consuming excess mercury
• Consider the sources of fish (farmed vs. wild)
Food Additives
• Most widely used are sugar, salt, corn syrup, citric
acid, baking soda, vegetable colors, mustard,
pepper
• Concerns about some additives:
– Monosodium glutamate (MSG) causes some people to
experience episodes of sweating and increased blood
pressure
– Sulfites cause severe reactions in some people
– Check food labels
Irradiated Foods—A Technique
of Biotechnology
• Food irradiation = treatment
of foods with gamma rays, X
rays, or high-voltage
electrons to kill potentially
harmful pathogens and
increase shelf life
Genetically Modified Foods
• GM organism = a plant, animal, or
microorganism in which genes have been
addded, rearranged, or replaced through genetic
engineering
• Many GM crops are already grown in the United
States (soybeans, corn)
• No labeling requirement unless a GM food
contains a known allergen
Food Allergies
• Reaction by the immune system to a food or
food ingredient
• Common food allergens include peanuts, milk,
eggs, tree nuts, soy, wheat, fish, and shellfish
• Severe allergic responses can include anaphylaxis
Food Intolerance
• More common than true food allergies
• Reaction to a food or food ingredient, usually based on
a problem with metabolism
• Common intolerances include lactose intolerance, in
which people are deficient in the enzyme lactase, and
gluten intolerance
• Problems can be avoided by avoiding or limiting trigger
foods
• Keep a food diary to help identify problems
A Personal Plan: Applying
Nutritional Principles
• Assess your current diet
• Set goals for change
• Try additions and substitutions to bring your
current diet closer to your goals
• Plan ahead for challenging situations
Chapter Twelve
Nutrition Basics