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Module II
AAEC 4984
Spring 2009
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The Basics of Food, Nutrition, and Health ......................................................................... 1
A. Nutrients and Nutrition ............................................................................................. 1 1. Why Should We Care About Nutrition?................................................................. 1 2. What Are the Nutrients in Foods? .......................................................................... 3 3. What Constitutes a Nutritious Diet? ..................................................................... 14
B. Foods and Nutrition.................................................................................................. 19 Food Classifications and Guidelines......................................................................... 23
C. Nutrient and Food Recommendations..................................................................... 25 MyPyramid ............................................................................................................... 33 Food Labels: Required Items .................................................................................... 36 Food Labels: Optional Items..................................................................................... 39
D. Diet and Health ....................................................................................................... 43 Diet and Cardiovascular Disease .............................................................................. 46 Diet and Cancer......................................................................................................... 50
E. A Foreshadowing Conclusion .................................................................................. 52
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The Basics of Food, Nutrition, and Health
In this module we review the basics of food, nutrition, and health as can be found in most
introductory nutrition books. There are many good introductory nutrition texts and for
this review we draw heavily from the textbook by Frances Sizer and Ellie Whitney
entitled Nutrition: Concepts and Controversies 11th Edition. Thomson-Wadsworth 2008.
We begin with a review of nutrients and then turn to the connection of nutrients to food,
and then the connection to health.
A. Nutrients and Nutrition
This sub-section is designed to answer three rather basic questions:
1. Why should we care about nutrition?
2. What are the nutrients in foods?
3. What constitutes a nutritious diet?
1. Why Should We Care About Nutrition?
The simple answer to this question is that there is a well established link between
nutrition and several chronic diseases. A chronic disease is defined as a long-duration
degenerative disease characterized by deterioration of the body organs. According to the
National Center for Health Statistics, the top 10 causes of death in 2005 are as listed in
table 1. Of these top 10 causes of death, the top three (i.e., Heart Disease, Cancers, and
Strokes), as well as Diabetes (No. 6), are known to be affected by diet.
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Table 1. Leading Causes of Death for U.S. 2005 Cause of death Deaths All causes 2,448,017 Heart Diseases 652,091 Cancers 559,312 Strokes 143,579 Chronic lower respiratory diseases 130,933 Unintentional injuries 117,809 Diabetes mellitus 75,119 Alzheimer's disease 71,599 Influenza and pneumonia 63,001 Nephritis, nephrotic syndrome and nephrosis 43,901 Septicemia 34,136
Source: Health United States, 2007. US Dept. of Health and Human Services
In percentage terms, these four disease categories accounted for over half of the deaths
(59%) in the United States in 2005 with the breakdown being: heart diseases 27%,
cancers 23%, strokes 6%, and diabetes 3%.
Because these diseases are known to be related to diet, the implication is that by
altering the diet, the risk of contracting and/or dying from these diseases may be altered
as well. Consequently, the risk of contracting and dying from these diseases will be
increased by consuming one type of diet whereas the risk can be decreased by consuming
another type of diet.
What do we mean by the term diet? We will define diet to be the foods and beverages
a person usually eats or drinks. A diet is not the foods and beverages for a single meal.
A happy meal from McDonald’s is not a diet. A diet is more like a “typical” or
“average” meal a person may eat over say a week or a month. Note however, in a typical
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Wal Mart Superstore grocery section there are over 30,000 different food items. It is
impractical and also irrelevant to try to classify diets based on food items because what is
important for the body and health are the basic components of the foods, called nutrients,
which are much fewer in number than the number of food items.
2. What Are the Nutrients in Foods?
Technically, nutrients are families of molecules in food or components of food that are
indispensible for the functioning of the body. Conceptually, nutrients are just attributes
or characteristics that are common to all foods and thus are useful as a classification
scheme for foods that may seem very different, such as apples and oranges.
Consequently a diet also could be defined as the foods and beverages or nutrients a
person usually eats or drinks.
The body requires six kinds of nutrients or nutrient classes: 1
1. Water 4. Proteins
2. Carbohydrates 5. Vitamins
3. Fats 6. Minerals
Water needs no introduction or definition. Carbohydrates are compounds that are
composed of sugars. They can be classified by their number of sugar units: one unit
(monosaccharides such as glucose and fructose), two units (disaccharides such as sucrose
and lactose) and multiple units (polysaccachrides such as starch, glycogen, and cellulose).
Fats are lipids (organic compounds soluble in organic solvents but not water) that are
solid at the room temperature of 70o F. Fats are usually further broken down into
1 A typical Nutrition textbook will have individual chapters devoted to each of the nutrient classes with a discussion of the chemical elements and compounds for each and how these are processed by body. This decompositional detail is not viewed as critical for the main purpose of this review.
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saturated fatty acids and unsaturated fatty acids. The difference has to do with how the
hydrocarbon chains are connected. Proteins are organic compounds consisting of amino
acids that are joined by peptide bonds. Vitamins are organic compounds that are vital to
life and indispensible to body functions but only needed in minute amounts. There are 14
vitamins: Vitamin A, Thiamin B1, Riboflavin B2, Niacin B3, Vitamin B6, Vitamin B12,
Biotin, Pantothenic acid, Vitamin C, Vitamin D, Vitamin E, Vitamin K, Folate, and
Choline. Finally, minerals are naturally occurring, inorganic, homogeneous substances
or chemical elements. There are 15 minerals of main concern for nutrition: calcium,
chromium, copper, fluoride, iodine, iron, magnesium, manganese, molybdenum,
phosphorous, selenium, zinc, potassium, sodium, and chloride.2 The first four nutrient
classes are required in relatively large amounts and are called macronutrients. Vitamins
and minerals are required in much smaller quantities and are called micronutrients. The
micronutrients, vitamins and minerals do not provide energy but act as regulators in the
body. Vitamins and minerals assist in numerous body processes, such as digesting food,
moving muscles, disposing of waste, growing new tissue and healing wounds.
Note because all foods have these six nutrients in some percentage (remembering
zero is also a percentage) a diet could also be defined as the usual combination of
nutrients an individual consumes. All six classes of nutrients have what are called
essential nutrients. Essential nutrients are nutrients the body cannot make for itself
from other raw materials and must be obtained from food to prevent deficiencies.
With the exception of Water, the macronutrients provide fuel or energy for the body
to function. Energy is defined as the capacity to do work. Food energy is measured in
calories. A calorie (short for kilocalorie) is technically defined as the amount of heat 2 These are the minerals listed in the DRI tables. See next section for discussion of DRI.
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energy necessary to raise the temperature of a kilogram (one liter) of water one degree
Celsius. For a standard weight the macronutrients (excluding water) each provides a
certain calorie or amount of energy. The standard unit of weight used in nutrition is the
gram(g), which is defined as the weight of a milliliter (ml) of water with defined
conditions of temperature and pressure. One gram equals about .04 ounces or 28 grams
equals about 1 ounce. Carbohydrates and Proteins each provide 4 calories per gram,
whereas Fats provide 9 calories per gram. Table 2 provides a succinct classification of
the nutrient classes.
Table 2. Main Nutrient Classes 6 Nutrient Classes Macro Micro Energy Yielding Cal/g
1. Water X 2. Carbohydrate X X 4 3. Fat (Lipids) X X 9 4. Protein X X 4 5. Vitamins X 6. Minerals X
Individual Food Items: Nutrient and Energy Characteristics
Knowing the calories per gram of the nutrients allows the total energy or calories per
food item to be calculated by the formula,
Calories = 4×Carbohydrates in grams + 4×Protein in grams + 9×Fat in grams.
While this equation is useful it is a little cumbersome to work with so let’s exercise our
brains and use a little more sophisticated but simplifying notation. Let Ni denote the
amount of nutrient i measured in grams. So, NC = Carbohydrates in grams,
NP = Protein in grams, and NF = Carbohydrates in grams. Using this shorthand notation
(aka known as variable notation) rewrite the equation as
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(1) 4 4 9 C PCals N N N= × + × + × F
FN
.
There are two important facts related to this equation to remember.
1. If we know the amount of carbohydrates (NC), fats (NF), and protein (NP) in a food
item we can calculate the amount of energy or calories (cals) in the food item.
For example, if a food item has 40 grams of carbohydrates (NC = 40), 30 grams of protein
(NP = 30), and 20 grams of fat (NF = 20) then substituting into equation (1) we get 460 =
4 × 40 + 4 × 30 + 9 × 20.
2. There are substitution possibilities between nutrients holding calories constant. Stated
alternatively, there are tradeoffs between carbohydrates, fats, and protein for the same
energy level.
To see this lets rewrite equation (1) by solving for one of the nutrients (i.e., place one of
the nutrients on the left side of the equal sign). Suppose we solve equation (1) for NC.
Recall from basic algebra we first subtract from both sides 4 9PN× + × , which gives
4 9 4P FCals N N N− × − × = × .C Now divide through both sides by 4 to yield
9 4 4C P
CalsN N= − − FN
FN
. Writing this in decimal form gives
(2) .25 2.25C PN Cals N= × − − × .
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Equation (2) is useful for two things. First, if you tell me the amount of calories, protein,
and fat in a food item, I can use equation (2) to determine the amount of carbohydrates in
the item. For example, suppose Cals = 200, NP = 20, and NF = 10, then from using (2)
we know NC = 7.5. Second, we can use equation (2) to determine the tradeoff between
carbohydrates and either calories, protein, or fat, holding all else constant. For example,
equation (2) tells us that if we want to keep the calories and fat constant, if we increase
protein by one gram we must decrease carbohydrates by one gram. This should make
sense because carbohydrates and protein each have 4 grams of energy. What about the
tradeoff between carbohydrates and fat? Again, assuming calories and protein are held
constant, then if we increase the fat content by one unit we must decrease carbohydrates
by 2.25 grams. Can you derive the equations for Np and NF comparable to equation (2).
Consider table 3 below, which gives the energy yielding macronutrients for several
items.
Table 3. Selected Food items, Macronutrients, and Calories
Food Item Quantity Weight(g)
Carb (g)
Prot (g)
Fat (g)
Energy (cals)
Big Mac Hamburger 1 item 216 47 24 34 590 Raw carrots 1 c. 122 12 2 0 56 Coca‐Cola Classic 12 oz. 360 41 0 0 164 Boston Market Half Chicken, w/ skin 1 item
277 4 70 33 593
Using equation (1), the total number of calories for the Big Mac Hamburger is 590 =
4×47 + 4×24 + 9×34 and others are calculated the same way. Note that the Boston
Market Half Chicken with skin has basically the same number of calories as the Big Mac
but for different reason. While the Big Mac has 47 grams of carbohydrates, the chicken
has only 4. Alternatively, the chicken has 70 grams of protein whereas the Big Mac has
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24. This example demonstrates the second point: equivalent calories do not imply
equivalent macronutrient levels.
One problem with just looking at calories is the total number of grams (in weight) can
differ from one food item to another. For a simple example, two Big Macs would weigh
432 grams and have twice as many of all nutrients and grams. Alternatively, compare the
Big Mac to the Raw Carrots. The Big Mac weighs 216 grams whereas the Raw Carrots
weigh 122 grams. More informative measures of nutrients and energy can be created by
“normalizing” the measures, where normalize just means place on some common scale.
There are several different normalizations that are informative. For example we could
look at the contribution to total calories of each energy yielding nutrient by simply
dividing both sides of equation (1) by total calories and multiplying by 100 to yield
4 4 9(2) 100 100
4 4 4100 100 100 .
=
C P F
C P F
N N NCalories
N N NCalories Calories Calories
× + × + ×= ×
× × ×⎛ ⎞ ⎛ ⎞ ⎛ ⎞× + × + ×⎜ ⎟ ⎜ ⎟ ⎜ ⎟⎝ ⎠ ⎝ ⎠ ⎝ ⎠
Each component of equation (2) is just a percentage so let’s define each component as the
nutrient density. That is nutrient density is the contribution to total calories provided by
the calories of an individual nutrient or for these nutrients in mathematical terms
4(3) 100 :CC
N ND Nutrient Density of CarbohydratesCals×
= ×
4(4) 100 :PP
N ND Nutrient Density of ProteinCals×
= ×
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9(5) 100 :FF
N ND Nutrient Density of FatsCals×
= ×
For example, the carbohydrate nutrient density scores for the above items are Big Mac
NDC (Big Mac)= 31.86 = [(4×47)/590]×100, NDC (Raw Carrots) = 85.71 = [(4×12)/56]×100,
NDC (Coca-Cola Classic) = 100 =[(4×41)/164]×100, and the NDC (Half Chicken) = 2.69 =
[(4×4)/593]×100. So on a per calories basis, the Coca-Cola classic has the highest
nutrient density for carbohydrates. The other nutrient density scores would be calculated
similarly. Note using this notation, equation (2) can be written more simply as
100 .C PND ND ND= + + F
An alternative normalization that is often encountered is energy density. Energy
density is defined as the ratio of total calories to total weight in grams or mathematically
(6) :fCalories in grams ED Energy Density of Food fWeight in grams
=
The energy densities for the above items are EDBig Mac = 2.73 = 590/216, EDRaw Carrots =
.46 = 56/122, ED Coca-Cola Classic = .45 = 164/360, and the ED Half Chicken = 2.14 = 593/277.
On a per gram basis the Big Mac and Half Chicken have an energy density about six
times greater than the raw carrots and the 12 ounce Coca-Cola. Table 4 summarizes the
nutrient and energy densities for the individual foods.
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Table 4. Selected Food items, Nutrient Densities and Energy Densities
Food Item Quantity NDC NDP NDF ED Big Mac Hamburger 1 item 31.86 16.27 51.86 2.73 Raw carrots 1 c. 85.71 14.28 0 0.46 Coca‐Cola Classic 12 oz. 100 0 0 0.45 Boston Market Half Chicken, w/ skin 1 item 2.69 47.21 50.084 2.14
THINK BREAK!!!!!!:
Using the data in table 5 answer the following questions.
Table 5. Nutrient Characteristics of a Chick Fil-A Meal
Food Item Quantity Weight(g)
Carb (g)
Prot (g)
Fat (g)
Chick Fil‐A Chicken Deluxe Sandwich 1 item
208 39 28 16
Waffle potato fries (small) 1 item 85 37 3 5 Coca‐Cola Classic 12 oz. 360 41 0 0
1. What is the total energy for each food item?
2. What is the energy density for each food item?
3. What is the nutrient density for carbohydrates for each item?
4. What is the nutrient density for protein for each item?
5. What is the nutrient density for fat for each item?
Meals: Nutrient and Energy Characteristics
Note from tables 3 and 4 the focus is on the characteristics of the individual food items.
However, using the information in table 3 we can also make similar calculations for a
meal.
Suppose Meal 1 consists of a Big Mac, 1 cup of raw carrots, and a 12 ounce Coca-
Cola and Meal 2 consists of the Half-Chicken, 1 cup of raw carrots, and a 12 ounce Coca-
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Cola. If we sum the appropriate numbers in the columns then we obtain the nutrition
characteristics of the meal as shown in table 6. For example, for Meal 1 the total weight
is 698 g = 216 g + 122 g + 360 g and the total carbohydrates is 100 g = 47 g + 12 g + 41
g. Table 6 gives the total weight, total nutrient contents, and energy for each meal.
Table 6. Nutritional Characteristics of Meals
Meal Weight(g)
Carb
(g) Prot (g)
Fat (g)
Energy (cals)
Meal 1 (Big Mac, Carrots, Coke)
698
100
26
34
810
Meal 2 (Chicken, Carrots, Coke)
759
57
72
33
813
Though the total calories are comparable from these two meals the distribution of calories
stemming from the different macronutrients are very different. The main difference is
between carbohydrates and protein. Meal 1 has about twice as many carbohydrate grams
and about a third of the protein grams as Meal 2.
As with the individual foods we can also calculate the nutrient and energy densities.
By definition the nutrient density is the ratio of the nutrient in grams to the total energy in
grams. For Meal 1 the formula for carbohydrates is then
( )1
4 47 12 41100
810
49.4 : 1
C MealND
Nutrient Density of Carbohydrates in Meal
× + += ×
=
The other nutrient densities for Meal 1 (or Meal 2) can be calculated the same way.
Note the general formulas for the nutrient density for carbohydrates, protein, and fat for
Meal 1 are then
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Nutrient Density for Carbohydrates Meal 1
( )1 2 31
1
4(7) 100C food item C food item C food item
C MealMeal
N N NND
Cals× + +
= ×
Nutrient Density for Protein Meal 1
( )1 2 31
1
4(8) 100P food item P food item P food item
P MealMeal
N N NND
Cals× + +
= ×
Nutrient Density for Fats Meal 1
( )1 2 31
1
9(9) 100F food item F food item F food item
F MealMeal
N N NND
Cals× + +
= ×
Obviously we could do the same thing for Meal 2.
What about the energy density of the meals? No Problem. Recall the definition of
energy density is the ratio of total calories to total weight in grams. For Meal 1 this
would be
1590 56 164 1.16
698MealED + += =
and for Meal 2
256 164 593 1.07.
759MealED + += =
The general formula for the energy density of a meal is then
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1 2 3(10) : 1,2food item food item food itemMeal i
Meal i
Cals + Cals +Cals ED i
Weight Grams= =
Table 7 gives the nutrient and energy densities for the two meals.
Table 7. Nutrient and Energy Densities of Meals Meal NDC NDP NDF ED Meal 1 (Big Mac, Carrots, Coke)
49.4
12.8
37.8
1.16
Meal 2 (Chicken, Carrots, Coke)
28.0
35.4
36.5
1.07
Meal 1 is more dense in carbohydrates than Meal 2, but Meal 2 is more protein dense
than Meal 1. Meal 1 is slightly more energy dense than Meal 2.
WARNING!!!:
• The nutrient density of a meal is not equal to the sum of the individual food
item’s nutrient densities in the meal.
• The energy density of a meal is not equal to the sum of the individual food
item energy densities.
Note you cannot just sum up the numbers in table 4 and get the numbers in table 7. Can
you explain why?
THINK BREAK!!!!!!:
Using the data from table 5 on the Chick Fil-A meal (repeated below) to answer the
following questions.
Table 5. Nutrient Characteristics of a Chick Fil-A Meal
Food Item Quantity Weight(g)
Carb (g)
Prot (g)
Fat (g)
Chick Fil‐A Chicken Deluxe Sandwich 1 item
208 39 28 16
Waffle potato fries (small) 1 item 85 37 3 5 Coca‐Cola Classic 12 oz. 360 41 0 0
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Assume the Chick Fil-A Meal is all three items:
1. What is the total energy for the meal?
2. What is the energy density for the meal?
3. What is the nutrient density for carbohydrates for the meal?
4. What is the nutrient density for protein for the meal?
5. What is the nutrient density for fat for the meal?
3. What Constitutes a Nutritious Diet?
A nutritious diet is considered to have five general characteristics:
1. Adequacy – Enough nutrients, fiber, and energy to sustain normal function.
2. Balance – Not skewed toward one nutrient or food type.
3. Calorie Control – Not less or more than required.
4. Moderation – No excess fat, salt, sugar, or other unwanted (WHAT??).
5. Variety – intake differs from one day to the next.
These five general characteristics are perhaps helpful if you already know a lot about
nutrition, but for the typical person these five characteristics do not provide enough detail
and specificity to be of much use in actually choosing specific foods. To help in
choosing specific nutrients and foods nutritionists have developed a set of “nutrient
recommendations.”
Nutrient recommendations are a set of “yardsticks”, or standards for measuring a
“healthy” person’s energy and nutrient intake. Note this idea of “nutrient
recommendations” is in economic terminology a normative concept, in the sense that it is
saying what “should” be done to obtain optimal health. The explicit goal of these
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recommendations is good health, not what necessarily taste the best, is cheapest, or is
most convenient.
Dietary reference intakes (DRIs) serve as the foundation for recommendations related
to nutrient intake. The National Academy of Sciences’ Institute of Medicine has a Food
and Nutrition Board and from that board there is a DRI committee composed of nutrition
experts that determine DRI variables and values. The Dietary Reference Intakes (DRI)
are four variables or measurements of the nutrient intakes of healthy people in the United
States and Canada. The four variables are:
1. Estimated Averages Requirements (EARS)
2. Recommended Daily Allowances (RDA)
3. Adequate Intakes (AI)
4. Tolerance Upper Intake Levels (UL)
DRIs are determined for all of the vitamins and minerals, as well as carbohydrates, fiber,
lipids, protein, water, and energy.
How are these four variables defined?
Estimated Average Requirement (EAR) – The average daily intake level for a nutrient
which meets the needs of 50 percent of the population in particular life stages and gender
groups.
Recommended Daily Allowances (RDA) – The average daily nutrient intake level that
meets the needs of nearly all (97% to 98%) of healthy people in a particular life stage and
gender group.
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Adequate Intake (AI) – The recommended average daily nutrient intake levels based on
intakes of healthy people (observed or experimentally derived) in a particular life stage
and gender group and assumed to be adequate.
Tolerable Upper Intake Levels (UL) – The highest average daily nutrient intake level
that is likely to pose no risk of toxicity to almost all healthy individuals of a particular life
stage and gender group.
The following facts help put the DRI recommendations in perspective:
• The values are based on scientific evidence to the greatest extent possible and
are periodically updated.
• Values are based on concepts of probability and risk: low probability of
deficiency and no risk of toxicity.
• Values are recommended for optimal intakes, not minimum requirements.
They include a large safety margin.
• The values are set in reference to certain indicators of nutrient adequacy, such
as blood nutrient concentrations, normal growth, and reduction of certain chronic
diseases.
• The values reflect daily intakes to be achieved over time, on average.
• Recommendations apply to a healthy person only.
All of these recommendations are based on different aspects of the empirical distribution
of nutrient intakes. To understand the differences in these measures consider a simple
example of 10 people as given in table 8.
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Table 8. Sample Daily Intake of Protein Individual Average Daily Intake (g)
1 10 2 15 3 28 4 36 5 45 6 48 7 54 8 60 9 64
10 72 The EAR for this data would be 45 g as 50% of the individuals consume this amount of
protein or less. If the RDA was defined to meet the needs of 90% of the population then
the RDA for this sample would be 64 g as 90% of the individuals consume this amount or
less. However, because the actually RDA percentage is between 97% and 98%, for this
sample the actual RDA would be somewhere between 64 g and 72 g. The AI and UL
would represent other points within this distribution of intakes. More generally we can
think of there being a distribution of average daily nutrient intakes such as,
XDRA
.02 to .03 of distribution
EAR
It is important to remember that all of these measures and recommendations are age
and gender specific, meaning there are different values for different ages and males and
females. The DRI committee publishes tables of all the DRIs and can be found online at
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the Food and Information Nutrition Center (FINC) http://www.nal.usda.gov/fnic/ and
following the link for Dietary Guidelines. Table 9 below gives an example of what can
be found there in terms of RDAs/AIs for the energy yielding macronutrients, two
vitamins and two minerals for the age range covering most in this class. Of course the
actual tables have the DRIs for all the micronutrients (i.e., 14 vitamins and 15 minerals).
Table 9. Sample of RDAs or AIsa
RDAs or AIs Male 19 - 30 y Female19 - 30 y
Carbohydrates (g/d) 130 130 Protein (g/d) 56 46 Fat (g/d) ND ND Vitamin C (mg/d) 90 75 Vitamin E (mg/d) 15 15 Calcium (mg/d) 1000 1000 Iron (mg/d) 8 18 a. RDAs in bold and AI non-bold. ND = Not determinable due to lack of data of adverse effects with lack of ability to handle excess amounts. Source: National Academy of Sciences. Institute of Medicine. Food and Nutrition Board.
While useful the DRI measures are not expressed on a normalized scale that allows
for ease in comparison of one or more nutrients and foods. One such measure is the
Acceptable Macronutrient Distribution Range (AMDR). The Acceptable
Macronutrient Distribution Range (AMDR) is a nutrient density range that is
sufficient to provide adequate total energy and nutrients while reducing the risk of
chronic disease.
With these measures, the DRI committee has four main goals:
1. Set recommended intake values – Recommended intake values are based on
either RDAs or AIs. RDA is based on experimental and reliable observations. AI
is based on some guess work. If there is insufficient evidence for a RDA, an AI is
given instead.
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2. Facilitate Nutrition Research and Policy – The EARs are used to establish
guidelines to be used in research and policy work, and form the basis of the
RDAs.
3. Establishing Safety Guidelines – The ULs provide upper limits before toxicity
is expected to occur.
4. Preventing Chronic Diseases – The following AMDR provide adequate
energy and adequate nutrients for adults 20–35 while reducing the risk of chronic
diseases:
• 45% - 65% energy from carbohydrates
• 20% - 35% energy from fat
• 10% - 35% energy from protein
B. Foods and Nutrition
Ok, so we have some good background now on nutrients but people eat foods, which
leads to a natural question
How do we calculate the amount of nutrients in a diet composed of various foods?
Don’t let the word “calculate’ scare you. The calculations are not that hard but it does
involve some math. Just read slowly. Think of it this way. Foods are bundles of
nutrients or a delivery device for nutrients. We have already seen this in the previous
section where we talked about the nutrient content of different food items. For example,
from table 3 we know that there are 47 g of carbohydrates in a Big Mac Hamburger that
weighs 216 g. This means that .218 = 47/216 of the total grams in a Big Mac Hamburger
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are associated with carbohydrates or the carbohydrate conversion factor is .218 for Big
Mac Hamburger. The carbohydrate conversion factor for Raw Carrots is .0984 = 12/122
and for a Coca-Cola is .114 = 41/360. The other nutrient conversion factors can be
similarly determined.
Let us then define the nutrient conversion factor to be the amount by which you
multiply the quantity of food to determine the amount of that nutrient. This implies that if
we know the nutrients conversion factors for the different foods in a meal then we can
calculate the total nutrient intake from those foods. For example suppose we want to
know the total amount of carbohydrates in Meal 1 (1 Big Mac, 1 c raw carrots, and 1 12
ounce Coke) and we know the conversion factors for carbohydrates are .217, .098, and
.11 for these items in the meal. The total carbohydrates for Meal 1 is then
100 = .2176×216 + .0984×122 + .114×360.
(Aside: Note this is the same as reported in table 5 as it should be. Do you know why?).
Calculating the total amount of nutrients from a collection of foods is such a critical
part of the discipline of nutrition that we need to understand the more general formula.
Let the variable F1 denote the quantity (in grams) of food item one, F2 denote the
quantity (in grams) of food item two, F3 denote the quantity (in grams) of food item
three, etc, or more generally Fi where i is just an indexing mechanism and j = 1,2,…, K
so there are K foods. Furthermore let α11 be the nutrient conversion factor for nutrient
one in food one, α12 be the nutrient conversion factor for nutrient one in food two, α13 be
the nutrient conversion factor for nutrient one in food three, etc. So the general formula
for nutrient one is then
1 11 1 12 2 1(11) . . . K KN F F Fα α α= + + +
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where N1 just stands for the quantity of nutrient one (in grams).
Huh? Don’t panic. Just keep reading slowly. Ok, so for the above example let the
first food item be the Big Mac (so F1 = 216), the second food item be the Raw Carrots (so
F2 = 122) and the Coca-Cola the third food item (so F3 = 360). Now let the first nutrient
be carbohydrates, so the corresponding nutrient conversion factors are for the Big Mac
(α11 = .2176), for the Raw Carrots (so α12 = .0984) and for the Coca-Cola the third food
item (so α13 = .114). Substituting these values into equation (11) gives the value of 100
carbohydrates for Meal 1.
Equation (11) is the formula for nutrient one, but this formula applies to other
nutrients as well by just relabeling the nutrient number. So the general formula is then
1 1 2 2(12) . . . 1,2,...,i i i iK KN F F F i Jα α α= + + + =
where there are J nutrients. Note the i subscript on the nutrient conversion factors, so the
nutrient conversion factors differ by nutrient and food item. Later we will write this
relationship between food and nutrients as Ni =N(F1, F2,…, FK), which is just a shorthand
and more general way of saying the level of a nutrient depends on or is a function of the
amount of foods consumed. This notation is known as function notation and we will
discuss it in more detail at the beginning of the economics section.
THINK BREAK!!!!!!:
Below are the nutrient conversion ratios for one slice of Meat Lovers Pizza Hand Tossed
and a 16 oz. serving of lemonade.
Table 10. Nutrient Conversion Factors Food Item Quantity Weight Carb Prot Fat Meat Lovers Pizza (Hand Tossed) 1 slice 125 .13 .24 .12 Lemonade 16 oz. 483 .16 .002 0
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If these two items are consumed together….
1. How many grams of carbohydrates are there?
2. How many grams of protein are there?
3. How many grams of fat are there?
Is your head starting to hurt yet from all these calculations and symbols flying
around? If so you are not alone. Though we have just skimmed the surface of nutrients
and nutrient recommendations it should be clear that there is a major limitation associated
with basing diet recommendations on nutrient intake. Individuals do not choose and
consume nutrients. Individuals choose and consume food items. By basing nutrient
recommendations solely on nutrients the consumer implicitly must be able to translate
from the food dimension to the nutrient dimension with ease. What does this mean? Well
there are 3 energy yielding macronutrients, 14 vitamins, and over 15 minerals considered
in defining a nutritious diet. Consequently, at a minimum there are 42 equations such as
equation (12) or more succinctly J > 42. In addition, if there are about 30,000 food items
in a typical food store then the K in equation (12) is potentially extremely large and this is
not even considering the other measures such as EARs, DRAs, nutrient density, energy
density that are relevant for a healthy diet. The amount of mental capital required to keep
track of all this information much less process it is overwhelming and requires a great
deal of nutrition knowledge that most individuals do not posses.3 Basing diet
recommendations on nutrients implicitly assumes the consumer has the knowledge and
3 Research in psychology has shown that humans can process at most about three variables at a time. For example See Halford, Wilson, and Phillips “Processing capacity defined by relational complexity: Implications for comparative, developmental, and cognitive psychology.” Behavioral and Brain Sciences (1998): 21, 803-865.
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computational capacity to convert different food items in to their nutrients components
and then compare those foods based on their nutrient quality. This is a rather unrealistic
expectation. This problem is well recognized in nutrition. As Mark B. McClellan,
Commissioner of the Food and Drug Administration (FDA) in 2003, has stated
People shouldn't need a calculator or an advanced degree in math or nutrition to calculate what makes a healthy diet. So we have to find a way to make the key information we require to be placed on individual food products easier for consumers to understand and use from the standpoint of what constitutes a healthy meal and a healthy diet. Right now, we communicate some very useful information about the nutritional value of individual foods, and we provide some help in thinking about how foods can contribute to a healthy diet. But combining foods into a healthy diet is still too complicated. Instead of doing the math, consumers often do simple substitutions, such as trading off a low-calorie cola with a high-calorie dessert. We need to find better, simpler ways to help consumers understand the nutritional value of entire diets. (M. B. McClelland, Speech given at Harvard School of Public Health 2003).
Because of these computational difficulties and limitations nutrition recommendations
are usually presented in terms of foods or groups of foods.
Food Classifications and Guidelines
Food is any substance that the body can take in and assimilate that will enable it to stay
alive and grow. This definition is simple enough but not very useful because there are so
many items that satisfy this definition. Any time a definition of a group of items is very
broad it is common to further partition the groups into other categories and so it is with
food. Here are some of the most common food categories or types.
Basic Foods – Milk and milk products, meats and similar foods such as fish and poultry,
vegetables, including dried beans and peas; fruits and grains. Also called whole foods.
Enriched/Fortified Foods – Foods to which nutrients have been added.
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Fast Foods – Restaurant food that is available within minutes of ordering.
Food-at-Home – Food prepared at home.
Food-Away-From-Home – Food prepared at some other location than a home.
Functional Foods – A misleading term to define a group of foods known to possess
nutrients or non-nutrients that might lend protection against diseases.
Medical Foods – Foods specially manufactured for use by people with medical disorders
and prescribed by physicians.
Natural Foods – No legal definition, but is often used to imply wholesomeness.
Nutraceutical Foods – A term with no legal or scientific meaning that refers to foods
claimed to have medicinal effects.
Organic Foods – Foods grown without synthetic pesticides.
Partitioned Foods – Foods composed of parts of whole foods, such as butter (from
milk), sugar (from beets), or corn oil (from corn)
Pre-prepared Foods –Foods have some minimal level of processing that can be used in
combinations with other foods.
Processed Foods – Foods subject to any process, such as milling, alteration of texture,
addition of additives, cooking, or others.
Staple Food – Food used frequently or daily (e.g. rice in Asia).
Clearly these classification schemes are not mutually exclusive. Many food items
could be classified under several types. For example, the McDonald’s hamburger is fast
food, food-away-from, and is certainly a processed food. Milk is certainly a basic food,
but it is also a natural food and may also be an organic food or in some cultures a staple
food. The general point is that there are numerous ways to classify foods and different
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classification schemes will be based on some common characteristics of the foods in that
category.
C. Nutrient and Food Recommendations
In this section we discuss nutrient and food recommendations. Most of these stem from
the Dietary Guidelines for Americans (DGA).4 Every 5-years the Dietary Guidelines
Advisory Committee (DGAC), which is appointed by the Secretaries of the U.S.
Department of Health and Human Services (HHS) and the U.S. Department of
Agriculture (USDA) review the most recent scientific information on nutrition and
published what is known as the DGAC Report
(http://www.health.gov/dietaryguidelines/dga2005/ report/). The report is a scientific
analysis and is not intended for distribution to the general public. However, from this
report the HHS and USDA jointly develop the Dietary Guidelines for Americans (DGA).
The purpose of the DGA is to use the current state-of-the art knowledge on nutrients and
foods to develop recommendations for healthful eating patterns that can be adopted by
the public.
A key component of the DGA is the grouping of foods into seven groups. These
seven basic food groups are
1. Fruits
2. Vegetables 4 The description of the Dietary Guidelines For Americans 2005 draws heavily from the Executive Summary from the Dietary Guidelines For Americans 2005, which can be found at http://www.health.gov/dietaryguidelines.
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3. Grains
4. Meat, Poultry, Fish, Dried Peas and Beans, Eggs, Nuts
5. Milk, Yogurt, Cheese
6. Oils
7. Solid Fats and Added Sugars
The DGA gives a rather extensive list of the foods falling into these food groups.
These food groups play a prominent role in the recommendations and several
recommendations are stated in terms of consumption of these food groups. The key
recommendations coming from the DGA are grouped into nine inter-related focus areas.
Table 11 gives a summary of the key recommendations for the general population.
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Table 11. Key Recommendations for General Population from the Dietary Guidelines for Americans 2005.
1. ADEQUATE NUTRIENTS WITHIN CALORIE NEEDS
• Consume a variety of nutrient-dense foods and beverages within and among the basic food groups. • Choose foods that limit the intake of saturated and trans fats, cholesterol, added sugars, salt, and alcohol. • Adopt a balanced eating pattern across foods
2. FATS
• Consume less than 10 percent of calories from saturated fatty acids and less than 300 mg/day of cholesterol, and keep trans fatty acid consumption as low as possible. • Keep total fat intake between 20 to 35 percent of calories, with most fats coming from sources of polyunsaturated and monounsaturated fatty acids, such as fish, nuts, and vegetable oils. • When selecting and preparing meat, poultry, dry beans, and milk or milk products, make choices that are lean, low-fat, or fat-free. • Limit intake of fats and oils high in saturated and/or trans fatty acids, and choose
products low in such fats and oils. 3. CARBOHYDRATES
• Choose fiber-rich fruits, vegetables, and whole grains often. • Choose and prepare foods and beverages with little added sugars or caloric sweeteners, such as amounts suggested by the USDA Food Guide and the DASH Eating Plan. • Reduce the incidence of dental caries by practicing good oral hygiene and consuming sugar- and starch-containing foods and beverages less frequently.
4. SODIUM AND POTASSIUM
• Consume less than 2,300 mg (approximately 1 teaspoon of salt) of sodium per day. • Choose and prepare foods with little salt. At the same time, consume potassium-rich foods, such as fruits and vegetables.
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Table 11. Con’t 5. FOOD GROUPS TO ENCOURAGE
• Consume a sufficient amount of fruits and vegetables while staying within energy needs. Two cups of fruit and 2½ cups of vegetables per day are recommended for a reference 2,000-calorie intake, with higher or lower amounts depending on the calorie level. • Choose a variety of fruits and vegetables each day. In particular, select from all five vegetable subgroups (dark green, orange, legumes, starchy vegetables, and other vegetables) several times a week. • Consume 3 or more ounce-equivalents of whole-grain products per day, with the rest of the recommended grains coming from enriched or whole-grain products. In general, at least half the grains should come from whole grains. • Consume 3 cups per day of fat-free or low-fat milk or equivalent milk products.
6. WEIGHT MANAGEMENT
• Balance calories from foods and beverages with calories expended. • To prevent gradual weight gain over time, make small decreases in food and beverage calories and increase physical activity.
7. PHYSICAL ACTIVITY
• Engage in regular physical activity and reduce sedentary activities. • To reduce the risk of chronic disease in adulthood: Engage in at least 30 minutes
of moderate-intensity physical activity, above usual activity most days of the week.
• To help manage body weight in adulthood: Engage in approximately 60 minutes of moderate- to vigorous- intensity activity on most days of the week while not exceeding caloric intake requirements. • To sustain weight loss in adulthood: Participate in at least 60 to 90 minutes of
daily moderate-intensity physical activity while not exceeding caloric intake requirements. Some people may need to consult with a healthcare provider before participating in this level of activity.
• Achieve physical fitness by including cardiovascular conditioning, stretching exercises for flexibility, and resistance exercises or calisthenics for muscle strength and endurance.
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Table 11. Con’t 8. ALCOHOLIC BEVERAGES
• Those who choose to drink alcoholic beverages should do so sensibly and in moderation—defined as the consumption of up to one drink per day for women and up to two drinks per day for men. • Alcoholic beverages should not be consumed by some individuals, including those who cannot restrict their alcohol intake, women of childbearing age who may become pregnant, pregnant and lactating women, children and adolescents, individuals taking medications that can interact with alcohol, and those with specific medical conditions. • Alcoholic beverages should be avoided by individuals engaging in activities that require attention, skill, or coordination, such as driving or operating machinery.
9. FOOD SAFETY
• To avoid microbial food borne illness: Clean hands, food contact surfaces, and fruits and vegetables. Meat and poultry should not be washed or rinsed. • Separate raw, cooked, and ready-to-eat foods while shopping, preparing, or
storing foods. • Cook foods to a safe temperature to kill microorganisms. • Chill (refrigerate) perishable food promptly and defrost foods properly. • Avoid raw (unpasteurized) milk or any products made from unpasteurized milk,
raw or partially cooked eggs or foods containing raw eggs, raw or undercooked meat and poultry, unpasteurized juices, and raw sprouts.
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The numbering in table 11 does not indicate any type of priority ordering and all nine
recommendations are equally important. It also should be recognized that this is just a
summary of the key recommendations as the DGA has a full chapter devoted to each one
of these nine focus areas, so there is a lot more detail in each focus area.
So What Does the DGA Mean for a Diet?
While the DGA is certainly a step in the right direction in terms of translating nutrient
recommendations into food recommendations, it is still “informationally dense” and not
in a ‘digestible’ form to the consumer. Diet planning is designed to connect the
recommendations from nutrition science with the food people consume and this involves
several educational tools. One such tool is the food group plan. The food group plan is
a diet planning tool provided by USDA that sorts foods into groups based on their
nutrient content and then specifies that people should eat a certain minimum number of
servings for foods from each group. The USDA food group plan is known as the USDA
Food Guide and table 12 gives a sample from that table.
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Table 12. Sample USDA Food Guide Table Daily/Weekly Servingsa
Food Group Calories 1600 2000 2400
Fruits 1.5 c (4 srv) 2 c (4 srv) 2 c (4 srv) Vegetables 2 c (4 srv) 2.5 c (5 srv) 3 c (6 srv) Dark Green 2 c/wk 3 c/wk 3 c/wk Orange 1.5 c/wk 2 c/wk 2 c/wk Legumes 2.5 c/wk 3 c/wk 3 c/wk Starchy 2.5 c/wk 3 c/wk 6 c/wk Other 5.5 c/wk 6.5 c/wk 7 c/wk Grains 5 oz-eq 6 oz-eq 8 oz-eq Whole 3 3 4 Other 2 3 4 Lean Meat and Beans 5 oz-eq 5.5 oz-eq 6.5 oz-eq Milk 3 c 3 c 3 c Oils 22 g 27 g 31 g Discretionary Calorie Allowance 182 267 362 a Taken from the USDA Dietary Guidelines for Americans 2005. The DGA provides a rather extensive list of the sub-food types (e.g., Dark Green vegetables) from which a consumer can choose.
The calorie columns indicate the amount of calories consumed. So for example if the
recommended energy intake for someone is 2000 calories per day then if they consume
about 2 c of fruits, 2.5 c of vegetables, 6 ounces of grain, 5.5 ounces of lean meat or
beans, 3 c of milk (products), and 27 g of oil products per day then they will generally
meet the nutritional recommendations in terms of nutrients. One should realize that there
is still a great deal of substitutability within these food groups and this guide is not as
rigid as it may seem at first. Note at the bottom of this table is a row called Discretionary
Calorie Allowance. The Discretionary Calorie Allowance (DCA) is the balance of
calories remaining in a person’s energy allowance after accounting for the number of
calories needed to meet recommended nutrient intakes through consumption of nutrient
dense food. Simply stated, after you consume the amounts given in the table, the DCA
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indicates how much you have to play with. Alternatively, the caloric value of all the
items in the portions given must be for the 2000 calorie diet 1733 = 2000 – 267.
Though the Food Guide is certainly more user friendly than recommendations
expressed in terms of nutrients, USDA has developed the MyPyramid as an educational
tool to make implementing the Food Guide even easier.
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MyPyramid
MyPyramid is an educational tool developed by the USDA to help individuals follow the
Food Guide. The general idea behind MyPyramid is to give a quick, visual
representation of what foods should be consumed. Figure 1 below shows the MyPyramid
diagram.
Figure 1. MyPyramid.
The design of the MyPyramid is intended to reflect the major components of the Food
Guide. The six different colors represent the different food groups. Proportionality of
these food groups is represented by the width of each color band, so for example grains,
vegetables and fruits should constitute over half of the diet. Because all food groups are
included variety is captured as well. The steps are designed to reflect the importance of
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activity. Moderation is supposedly reflected by the narrowing of each food group from
top to bottom. The wider base stands for foods with little or no solid fats or added sugars.
The MyPyramid is actually a group of 12 different MyPyramids that are tailored to
specific energy requirements and activity levels.
There are numerous resources available to consumers related to the MyPyramid
concept that are targeted at different media outlets, including public service
announcements, podcasts, posters, internet video clips, and WebPages. The webpage
www.mypyramid.gov has numerous links that are based on the MyPyramid concept that
provide information and other tools for helping the consumer follow the Food Guide. For
example, the link, MyPyramid Menu Planner,
(http://www.mypyramidtracker.gov/planner/launchPage.aspx)
allows one to enter personal information related to weight and height and activity level
and then enter different food choices and see how those choices compare to the Food
Guide recommendations. Alternatively one can use the MyPyramid Tracker
(http://www.mypyramidtracker.gov) to assess dietary and physical activity. For example,
there is a Food Calories/Energy balance feature that will calculate your energy balance by
subtracting the energy you expend from physical activity from your food caloric intake.
While the MyPyramid is a useful tool, the mere fact that it condenses a great deal of
information into a simple pyramid it may come as no surprise that it has some limitations.
Here are some of the main ones as pointed out by Marion Nestle in Food Politics:
Does not distinguish the health impact of total fat from the effects of
saturated, monosaturated, polyunsaturated, and trans-saturated fatty acids.
Does not emphasize the fact that there are no “good” or “bad” foods.
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Does not emphasize whole, minimally processed grains compared to refined
grains.
Does not separate beans (a vegetable) from meat.
Does not distinguish high-fat from low-fat meat and dairy products.
Does not guide educators and the public in placing commonly consumed
foods in appropriate groups.
Does not explain serving sizes adequately or consistently.
Convey the complexities of information about nutrition and health.
Does not distinguish serving recommendations that should be considered
upper limits (meat and high-fat dairy foods) from those that should be considered
lower limits (grain, fruit, and vegetable soups).
Though these are obvious limitations of the MYPyramid as it stands, there are two
other perhaps more important limitations. First, the MyPyramid only applies to food
groups. However, much food that is purchased is processed to some degree and does not
really fit into a food group. For example, what food group does a can of Campbell’s
Mushroom soup fall in to? Or even more processed, a Healthy Choice Zucchini
Lasagna? Second, and related to one, MyPyramid is a good general planning and
evaluation tool over several days, but it is not very useful when a consumer is standing in
the store trying to compare two different food items (e.g., Count Chocula versus Honey
Gone Nuts Granola). To address these problems requires that individual food items have
nutritional information on the label.
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Food Labels: Required Items Prior to 1990, there was no uniform standard for the type of information that could be
placed on a food label. Consequently, and as part of marketing efforts, many companies
made claims about their foods that were at a minimum misleading and in some cases just
false. The Nutrition Education and Labeling Act (NELA) of 1990 was passed in order to
address this problem. The NELA requires every food packaged to contain the following
information:
1. The common or usual name of the product.
2. The name and address of the manufacturer, packer, or distributor.
3. The net content in terms of weight, measure, or count.
4. Nutrient contents of the product (nutrition facts panel).
5. The ingredients in descending order of predominance by weight.
The actual content of the label will depend on the size of the product. For example a
cereal box might include all nutrients including vitamins and mineral, whereas a can of
tuna may contain an abbreviated listing of nutrients. A candy bar label may just have a
phone number for providing the information. Figure 2 shows a nutrition label for a box
of cookies.
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Figure 2. Cookies Food Label Example
Starting at the top of the label, the serving size is expressed in some common units, such
as number of cookies, but also in grams and then the servings per container. The
following information is all expressed in terms of nutrient content per serving. Total
calories (160) are given along with total calories from fat (60). The major macro and
micronutrients in the product are then listed in terms of grams and daily values. The
Daily Values (DVs) are daily nutrient standards expressed as a percent of a 2,000 calorie
diet. For this box of cookies total fat is 7.0g and this constitutes 10% of what the total
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amount of fat recommended for a daily caloric intake of 2000 calories. Total fat is
further broken down into saturated fat and trans fat. Cholesterol and sodium measures
are also given. Total fat, Cholesterol, and sodium should be consumed in limited
quantities and kept at a minimum. The general rule of thumb or quick guide is to look for
items where these DVs are 5% or less and 20% or more is considered high. The other
two energy yielding macro nutrients are given as well (Total carbohydrates and Protein).
The next section gives the key vitamins and minerals in the food item. In terms of a
quick guide, dietary fiber, Vitamin A, Vitamin C, Calcium, and Iron should have daily
values 20% or more. The bottom panel, or footnote, indicates that DVs are based on a
2000 calories per day diet. This footnote is the same for all food products. For some
products there will be additional information given in the footnote. This information lists
the guidelines or recommendations for the relevant nutrients for different caloric intake
levels. Note these numbers give the maximum amount that should be consumed of these
nutrients for this caloric intake for a given day across all foods. This is not the amount
that can be consumed from just this item, unless this is the only item you consume all
day. The DVs are actually calculated using these numbers along with the quantity of the
nutrients per serving given above. For example, the DV for Total Fat is
. The other DVs are calculated similarly or the general formula
for a nutrient DV is
10% (7 / 65 ) 100g g= ×
(13) 100ii
i
NDVRN
⎛ ⎞= ×⎜ ⎟⎝ ⎠
where Ni is as before, the nutrient quantity of nutrient i and RNi is the recommended
nutrient intake for nutrient i. Finally, below the Nutrition Facts panel are given the
ingredients in the item in descending order of weight contribution. For example, for
39
these cookies the ingredient list indicates that the largest portion of the weight is sugar,
followed by enriched wheat flower, then vegetable shortening, etc…
There are several points to keep in mind when considering the information on nutrient
levels:
There are going to be tradeoffs or substitutions to consider between the
different nutrients. For example, the quick guide indicates that these cookies are
high in fat (DVfat = 10%) but nonexistent in terms of Vitamin A (e.g., DVVitA =
0%).
All nutrient content information is based on a single serving but most
containers will have more than one serving. Consequently, the actual nutrient
intake and DVs will equal the number of servings consumed. For example, if the
container has two servings and you consume two servings then all values in the
nutrient label will be doubled.
Two similar products may contain different calorie levels making it difficult
to compare the nutrient content of one to the other without converting them to a
common serving size.
Not all nutrients will have both the quantity and DVs given on the label. This
is because the DRI committee could not form a conclusive opinion on the
numbers.
Food Labels: Optional Items The above food label information is required on all food items, but there are additional
optional items mainly related to additional nutrient claims and health claims. The
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Nutrient Claims are claims about nutrients that must meet some specified criteria.
These claims are broken down mainly in terms of calories and fat related items. Table 13
gives the criteria for different nutrient claims.
Table 13. Nutrient Claims and Their Meaning ENERGY TERMS (PER SERVING)
Low calorie - ≤ 40 calories
Reduced calorie - at least 25% lower in calories than a regular or reference food.
Calorie free - < 5 calories
FAT TERMS (MEAT AND POULTRY PRODUCTS)
Extra Lean (per serving) < 5 g fat + < 2 g (saturated and trans fat) + < 95 mg cholesterol
Lean (per serving) < 10 g fat + < 4.5 g (saturated and trans fat) + < 95 mg cholesterol
FAT TERMS (MAIN DISHES AND PREPARED MEALS)
Extra Lean (per serving) < 5 g fat + < 2 g (saturated and trans fat) + < 95 mg cholesterol
Lean (per serving) < 8 g fat + < 3.5 g (saturated and trans fat) + < 80 mg cholesterol
FAT AND CHOLESTEROL TERMS (ALL PRODUCTS)
Cholesterol Free (per serving) < 2 mg cholesterol + ≤ 2 g (saturated and trans fat)
Fat Free (per serving) < .5 g fat
Less Saturated Free (per serving)
at least 25% lower in calories than a regular or reference food.
Low Cholesterol (per serving) ≤ 20 mg + ≤ 2 g fat
Low fat (per serving) < 3 g fat
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Low saturated fat (per serving) ≤ 1 g saturated fat + < 0.5 g trans fat
Reduced or less cholesterol (per serving) ≥ 25% less cholesterol compared to reference food + ≤ 2 g saturated fat
Reduced Saturated Fat (per serving) ≥ 25% less saturated fat + reduced by more than 1 g saturated fat compared to reference food
Saturated Fat Free (per serving) < 0.5 g of trans fat+ < 0.5 g saturated fat
FIBER TERMS
High Fiber (per serving) > 5 g fiber + must satisfy the low fat definition or level of total fat must appear next to high fiber claim
Good Source of Fiber (per serving) 2.5 g to 4.9 g of fiber
More or Added Fiber (per serving) ≥ 2.5 g serving relative to reference food
SODIUM TERMS
Low Sodium (per serving) ≤ 140 mg
Reduced Sodium (per serving) ≥ 25% less sodium than reference food
Sodium Free (per serving) < 5 mg
Very Low Sodium (per serving) ≤ 35 mg
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OTHER TERMS
Free, Without, No, Zero (per serving) Zero or trivial amount
Calorie Free (per serving) < 5 calories
Sugar or Fat Free (per serving)
< .5 g
Fresh Raw, unprocessed, or minimally processed
Good Source (per serving) 10% to 19% of Daily Values
Healthy Low in fat, saturated fat, trans fat, cholesterol, and sodium and containing at least 10% of Daily Values for vitamin A, vitamin C, iron, calcium, protein, or fiber.
High In (per serving) 20% or more of Daily Values
Less, Fewer, Reduced ≥ 25% less of a nutrient or calories than reference food
More, Extra (per serving) ≥ 10% more than Daily Values in reference food
Light (per serving) - three possible meanings
1. 1/3 fewer calories or half the fat of the regular product 2. 1/2 sodium normally present 3. Light in color or texture.
These nutrient claims are designed to help “simplify” the nutrient information. Do you
think they do that?
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Health Claims are claims linking certain nutrients to health claims and must satisfy
criteria set by the FDA. Examples of health claims are statements such as “calcium and
reduced risk of osteoporosis” or “dietary fat and reduced risk of cancer.” The FDA has
four levels on their ‘report card’ health claims.
A – High level of confidence in health claim with significant scientific
agreement. No disclaimers.
B – Moderate level of confidence in health claims with supportive but not
conclusive evidence.
C – Low level of confidence in health claim with limited evidence that is not
conclusive.
D – Extremely Low level of confidence in health claim with little scientific
evidence supporting the claim.
While nutrient claims are rather precisely defined, health claims are much more tenuous
because the relationship between nutrition and health is obviously much more tenuous as
we will discuss in the next section.
D. Diet and Health
So far we have covered the relationship between nutrients and foods, and nutrition
recommendations and guidelines. Much of the motivation for developing nutrition or
diet guidelines is to reduce the onset of several chronic diseases. Indeed, as was
indicated in module I, four of the top 10 leading causes of death (e.g., heart disease,
cancer, strokes, and diabetes) are all known to be highly correlated with diet. It is
important to note that correlation is not causation. What we mean by correlation in this
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context is that while diet is one factor that can influence the onset of a disease, there are
certainly other factors as well. For example, other factors that may affect the onset of a
disease would be genetics, exercise, smoking, or environmental conditions such as
pollution or sanitation practices. These other factors can either attenuate or accentuate
the effects of a specific diet. For example, we all probably know a friend who seems to
be able to eat as much of anything they want and they seem to never gain any weight.
This person probably has a unique genetic makeup that tends to offset the negative
impacts of a poor high caloric diet. Alternatively, it is well established that a diet high in
fat may accentuate the chance of heart disease but a consistent vigorous exercise program
would tend to attenuate the effects of the high fat diet on the chance of developing heart
disease. The general point is that when we talk about the connection between diet and
health there is an implicit assumption that we are holding all other variables constant or
equal. This type of “holding all else constant or equal” reasoning is pervasive in science
and usually goes by the Latin name ceteris paribus, which means other things being
equal. So when someone says that a high fat diet increases the likelihood of heart disease
they are implicitly saying, more accurately, that a high fat diet increases the likelihood of
heart disease, ceteris paribus. While more technically correct, adding the ceteris paribus
phrase to every diet health claim becomes extremely repetitive and retentive and is
therefore often usually not included.
Because the relationship between diet and disease (or more generally health) is not
one-to-one, nutritionists and health professional usually refer to the different factors that
can affect the onset and level of a disease as risk factors. Risk factors are factors known
to be related to (or correlated with) diseases but not proven to be causal. To make sure
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we are on the same page we should probably define risk as well. If one goes to a
dictionary and looks up the word risk they will find something like, risk is exposure to
the chance of injury or loss. This is not the definition of risk we will use because it does
not distinguish between measureable risk and unmeasurable risk. There are chances of
loss that can be measured and there are chances of loss that we have no idea of how to
measure. For example, suppose we bet a dollar on a coin toss. You win if it turns up
heads and I win if it turns up tails. Assuming the coin is fair, we know you have a 50%
chance of loss or your risk of loss is 50%. Now contrast this with a dollar bet on Virginia
Tech changing its primary colors to orange and black within the next 5 years. There is
certainly a chance this could happen but there is no precedent or data for assigning a
number to this chance as in the coin toss case. To distinguish these two cases we will
reserve the term risk for cases where there is a quantifiable chance or probability of loss.
We will refer to a chance that is non-quantifiable as referring to uncertainty.5
The table 14 below list the major diet related risk factors for several chronic diseases.
As the table shows, several of the same dietary intake patterns are associated with
increasing the probability of several chronic diseases. For example, a diet high in fat,
saturated fat, and trans fats increases the probability of having all four of these chronic
diseases.
5 This important distinction between risk and uncertainty is based on the distinction made by Economist Frank Knight in his 1921 publication Risk, Uncertainty, and Profit. This distinction is to some extent one of available data and knowledge and will become more important in the economics section.
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Table 14. Diet Related Risk Factors with Some Chronic Diseases Chronic Diseases Risk Factors Atherosclerosis Hypertension Strokes Cancers Diet high in fat, saturated fat and trans fat
Low complex carbohydrate intake
High intake of salty or pickled foods
Low vitamin and mineral intake
Excessive alcohol intake Source: Sizer and Whitney Chpt. 11.
So how does diet affect the probability of these chronic diseases? That is, what are the
mechanisms through which the diet works to increase the probability of these diseases?
A complete answer to this question is beyond the scope of this review but it is important
to understand the processes at some rather basic level. Here we will just cover the
relationship between diet and the cardiovascular diseases and diet and cancer. The
connection between diet and cardiovascular disease is much better understood than the
relationship between diet and cancers.
Diet and Cardiovascular Disease About 80 million people in the US suffer from some form of cardiovascular disease
(CVD). The common form of CVD is atherosclerosis. Atherosclerosis is the condition
of plaques forming on the artery walls. The common name of atherosclerosis is
“hardening of the arteries.” Everyone will have various degrees of atherosclerosis, the
issues is how to reduce it. Figure 3 gives an overview of the sequence of progression of
atherosclerosis.
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Figure 3. Progression of Atherosclerosis (Source??WEB)
Atherosclerosis usually begins with the accumulation of soft, fatty streaks along the inner
walls of the arteries, especially at branch points. These gradually enlarge and become
hardened fibrous plaques that damage artery walls. Plaques are mounds of lipid material
mixed with smooth muscle cells and calcium that develop in the artery walls. A diet high
in saturated fat is a major contributor to the development of plaques and the progression
of atherosclerosis. However, atherosclerosis is a much more complex process than just
an accumulation of lipid material on the cell walls. Atherosclerosis is a complex
response of the artery to tissue damage and inflammation.
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Inflammation is part of the body’s immune defense against injury, infection, or
allergens and is marked by increased blood flow, release of chemical toxins, and the
attraction of white blood cells to the infected area. The damage may begin from a
number of factors interacting with cells that line the arteries but the two most important
are High LDL cholesterol and Hypertension.
High LDL Cholesterol and Artery Integrity Cholesterol is a member of the group of lipids known as sterols and is a soft, waxy
substance made in the body for a variety of purposes. LDL is the acronym for low-
density lipoproteins. Lipoproteins are clusters of lipids associated with proteins, which
serve as the transport vehicle for lipids in the blood and lymph system. Consequently,
low-density lipoproteins (LDL) denotes one of the major classes of lipoproteins and
they carry cholesterol to the cells, including those lining the arteries. They are the
lipoproteins most likely to produce plaques in arteries (i.e., they are atherogenic). On the
other hand, high-density lipoproteins (HDL) denotes the other main class of
lipoproteins but they carry cholesterol away from the cells to the liver for recycling to
other uses or for disposal. LDL cholesterol and HDL cholesterol are strongly linked to a
person’s risk of developing atherosclerosis and heart disease. The higher the LDL, the
higher the risk of atherosclerosis and heart disease. The lower the HDL, the higher the
risk atherosclerosis and heart disease.
The basic process is that when cells lining arteries are damaged inflammation is
triggered which signals to the immune system to send white blood cells to the site to try
to repair the damage. Soon, particles of LDL cholesterol become trapped in the blood
vessel walls and become oxidized. The white blood cells – macrophages – flood the
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scene to scavenge and remove the oxidized LDL, but to no avail. As the macrophages
become engorged with oxidized LDL, they become foam cells, which themselves become
triggers of oxidation and inflammation that attract more immune scavengers to the scene.
Muscle cells of the arterial wall proliferate in an attempt to heal the damage, but they mix
with foam cells to form hardened areas of plaque. This cycle repeats until the inner
artery walls become virtually covered with disfiguring plaques. The buildup of plaques
in turn affects blood pressure and blood clot formation.
Normally, arteries expand with each heartbeat to accommodate the pulses of blood
that flow through them. Arteries hardened and narrowed by plaques cannot expand, so
blood pressure rises. High blood pressure is also known as hypertension. The increased
blood pressure damages the artery walls further and strains the heart. As pressure builds
up in the artery, the arterial wall may become weakened and balloon out. This ballooning
out is called an aneurism. If an aneurysm burst, especially one in the aorta, the
individual will bleed to death. In addition, abnormal blood clotting also threatens life.
Atherosclerosis, arterial damage, plaques in the arteries, and inflammation all favor the
formation of blood clots. In atherosclerosis, a sudden spasm of the artery wall or surging
in blood pressure can tear away part of the fibrous coat covering a plaque, causing it to
rupture. When a plaque ruptures, the body responds to the damage as an injury – by
clotting the blood. A stationary blood clot is called a thrombus. A thrombus that has
grown enough to close off a blood vessel is called a thrombosis. A thrombosis closing
off vessels that feed the heart muscle is called a coronary. A thrombosis closing off
vessels that feed the brain is called a cerebral thrombosis. Sometimes a thrombus
breaks loose and travels through the blood vessels. This is called an embolus and
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embolus that causes sudden closure of a blood vessel is called an embolism. Heart
attacks and strokes can be caused by either a thrombosis or an embolism.
A diet high in saturated fat and trans fatty acids contributes to high blood LDL
cholesterol. Conversely, reducing those fats in the diet lowers blood LDL cholesterol and
may reduce the risk of CVD. So the logic chain between diet and CVD is
↓ Saturated fat and trans fat ⇒ ↓ LDL cholesterol ⇒ ↓ CVD.
Diet and Cancer
Cancer is a disease where cells multiply abnormally and excessively disrupting normal
functioning of one or more organs. The actual mechanism relating diet to cancer is not as
well understood as in the case of CVD. Cancer ranks second only to heart disease as the
leading cause of death and disability in the United States. For some groups, such as
women age 40 to 79 and men 60 to 79 years, cancer is the leading cause of death. One of
the most challenging aspects of making the connection between diet and cancer is that
there are many different types of cancer and cancer can be located in a wide variety of
locations in the body. An estimated 20 to 50 percent of cancers are influenced by diet
and these relationships are the focus of this section.
Foods play three roles in cancer:
1. Certain foods and their components may cause cancer.
2. Certain foods and their components may promote cancer.
3. Certain foods and their components may protect against cancer.
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As we see here the term may indicates that there are several other risk factors that can
affect the cause, promotion, and protection against cancer. So again, as discussed, when
we talk about the effects of diet we are really making a ceteris paribus statement.
Table 15 list some of the majors types of cancers, the main risk factors, and possible
protective dietary factors.
Table 15. Examples of Cancers and Diet Connections Type of Cancer Intake Association Possible Protective Effect Breast High calories; low
vitamin A; probably high saturated fat and meat; possibly high sucrose
Monosaturated fats; vegetables and fruits; calcium and vitamin D
Cervical Folate Deficiency Adequate folate intake; possibly, fruits and vegetables
Kidney Possibly, high red meat Fruits and vegetable, especially orange-colored and dark green
Liver High iron Vegetables, especially yellow and green
Lung Low vitamin A Fruits and Vegetables Ovarian Possibly, high lactose Vegetables, especially green
leafy Pancreatic Possibly, high red meat Possibly, fruits and vegetables,
especially yellow and green Prostate High in fats, especially
saturated fats and possibly milk products
Possibly cooked tomatoes, soybeans, soy products, flaxseed
Stomach High salt, refined flour starch
Fresh fruits and vegetables, especially tomatoes; possibly foods high in vitamin A and beta-carotene
Source: Sizer and Whitney Chpt. 11.
There are two general points that emerge from table 15. First, there is a heavy dose of
uncertainty and qualification with the term “possibly” repeated several places. Second,
the common theme is that an increased consumption of fruits and vegetables may have a
protective effect.
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E. A Foreshadowing Conclusion
In this module we have taken a whirlwind review of basic nutrition. The focus has been
on the technical relationships between food and nutrients and the dietary
recommendations in terms of nutrients, foods, and health. This emphasis has been
purposeful with a look ahead toward the economics section. A key requirement for
making an optimal economic decision is the presence of accurate, clear, and full
information – what an economist would call complete information. Economic decision
can be difficult enough when there is complete information but they become much more
difficult when there is incomplete information (i.e., when the information is either
inaccurate, unclear, or not easily available or processed). As this brief review has
hopefully made clear, the study of nutrition, food, and health is “informationally dense”
in that there is a lot of information that must be processed in order to understand even the
basics of the connection between nutrition, foods, and health. This is perhaps not
surprising as it is a discipline in its own right but as will become evident in the next
module, nutrition information is just one type of information the consumer must take into
account when making food, nutrient, and ultimately health choices.