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13
Applications of Dietary
Reference Intakes for
Macronutrients
This chapter presents a general discussion of the appropriate uses of
the Dietary Reference Intakes (DRIs) in the assessment and planning of
diets for individuals and for groups. It also provides guidance for the use
of the DRIs developed for the nutrients presented in this report, including
specific examples and special considerations.
OVERVIEW
The Dietary Reference Intakes (DRIs) may be used for many purposes,
most of which fall into two broad categories: assessing current nutrient intakes
and planning for future nutrient intakes. Each category may be further
subdivided into uses for individual diets and for group diets (Figure 13-1).
For example, the Recommended Dietary Allowance (RDA), Estimated
Average Requirement (EAR), and Tolerable Upper Intake Level (UL) may
be used in assessing the diet of an individual as one aspect of a nutritional
status assessment. The RDA and Adequate Intake (AI) may be used as a
basis for planning a diet for the same individual. Likewise, the EAR and
UL are used to assess the nutrient intakes of a group, such as persons
participating in dietary surveys conducted as part of the National Nutrition
Monitoring System. The EAR and UL can also be used to plan nutritionally
adequate diets for groups, such as people receiving meals in nursing homes,
schools, prisons, and other group settings.
In the past, RDAs in the United States and Recommended Nutrient
Intakes (RNIs) in Canada were the primary reference standards available
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A PPLICATIONS OF DRIs FOR MACRONUTRIENTS
FIGURE 13-1 Conceptual framework—uses of Dietary Reference Intakes.
a Food plus supplements.
to health professionals for assessing and planning diets of individuals and
groups and for making judgments about inadequate and excessive intake.
However, neither the former RDAs nor the RNIs were ideally suited for
many of these purposes (IOM, 1994). The DRIs provide a more complete
set of reference values. The transition from using the former RDAs and
RNIs to using all of the DRIs appropriately will require time and effort by
health professionals and others.
Appropriate uses of each of the new DRIs are described briefly in this
chapter and in more detail in a report on the application of the DRIs in
assessment (IOM, 2000) and in a forthcoming report on their uses in
planning. Included in this chapter are specific applications to the nutrients
discussed in this report. Details on how the DRIs are set with reference to
specific life stage and gender groups, and the primary criterion that defines
adequacy for each of these nutrients are given in Chapters 5 through 10.
ASSESSING NUTRIENT INTAKES OF INDIVIDUALS
Dietary assessment methods have several inherent inaccuracies. One is
that individuals underreport their intakes (Mertz et al., 1991; Schoeller,
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938 DIETARY REFERENCE INTAKES
1995; Schoeller et al., 1990), and it appears that obese individuals often do
so to a greater extent than do normal-weight individuals (Heitmann and
Lissner, 1995). There is no method to adjust intakes to account for under-
reporting by individuals and much work is needed to develop an acceptable
method. Another inherent inaccuracy is the quality of food composition
databases.
Furthermore, large day-to-day variations in intake, which are exhibited
by almost all individuals, mean that it often takes a prohibitively large
number of days of intake measurement to approximate usual intake
(Basiotis et al., 1987). As a result, caution is indicated when interpreting
nutrient assessments based on self-reported dietary data covering only a
few days of intake. Data on nutrient intakes should be interpreted in com-
bination with information on typical food usage patterns to determine if
the recorded intakes are representative of that individual’s usual intake.
Finally, because there is considerable variation in intakes both within
and between individuals, as well as variation associated with the require-
ment estimate, other factors must be evaluated in conjunction with the
diet. The Dietary Reference Intakes (DRIs) should be used in conjunction
with other data in assessing the adequacy of the diet of a specific indi-
vidual. The nutritional status of an individual can be definitively deter-
mined only by a combination of dietary, anthropometric, physiological
and biochemical data.
Using the Estimated Average Requirement and the
Recommended Dietary Allowance
The Estimated Average Requirement (EAR) estimates the median of a
distribution of requirements for a specific life stage and gender group, but
it is not possible to know where an individual’s requirement falls within
this distribution without further anthropometric, physiological, or bio-
chemical measures. Thus from dietary data alone, it is only possible to
estimate the likelihood of nutrient adequacy or inadequacy. Furthermore,
only rarely are precise and representative data on the usual intake of an
individual available, adding additional uncertainty to the evaluation of an
individual’s dietary adequacy.
An approach for using data from dietary records or recalls to estimate
the likelihood that an individual’s nutrient intake is adequate is presented
in Dietary Reference Intakes: Applications in Dietary Assessment (IOM, 2000).
This approach is appropriate for nutrients with symmetrical requirement
distributions, which is thought to be true for all macronutrients in this
report for which EARs have been established. The following data are
required:
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A PPLICATIONS OF DRIs FOR MACRONUTRIENTS
• individual’s mean nutrient intake over a given number of days
• day-to-day standard deviation (SD) of intakes for each nutrient of
interest, as estimated from larger data sets for the appropriate life stage
and gender group
• EAR
• SD of the nutrient requirement in the individual’s life stage and
gender group.
From this information a ratio is computed that compares the magnitude
of difference between the individual’s intake and the EAR to an estimate
of variability of intake and requirements. The bigger the difference between
intake and EAR and the lower the variability of intakes and requirements,
the greater is the degree of certainty in assessing whether the individual’s
nutrient intake is adequate, inadequate, or excessive. This approach is
quantitative and should be used only when the data listed above are available.
However, in the more common situation where the estimate of usual
intake is not based on actual 24-hour recalls or records, but on dietary
history or food frequency questionnaires, a qualitative interpretation of
intakes can be used. For example, many practitioners use the diet history
method to construct a likely usual day’s intake, but the error structure
associated with this method is unknown. While the error associated with
food frequency questionnaires has been evaluated (Carroll et al., 1996;
Liu, 1994), use of these tools for quantitative nutrient assessment is still
not possible due to lack of accurate portion size estimates and grouping of
food items (IOM, 2000). Thus, a practitioner should be cautious when
using this method to approximate usual intakes.
Users of the DRIs may find it useful to consider that observed intakes
below the EAR probably need to be improved (because the probability of
adequacy is 50 percent or less) and those between the EAR and the Recom-
mended Dietary Allowance (RDA) probably need to be improved (because
the probability of adequacy is less than 97 to 98 percent). Only if intakes
have been observed for a large number of days and are at the RDA, or
observed intakes for fewer days are well above the RDA, should one have a
high level of confidence that the intake is adequate. Such considerations
are not applicable in the case of energy intake, which should match energy
expenditure in individuals maintaining desirable body weight (see later
section, “Planning Nutrient Intakes of Individuals,” and Chapter 5).
Using the Adequate Intake
Adequate Intakes (AIs) have been set for infants younger than 7 months
of age for n-3 and n-6 polyunsaturated fatty acids and protein. By defini-
tion, infants born at term who are exclusively fed human milk by healthy
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940 DIETARY REFERENCE INTAKES
mothers consume an adequate nutrient intake. Infants who consume
formulas with a nutrient profile similar to human milk (after adjustment
for differences in bioavailability) are also assumed to consume adequate
levels of nutrients. When an infant formula contains nutrient levels that
are lower than those found in human milk, the likelihood of nutrient
adequacy for infants who consume this formula cannot be determined
because data on infants fed lower concentrations of nutrients are not avail-
able. AIs have also been established for infants 7 to 12 months of age for
all nutrients covered in this report except protein, and for all individuals
for Total Fiber and the n-3 and n-6 polyunsaturated fatty acids.
Equations that can be used to estimate the degree of confidence that
an individual’s usual intake meets or exceeds the AI are presented (IOM,
2000). The data required include the individual’s reported intake over a
given number of days, the AI for the age/gender group, and the day-to-
day (within-person) SD for the nutrient of interest, as estimated from
larger data sets for the appropriate life stage and gender group. Usual
individual intakes that are equal to or above the AI can be assumed to be
adequate. However, the likelihood of inadequacy of usual intakes below
the AI cannot be determined.
Using the Tolerable Upper Intake Level
The Tolerable Upper Intake Level (UL) is used to examine the possi-
bility of over-consumption of a nutrient. Equations have been developed
to determine the degree of confidence that an individual’s intake is below
the UL (IOM, 2000). If an individual’s usual nutrient intake remains below
the UL, there is no risk of adverse effects from excessive intake. At intakes
above the UL, the potential for risk of adverse effects increases. However,
the intake at which a given individual will develop adverse effects as a
result of taking large amounts of one or more nutrients is not known with
certainty. No ULs were set for the macronutrients in this report. However,
there is no established benefit to almost all healthy individuals who con-
sume amounts of nutrients that exceed the RDA or AI.
Equations that can be used to estimate the degree of confidence that
an individual’s usual intake equals or exceeds the UL are presented in
Dietary Reference Intakes: Applications in Dietary Assessment (IOM, 2000). The
data required include the individual’s reported intake over a given number
of days, the UL for the life stage and gender group, and the day-to-day
(within-person) SD for the nutrient of interest, as estimated from larger
data sets for the appropriate life stage and gender group.
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A PPLICATIONS OF DRIs FOR MACRONUTRIENTS
Using the Acceptable Macronutrient Distribution Range
In addition to presenting DRIs for macronutrients, this report also
presents Acceptable Macronutrient Distribution Ranges (AMDRs) for indi-
viduals as a proportion of total energy intake. The AMDRs represent
intakes that minimize the potential for chronic disease over the long-term,
permit essential nutrients to be consumed at adequate levels, and should
be associated with adequate energy intake and physical activity to maintain
energy balance. The AMDRs for adults are 20 to 35 percent of energy from
fat (including 0.6 to 1.2 percent of energy from n-3 polyunsaturated fatty
acids and 5 to 10 percent of energy from n-6 polyunsaturated fatty acids),
45 to 65 percent of energy from carbohydrate, and 10 to 35 percent of
energy from protein. For children, the AMDRs for total fat are 30 to 40 per-
cent between the ages of 1 and 3 years, and 25 to 35 percent between the
ages of 4 and 18 years. AMDRs for protein and carbohydrate do not vary
with age.
To estimate the degree of confidence that an individual’s diet falls
within the AMDR, the equations developed could be used to estimate the
degree of confidence that the individual’s intake exceeds the AI or remains
below the UL (IOM, 2000). The equation for the AI could be used to
determine the degree of confidence that intake is above the lower end of
the AMDR, and the equation for the UL could be used to determine the
degree of confidence that intake is below the upper end of the AMDR.
The data required include the individual’s average intake of the macro-
nutrient of interest as a percent of energy intake over a given number of
days, the boundaries of the AMDR, and the day-to-day (within-person) SD
of percent energy intake, as estimated from larger data sets for the appro-
priate life stage and gender group.
ASSESSING NUTRIENT INTAKES OF GROUPS
The assessment of nutrient adequacy for groups of people requires
unbiased, quantitative information on the intake of the nutrient of interest
by individuals in the group. Care must be taken to ensure the quality of
the information upon which assessments are made so that they are not
underestimates or overestimates of total nutrient intake. Estimates of total
nutrient intake, including amounts from supplements, should be obtained.
It is also important to use appropriate food composition tables with accu-
rate nutrient values for the foods as consumed.
Several steps must be taken to assess the intake of a group. First, the
intake distribution must be adjusted to remove the effect of day-to-day
variation of individual intake. This can be accomplished either by collect-
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942 DIETARY REFERENCE INTAKES
FIGURE 13-2 Comparison of 1-day and usual intakes for estimating the propor-
tion of a group consuming below the Estimated Average Requirement (EAR).
ing dietary data for each individual over a large number of days or by
statistical adjustments to the intake distribution. The statistical adjustments
are based on assumptions about the day-to-day variation derived from
repeat measurements of a representative subset of the group under study
(Nusser et al., 1996). When this adjustment is performed and observed
intakes are thus more representative of the usual diet, the intake distribu-
tion narrows, giving a more precise estimate of the proportion of the group
with usual intakes below requirements (Figure 13-2). An explanation of
this adjustment procedure has been presented in two previous reports
(IOM, 2000; NRC, 1986).
A statistical approach is then used to combine the information on
nutrient intakes with the information on nutrient requirements in order
to determine the apparent percent prevalence of nutrient inadequacy in
the group. Two approaches are briefly described below and in detail else-
where (IOM, 2000; NRC, 1986).
The Probability Approach
Using the probability approach requires knowledge of both the distri-
bution of requirements and the distribution of usual intakes for the popu-
lation of interest. As described previously (IOM, 2000; NRC, 1986), the
probability approach involves: (1) determining the risk of inadequacy for
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A PPLICATIONS OF DRIs FOR MACRONUTRIENTS
each individual in the population and then (2) averaging the individual
probabilities of inadequacy across the group. Appendix C of Dietary Refer-
ence Intakes: Applications in Dietary Assessment (IOM, 2000) demonstrates
how to carry out the necessary calculations to obtain a prevalence estimate
for a group. Statistical programs (e.g., SAS or similar software) can be used
to carry out these procedures.
The EAR Cut-Point Method
In most situations a cut-point method using the Estimated Average
Requirement (EAR) may be used to estimate the prevalence of inadequate
intakes. This cut-point method is a simplification of the full probability
approach of calculating the prevalence of inadequacy described by the
National Research Council (NRC, 1986). The cut-point method allows the
prevalence of inadequate intakes in a population to be approximated by
determining the percentage of individuals in the group whose usual intakes
are less than the EAR for the nutrient of interest. This method assumes
that the intake and requirement distributions are independent, an assump-
tion that is not valid for the energy requirements addressed in this report
because energy intakes are highly correlated to energy expenditure. The
cut-point method further assumes that the variability of intakes among
individuals within the group under study is at least as large as the variability
of their requirements. This assumption is usually warranted in free-living
populations. Finally, it assumes that the requirement distribution is sym-
metrical. This is thought to be true for all of the macronutrients discussed
in this report.
Using the Estimated Average Requirement
If the assumptions for the EAR cut-point method are met, the preva-
lence of inadequate intakes may be estimated by the proportion of the
distribution of usual intakes that falls below the EAR. An example of using
the EAR cut-point method to assess the dietary carbohydrate adequacy of
women aged 31 to 50 years follows. Dietary intake data are available from
the 1994–1996 Continuing Survey of Food Intakes by Individuals. Esti-
mated intakes are based on respondents’ intakes, which were adjusted to
remove within-person variability using the Iowa State University method
(Appendix Table E-2). The EAR for women in this age group is 100 g/day.
Examination of the distribution of usual carbohydrate intake reveals that
intakes at the 1st and 5th percentiles are 87 and 118 g/day, respectively.
Thus, fewer than 5 percent of women in this age group appear to have
inadequate carbohydrate intakes.
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944 DIETARY REFERENCE INTAKES
Overestimates of the prevalence of inadequate intakes could result if
the data used are based on intakes that are systematically underreported
or if foods rich in the nutrient of interest are underreported. Such under-
reporting is common in national surveys (Briefel et al., 1997). Currently, a
method for adjusting intakes to compensate for underreporting by indi-
viduals is not available, and much work is needed to develop an acceptable
method. Conversely, underestimates of the prevalence of inadequacy could
result if foods rich in the nutrient of interest were overreported. A more
extensive discussion of potential sources of error in self-reported dietary
data can be found in the report Dietary Reference Intakes: Applications in
Dietary Assessment (IOM, 2000).
Comparison of Assessments Using the Probability Approach and
Biochemical Assessment
If requirement estimates are correct, dietary intake data are reliable
estimates of true usual intake, and biochemical measures reflect the same
functional criterion used to set the requirement of a nutrient for the same
population, then the prevalence of apparently inadequate dietary intakes
and biochemical deficiencies or indicators of inadequacy should be similar.
Using the Recommended Dietary Allowance
The Recommended Dietary Allowances are not useful in estimating
the prevalence of inadequate intakes for groups. As described above, the
EAR should be used for this purpose.
Using the Adequate Intake
In this report Adequate Intakes (AIs) are assigned for all nutrients for
infants through the age of 6 months and reflect the average intake of
infants receiving human milk. Human milk and formulas with the same
nutrient composition as human milk (after adjustment for bioavailability)
provide the appropriate levels of nutrients for full-term infants of healthy,
well-nourished mothers. For infants ages 7 to 12 months, AIs are set for
carbohydrate and n-3 and n-6 polyunsaturated fatty acids and reflect the
average intakes of infants receiving human milk and complementary foods.
Groups of infants consuming formulas with lower levels of nutrients than
that found in human milk may be at some risk of inadequacy, although
the prevalence of inadequacy cannot be quantified.
This report provides AIs for all life stage and gender groups for Total
Fiber and n-3 and n-6 polyunsaturated fatty acids. Groups with median
intakes equal to or above the AI for Total Fiber and n-3 and n-6 poly-
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A PPLICATIONS OF DRIs FOR MACRONUTRIENTS
unsaturated fatty acids can be assumed to have a low prevalence of inade-
quacy (provided that intake variability does not exceed that of the healthy
group used to establish the AI). However, when the AI is not set as a mean
intake of a healthy group (e.g., fiber), confidence in this assessment should
be less than it would be if the AI represents the median intake of a healthy
group. It is important to note that group median intakes below the AI
cannot be assumed to be inadequate.
Using the Tolerable Upper Intake Level
The proportion of the population with usual intakes below the Toler-
able Upper Intake Level (UL) is likely to be at no risk of adverse effects
due to overconsumption. However, the proportion of the population con-
suming above the UL may potentially be at some risk.
The mean intake of a population cannot be used to evaluate the preva-
lence of intakes above the UL. A distribution of usual intakes, including
intakes from supplements, is required to assess the proportion of the popu-
lation that might be at risk of over-consumption. However, if the mean or
median intake is equal to or greater than the UL, it suggests that the
number of individuals with excessive intake is high and warrants further
investigation.
Using the Acceptable Macronutrient Distribution Range
Although primarily directed at individuals, the Acceptable Macronutrient
Distribution Range (AMDR) also permits assessment of populations. By
determining the proportion of the group that falls below, within, and
above the AMDR, it is possible to assess population adherence to recom-
mendations and to determine the proportion of the population that is
outside the range. If significant proportions of the population fall outside
the range, concern could be heightened for possible adverse consequences.
Planning and public health messages can then be instituted to attempt to
attain a low prevalence of intakes below or above the AMDR.
For example, the AMDR for total fat intake of children 4 to 18 years of
age is 25 to 35 percent of energy. Appendix Table E-6 presents data on the
usual daily intake of total fat as a percentage of energy intake and indi-
cates that for all groups of children and adolescents, the 5th percentile of
intake is at least 25 percent. Thus, fewer than 5 percent of children have
intakes below the AMDR for total fat. The 75th percentiles of intake are
close to 35 percent, suggesting that approximately 25 percent of children
and adolescents have intakes above the AMDR for total fat. Intakes of the
remaining 70 to 75 percent fall within the AMDR.
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946 DIETARY REFERENCE INTAKES
PLANNING NUTRIENT INTAKES OF INDIVIDUALS
Using the Recommended Dietary Allowance
Individuals should use the Recommended Dietary Allowance (RDA)
as the target for their intakes for those nutrients for which RDAs have
been established. Intakes at this level ensure that the risk to individuals of
not meeting their requirements is very low (2 to 3 percent). For example,
the RDA for protein for adults is 0.8 g/kg/day, or 56 and 46 g/day for
reference men and women weighing 70 kg and 57 kg, respectively. For a
small adult weighing 45 kg, the recommended protein intake would be
36 g/day, while for a larger adult weighing 90 kg, the RDA would be
72 g/day.
Using the Adequate Intake
Adequate Intakes (AIs) are set for infants younger than 7 months of
age for all nutrients, and for all nutrients except protein and indispens-
able amino acids for infants 7 through 12 months of age. Human milk, by
definition, supplies the AI for a nutrient for term infants; it is not neces-
sary to plan additional sources of intake for infants exclusively fed human
milk. Likewise, an infant formula with a nutrient profile similar to human
milk (after adjustment for differences in bioavailability) should supply
adequate nutrients for an infant.
In this report AIs are also set for children, adolescents, and adults for
Total Fiber and n-3 and n-6 polyunsaturated fatty acids. Accordingly, indi-
viduals should use the AI as their goal for intake of these nutrients.
Using the Tolerable Upper Intake Level
Tolerable Upper Intake Levels (Uls) were not set for the macronutrients
covered in this report.
Using the Acceptable Macronutrient Distribution Range
In addition to meeting the RDA or AI and remaining below the UL,
an individual’s intake of macronutrients should be planned so that carbo-
hydrate, total fat, n-3 and n-6 polyunsaturated fatty acids, and protein are
within their respective Acceptable Macronutrient Distribution Ranges.
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requirement for carbohydrate without difficulty by consuming a varied
diet containing breads, rice, other grain products, potatoes, fruits, vege-
tables, milk products, and (in moderate amounts) starch- or sugar-based
snack foods.
As discussed in Chapter 11, to achieve a healthful balance of the macro-
nutrients that supply energy, the AMDR for total carbohydrate is 45 to
65 percent of energy. This range allows for intakes of carbohydrate that
exceeds the RDA of 130 g/day. The carbohydrate content of most U.S.
diets is either less than or within this range (see Appendix Table E-3), but
it is more likely to be within this range if food selections emphasize grains,
fruits, and vegetables prepared with minimal or modest amounts of fat.
Added Sugars
Added sugars are defined as sugars and syrups that are added to foods
during processing or preparation. Major sources of added sugars include
soft drinks, cakes, cookies, pies, fruitades, fruit punch, dairy desserts, and
candy (USDA/HHS, 2000). Specifically, added sugars include white sugar,
brown sugar, raw sugar, corn syrup, corn-syrup solids, high-fructose corn
syrup, malt syrup, maple syrup, pancake syrup, fructose sweetener, anhydrous
dextrose, and crystal dextrose. Since added sugars provide only energy
when eaten alone and lower nutrient density when added to foods, it is
suggested that added sugars in the diet should not exceed 25 percent of
total energy intake. Usual intakes above this level place an individual at
potential risk of not meeting micronutrient requirements. Nutrient data
on added sugars has only recently become available in the U.S. Depart-
ment of Agriculture’s (USDA) Pyramid Servings Database, which includes
data on added sugars for over 7,000 foods. Appendix Table D-1 describes
the Third National Health and Nutrition Examination Survey (NHANES
III) results on the distribution of intakes of added sugar.
To assess the sugar intakes of groups requires knowledge of the distri-
bution of usual added sugar intake as a percent of energy intake. Once this
is determined, the percentage of the population exceeding the maximum
suggested level can be evaluated. Because the criterion for the suggested
maximum intake level of added sugars is the risk of associated inadequate
intakes of micronutrients, such an evaluation would be complemented by
assessing micronutrient intakes, as described in the DRI report for those
nutrients (IOM, 2001) and the report on dietary assessment (IOM, 2000).
Dietary, Functional, and Total Fiber
Dietary Fiber is defined in this report as nondigestible carbohydrates
and lignin that are intrinsic and intact in plants. Functional Fiber is defined
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958 DIETARY REFERENCE INTAKES
as isolated, nondigestible carbohydrates that have beneficial physiological
effects in humans. Total Fiber is the sum of Dietary Fiber and Functional Fiber.
Fiber includes viscous forms that lower serum cholesterol concentrations
(i.e., soluble fiber: oat bran, beans) and the bulking agents that improve
laxation (i.e., insoluble fiber: wheat bran). The AI for Total Fiber is 38 and
25 g/day for 19- to 50-year-old men and women, respectively, based on a
reduced risk of coronary heart disease for those within the highest quintiles
of dietary fiber consumption (g/1,000 kcal) in several epidemiological
studies and the median energy intake (Appendix Table E-1). Unlike the
AI for some nutrients, this AI does not describe the median Total Fiber
intake of a healthy population. Instead, it is based on health benefits asso-
ciated with consuming foods that are rich in fiber. Based on CSFII data
(Appendix Table E-4), the median Dietary Fiber intakes are 16.5 to 17.9 g/day
for men and 12.1 to 13.3 g/day for women. Thus, it is evident that to meet
the AI, most people will need to substantially increase their Total Fiber intake.
Usual intakes that meet or exceed the AI can be assumed adequate, but the
likelihood of inadequacy of usual intakes below the AI cannot be determined.
Fiber consumption can be increased by substituting whole grain or
products with added cereal bran for more refined bakery, cereal, pasta,
and rice products; by choosing whole fruits instead of fruit juices; by con-
suming fruits and vegetables without removing edible membranes or peels;
and by eating more legumes, nuts, and seeds. For example, whole wheat
bread contains three times as much Dietary Fiber as white bread, and the
fiber content of a potato doubles if the peel is consumed. The soluble and
insoluble fiber components of 228 U.S. foods have been published by
Marlett and Cheung (1997).
Dietary fiber data are listed for a wide range of foods in the USDA
Nutrient Database for Standard Reference (USDA, 2001). The dietary fiber
values in the USDA database represent Total Fiber (including both dietary
and functional fiber) as defined in this report. For most diets (those that
have not been fortified with Functional Fiber that was isolated and added for
health purposes), the contribution of Functional Fiber is minor relative to
the naturally occurring Dietary Fiber. For example, the Functional Fiber con-
tent for foods such as fat-free yogurts and ice creams that contain added
guar gums and carrageenan is so low that the USDA database generally
indicates zero dietary fiber for these foods. Although the AI is set for Total
Fiber, this AI is generally based upon the fibers present in foods, and until
these terms are further incorporated into nutrient databases, it is appro-
priate to apply the Dietary Fiber data from the USDA database to the AI for
Total Fiber.
Because there is insufficient evidence of deleterious effects of high
Dietary Fiber as part of an overall healthy diet, a Tolerable Upper Intake
Level has not been established.
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Total Fat and n-3 and n-6 Polyunsaturated Fatty Acids
Total Fat
No RDAs or AIs are set for total fat, but an AMDR of 20 to 35 percent
of energy is recommended for adults (Chapter 11). Thus, when planning
diets for individuals, it is necessary to first calculate the individual’s esti-
mated energy expenditure, determine 20 and 35 percent of this number
in kilocalories, and then divide by 9 kcal/g to get the range of fat intake in
grams per day. For example, a person whose energy expenditure was
2,300 kcal/day should aim for an energy intake from fat of 460 to 805 kcal/
day. In grams of total fat, intake should be between 51 and 89 g/day.
Likewise, when assessing fat intakes of individuals, the goal is to deter-
mine if usual energy intake from total fat is between 20 and 35 percent. As
illustrated above, this is a relatively simple calculation assuming both usual
fat intake and usual energy intake are known. However, because dietary
data are typically based on a small number of days of records or recalls, it
may not be possible to state with confidence that a diet is within this range.
As explained in the DRI dietary assessment report (IOM, 2000), an adjust-
ment can be made for the likelihood that these are not representative
days, based on the day-to-day variation in fat intake and the number of
days of dietary data.
When planning fat intakes for groups, the goal is to minimize the
intakes of total fat that are outside the AMDR of 20 to 35 percent of energy
from fat. If planning is for a confined population, a procedure similar to
the one described for individuals may be used: determine the necessary
energy intake from the planned meals and plan for a fat intake that pro-
vides between 20 and 35 percent of this value. If the group is not confined,
then planning intakes is more complex and ideally begins with knowledge
of the distribution of usual energy intake from fat. Then the distribution
can be examined, and feeding and education programs designed to either
increase, or more likely, decrease the percent of energy from fat.
Assessing the fat intake of a group requires knowledge of the distribution
of usual fat intake as a percent of energy intake. Once the distribution is
described, the percent of the population outside the AMDR can be calcu-
lated. For example, Appendix Table E-6 shows that in the CSFII, less than
1 percent of the population was below 20 percent of energy from fat, while
over 50 percent consumed greater than 35 percent of energy from fat.
n-3 and n-6 Polyunsaturated Fatty Acids
n-3 and n-6 Polyunsaturated fatty acids have an AI based on median
intakes of linoleic acid and α-linolenic acid from CFSII, respectively. In
addition to an AI, an AMDR is provided for n-3 and n-6 fatty acids. The
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960 DIETARY REFERENCE INTAKES
suggested range is 0.6 to 1.2 percent of energy from n-3 fatty acids and 5 to
10 percent of energy from n-6 fatty acids. Thus, there are several consider-
ations when planning and evaluating n-3 and n-6 fatty acid intakes. Usual
intakes that meet or exceed the AI can be assumed adequate, but the
likelihood of inadequacy of usual intakes below the AI cannot be deter-
mined. Assessing n-3 and n-6 fatty acid intakes of groups against the AMDR
requires knowledge of the distribution of usual fatty acid intake as a per-
centage of energy intake. Once the distribution is described, the percent-
age of the population outside the AMDR can be calculated.
Saturated Fatty Acids, Trans Fatty Acids, and Cholesterol
No RDAs, AIs, or AMDRs are provided for saturated fatty acids, trans
fatty acids, and cholesterol. However, with increasing intakes of either of
these three nutrients, there is an increased risk of coronary heart disease.
Chapter 11 provides some dietary guidance on ways to reduce the intake
of saturated fatty acids, trans fatty acids, and cholesterol. For example,
when planning diets, it is desirable to replace saturated fat with either
monounsaturated or polyunsaturated fats to the greatest extent possible.
Protein and Amino Acids
The EARs and RDAs for protein and amino acids have been expressed
as grams per kilogram per day, the first DRIs to be expressed in this way.
This implies that requirements and recommended intakes vary among indi-
viduals of different sizes, and should be individualized when used for
dietary assessment or planning. The potential implications of this are
discussed below.
Dietary Assessment
For most nutrients for which EARs have been defined, the prevalence
of inadequate intakes can be estimated as the proportion of the distribu-
tion of usual intakes that falls below the EAR using the EAR cut-point
method (IOM, 2000). However, this method requires a number of assump-
tions, including that the individual requirement for the nutrient in
question has a symmetric distribution. As described in Chapter 10, the
distribution of the individual requirement for protein for adults is skewed,
however, this skewing appears to be slight and the EAR cut-point method
is expected to provide a good approximation to prevalence.
However, if more accuracy is needed, the “probability approach” can
be used. This approach has been described elsewhere (IOM, 2000; NRC,
1986), and its application for assessing the prevalence of inadequacy of
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iron intakes has been illustrated (IOM, 2002). The probability approach
for assessing the adequacy of protein intakes is identical to that outlined
for iron, with the simplification that percentiles of protein requirement
can be explicitly calculated from the formula given in Chapter 10 (“RDA
Summary, Ages 19–50 Years”).
Planning the Diet
When planning a diet for an individual, recommended intakes can be
determined on the basis of the individual’s body weight. Although the RDA
for the reference adult male is 56 g/day of protein (based on 0.8 g/kg/day
for a 70-kg person), the recommended intakes for men weighing 60 kg
and 90 kg would be 48 and 72 g/day, respectively.
It should be noted that the DRIs are intended to apply to healthy
individuals. Thus, determining a recommended protein intake based on
current body weight may not be appropriate for those who are signifi-
cantly underweight or overweight. For example, a medical professional
might choose to specify a protein intake for a malnourished, underweight
patient based on what the patient’s body weight would be if he were
healthy. A patient weighing 40 kg, whose body weight when healthy was
55 kg, could thus have a recommended protein intake of 44 g/day (55 kg
× 0.8 g/kg), rather than the 32 g/day that would be determined based on
current weight. Conversely, protein intakes recommended for individuals
who are morbidly obese could be based on the amounts recommended for
those with more normal body weights.
Are Planning and Assessing Intakes of Indispensable
Amino Acids Necessary?
The previous RDAs and Recommended Nutrient Intakes did not include
recommended intakes for indispensable amino acids; it was assumed that
individuals consuming a mixed diet with recommended amounts of pro-
tein would obtain required amounts of indispensable amino acids. In other
words, it was not necessary to assess or plan for intakes of indispensable
amino acids. Now that EARs and RDAs have been provided for indispens-
able amino acids, it is important to re-examine the question: Is it necessary
to consider indispensable amino acids when conducting dietary planning
and assessment, or is it sufficient to consider only total protein?
The simplest scenario for answering this question relates to dietary
planning for individuals. When planning for individuals, the objective is to
meet the RDA, as doing so ensures a very low risk of inadequacy. Thus, do
diets that provide the RDA for protein also provide the RDAs for indis-
pensable amino acids? It appears that this may not necessarily occur, at
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least for the amino acid lysine. Data in Table 13-2 suggest that although
most protein sources provide recommended amounts of threonine,
tryptophan, and sulfur-containing amino acids, this is not true for lysine.
Animal protein sources provide recommended intakes of lysine, but it is
clear that individuals who do not consume animal protein sources, or who
consume limited amounts, would be unlikely to obtain the recommended
amounts of lysine when total protein intake is equal to the RDA, unless
their diets were usually high in beans or other legumes. Even then, diets
could be marginal, as the data in Table 13-2 regarding amino acid compo-
sition do not account for the apparent lower digestibility of some plant
protein sources. Beans, for example, have a digestibility of 82 percent
relative to milk and meat. Thus, it appears that, in addition to assessing
and planning total protein intakes, it is also necessary to assess and plan
for intakes of the amino acid lysine in individuals consuming proteins with
low levels of lysine.
TABLE 13-2 Selected Indispensable Amino Acid Content of
Protein Sources Compared with Recommended Levels
Indispensable Amino Acid (mg/g protein)
Sulfur
Lysine Threonine Tryptophan Amino Acids
Scoring pattern, adult 47 24 6 23
FNB/IOM Recommended 51 27 7 25
Protein Scoring Pattern
(Child 1–3 y)
Canadian diet, 1984 61 38 12 34
U.S. diet, 1977 68 39 12 35
28a
Wheat bread 30 13 39
26a
Garbanzo beans 67 37 10
Beef 83 44 11 37
Cheddar cheese 76 33 12 29
Tofu 66 41 16 27
38a
Brown rice 37 13 35
29a 25a
Almonds 32 15
36a
Peanut butter 34 10 33
28a
Cornmeal 38 7 39
a The amino acid content in these foods is lower than the proportion recommended
for the proper balance of indispensable amino acids in the total diet, based on the
FNB/IOM Recommended Protein Scoring Pattern (Table 10-26). Thus a mixed diet
containing a variety of protein sources is recommended.
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As alluded to above, the need to plan and assess intakes of lysine is
likely of greatest importance for individuals whose diets emphasize plant
foods and are relatively low in total protein. For example, consider a
woman who weighs 57 kg and follows a plant-based diet that provides the
RDA for total protein (in her case, 57 × 0.8 g/kg = 45 g/day). She would
be unlikely to meet her RDA for lysine (2.2 g/day) unless 50 percent or
more of her dietary protein was provided from beans or tofu (rich sources
of lysine). To be specific, 23 g of protein from beans and tofu would
provide about 1.5 g of lysine, and 22 grams of protein from other sources,
such as wheat, rice and nuts, would provide about 0.7 g of lysine. However,
if her total protein intake was higher, (e.g., about 63 g/day, close to the
median protein intake of women reported in the CSFII survey [Appendix
Table E-16]), she could meet her RDA for lysine with much smaller
amounts of beans and tofu.
INTEGRATED EXAMPLE
The preceding discussion illustrates that there are many considerations
involved in dietary assessment and planning for energy and macronutrients.
The example that follows illustrates how these considerations might be
addressed in planning the macronutrient intake of an individual. Let us
assume that the individual is a 35-year-old woman, 1.68 m in height, and
weighing 69 kg. Her job is not physically active, and she does little planned
exercise, so it might appear that activity level would be classified as sedentary.
However, to provide a more reliable indication of her activity level, she
keeps a 7-day record of her activities using a chart similar to that provided
in Chapter 12 (Table 12-3), and this also confirms that she is sedentary.
Energy
Because recommended intakes of at least some nutrients relate to
energy requirements, the first step would be to estimate her energy expen-
diture. Her BMI is 24.4, so the equation for normal-weight adults would be
used. Assuming it was appropriate to maintain her current weight and
activity level, the Estimated Energy Requirement for a woman with her
characteristics would be about 2,000 kcal/day. Of course, her individual
energy expenditure could be above or below this amount, but it provides a
starting point. An additional consideration would be that her current
activity level is less than the recommended of “active.” If her energy needs
were estimated based on being “active,” the estimate would be 2,150 kcal,
and other values listed below would change proportionally.
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Fatty Acids
The AI for n-3 polyunsaturated fatty acid (α-linolenic acid) is 1.1 g/day,
and the AI for n-6 polyunsaturated fatty acid (linoleic acid) is 12 g/day.
Therefore, her diet should provide these levels of fatty acids, which would
provide 9.9 and 108 kcal/day from n-3 and n-6 fatty acids, respectively,
toward her total energy intake. Longer-chain polyunsaturated n-3 (approxi-
mately 10 percent) and n-6 fatty acids can contribute toward this AI.
Protein
The RDA for protein is 0.8 g/kg/day, so her recommended intake
would be 55 g/day (69 kg × 0.8 g/kg), which would provide 220 kcal/day.
In addition, she would need to meet recommended intakes of indispens-
able amino acids, of which lysine is most likely to be limiting. Her recom-
mended lysine intake would be 38 mg/kg/day, or approximately 2.6 g/day.
Carbohydrate and Total Fiber
The RDA for carbohydrate for adult women is 120 g/day, which is
equivalent to 480 kcal/day. More than 120 g/day will probably be needed
to assure adequate energy consumption within the AMDR for carbo-
hydrate. The AI for Total Fiber is 25 g/day and her diet should be planned
to provide for this level of intake. The contribution of Total Fiber to energy
(kcal/g) intake is still unclear.
Energy Distribution
The amount of energy provided by the recommended intakes of es-
sential fatty acids, protein, and carbohydrate totals only 818 kcal/day, yet
her estimated requirement is approximately 2,000 kcal/day. Her energy
intake might be allocated among macronutrients as shown in Table 13-3
for an overall healthy diet.
Because the estimated energy expenditure of 2,000 kcal/day may differ
from actual energy expenditure (and lead to changes in weight that may
not be desirable), her weight should be monitored over time and energy
intake adjusted as appropriate.
SUMMARY
The Dietary Reference Intakes (DRIs) may be used to assess nutrient
intakes as well as to plan nutrient intakes. Box 13-1 summarizes the appro-
priate uses of the DRIs for individuals and groups.
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TABLE 13-3 Example of Macronutrients in a 2,000 kcal Diet
Range Selected Amount
for 2,000 Amount (% for 2,000 Energy for
AMDRa (%)
Nutrient kcal (g) of energy) kcal (g) 2,000 kcal
Fat 20–35% 44–78 30 67 g 600 kcal
n -3 PUFAb 0.6–1.2% 1.3–2.7 0.8 1.8 g 16 kcal
(as part of (as part of
total fat) total fat)
n -6 PUFA 5–10% 11–22 7 16 g 144 kcal
(as part of (as part of
total fat) total fat)
Protein 10–35% 50–175 15 75 g 300 kcal
Carbohydrate 45–65% 225–325 55 275 g 1,100 kcal
a AMDR = Acceptable Macronutrient Distribution Range.
b PUFA = polyunsaturated fatty acid.
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966 DIETARY REFERENCE INTAKES
BOX 13-1
Uses of Dietary Reference Intakes for Healthy Individuals and Groups
For the Individual a For a Group b
Type of Use
EARc: Use to examine the prob-
Assessment EAR: Use to estimate the preva-
ability that usual intake is inad- lence of inadequate intakes
equate. within a group.
RDA: Usual intake at or above RDA: Do not use to assess in-
this level has a low probability takes of groups
of inadequacy.
AId: Mean usual intake at this
AId: Usual intake at or above level implies a low prevalence
this level has a low probability of inadequate intakes.
of inadequacy.
UL: Use to estimate the per-
UL: Intake above this level has centage of the population at
a potential risk of adverse ef- potential risk of adverse effects
fects. from excess nutrient intake.
RDAe : Aim for this intake. EARe: Use to plan an intake dis-
Planning
tribution with a low prevalence
AId: Aim for this intake. of inadequate intakes.
AId: Use to plan mean intakes.
UL: Use as a guide to limit in-
take; chronic intake of higher
amounts may increase the po- UL: Use to plan intake distribu-
tential risk of adverse effects. tions with a low prevalence of
intakes potentially at risk of ad-
verse effects.
a Requires accurate measure of usual intake. Evaluation of true status requires clinical, biochemi-
cal, and anthropometric data.
b Requires statistically valid approximation of distribution of usual intakes.
c Requires information on the variability of day-to-day intake and the variability of the require-
ment.
d For the nutrients in this report, AIs are set for infants for all nutrients, and for other age groups
for Total Fiber and for n-3 and n-6 polyunsaturated fatty acids. The AI may be used as a guide for
infants as it reflects the average intake from human milk. Infants consuming formulas with the
same nutrient composition as human milk consume an adequate amount after adjustments are
made for differences in bioavailability. In the context of assessing groups, when the AI for a
nutrient is not based on mean intakes of a healthy population, this assessment is made with less
confidence.
e In the case of energy, an Estimated Energy Requirement (EER) is provided; it is the dietary
energy intake that is predicted (with variance) to maintain energy balance in a healthy adult of
defined age, gender, weight, height, and level of physical activity, consistent with good health. In
children and pregnant and lactating women, the EER is taken to include the needs associated with
the deposition of tissues or the secretion of milk at rates consistent with good health. For individu-
als, the EER represents the midpoint of a range within which an individual’s energy requirement is
likely to vary. As such, it is below the needs of half the individuals with specified characteristics and
exceeds the needs of the other half. Body weight should be monitored and energy intake adjusted
accordingly.
NOTE: RDA = Recommended Dietary Allowance, EAR = Estimated Average Requirement, AI =
Adequate Intake, UL = Tolerable Upper Intake Level.
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Representative terms from entire chapter:
energy expenditure
