Livro DRI 2006 (Micronutrientes)

Livro DRI 2006 (Micronutrientes)


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within a group are not normally distributed. Therefore, the
SDusual intake cannot be used to identify the position of the target usual nutrient
intake distribution. Instead, the necessary approach is similar in principle to
the one in the previous section, although it does not depend on the SD of usual
intake and a z-score. A practitioner would first specify the acceptable preva-
lence of inadequate intake, and then position the usual intake distribution so
Copyright © National Academy of Sciences. All rights reserved.
Dietary Reference Intakes: The Essential Guide to Nutrient Requirements
http://www.nap.edu/catalog/11537.html
52 DRIs: THE ESSENTIAL GUIDE TO NUTRIENT REQUIREMENTS
that the percentile of usual intake associated with this specified prevalence of
inadequate intake equals the EAR.
Using the DRIs to Plan a Group\u2019s Nutrient Intakes
The summary below explains how DRIs are appropriately used in planning a
group\u2019s nutrient intakes. Further details are provided in the sections that follow
and in the case studies at the end of the chapter.
\u2022 For nutrients with an EAR and RDA, the EAR is used in conjunction
with the usual nutrient intake distribution to plan for an acceptably low
prevalence of inadequate intakes within the group. For most nutrients,
the planning goal is to minimize the prevalence of intakes below the
EAR. The RDA is not recommended for use in planning the nutrient
intakes of groups.
\u2022 For nutrients without an EAR, the AI is used instead. The AI is used as
the target for the mean, or median, intake of the group. The goal is to
increase the group\u2019s mean or median intake to the level of the AI.
\u2022 For nutrients with a UL, this value is used to plan for an acceptably low
prevalence of intakes at risk of being excessive.
\u2022 For nutrients with an AMDR, an additional goal of planning is to achieve
a macronutrient distribution in which the intakes of most of the group
fall within the AMDRs.
\u2022 For energy, the goal is for the group\u2019s mean intake to equal the EER. For
energy, the estimated energy requirement of a reference individual or an
average of estimated maintenance energy needs for the group members
can be used in planning energy intake of groups.
USING THE EAR TO PLAN A GROUP\u2019S NUTRIENT INTAKES
For nutrients that have an EAR, this value is used in conjunction with the usual
nutrient intake distribution to plan for an acceptably low prevalence of inad-
equate intakes within the group. For most nutrients, the planning goal is to
minimize the prevalence of intakes below the EAR.
USING THE AI TO PLAN A GROUP\u2019S NUTRIENT INTAKES
Due to limitations in available data, the AIs for various nutrients are set using
different criteria. For some nutrients, the AI is based on the observed mean or
median intakes by groups that are maintaining health and nutritional status
consistent with meeting requirements. In these cases, the AI is conceptually
similar to the median of a target usual nutrient intake distribution. For other
nutrients, the AI is the level of intake at which subjects in an experimental
Copyright © National Academy of Sciences. All rights reserved.
Dietary Reference Intakes: The Essential Guide to Nutrient Requirements
http://www.nap.edu/catalog/11537.html
PART I: APPLYING THE DIETARY REFERENCE INTAKES 53
study met the criterion of adequacy. In these cases, the AI is not directly compa-
rable to a target median intake.
Because of these differences in how the AI is set for different nutrients, the
appropriate use of the AI in planning group intakes also varies. The AI can be
used if the variability in the usual intake of the population being planned for is
similar to the variability in intake of the healthy population that was used to set
the AI. In this case, the appropriate use of the AI would be as the target median
intake of the group.
However, if the AI is not based on a group mean or median intake of a
healthy population, practitioners must recognize that there is a reduced level of
confidence that achieving a mean or median intake at the AI will result in a low
prevalence of inadequacy. In addition, the AI cannot be used to estimate the
proportion of a group with inadequate intakes. Thus, regardless of how the AI
has been estimated, it is not possible to use the AI to plan a target distribution
of usual intakes with a known prevalence of inadequacy. Table 4 presents a
summary of the nutrients for which AIs have been estimated and notes the
cases in which these estimates reflect experimental derivation and observed
TABLE 4 Method Used to Estimate Adequate Intake (AI) for
Groups of Healthy Adults
Estimation Method Nutrient
Experimental derivation Biotin
Calcium
Choline
Vitamin D
Fiber, total
Fluoride
Potassium
Sodium and chloride
Mean intake Chromium
Median intake Vitamin K
Manganese
Pantothenic acid
n-6 Polyunsaturated fatty acids
n-3 Polyunsaturated fatty acids
Water, total
Copyright © National Academy of Sciences. All rights reserved.
Dietary Reference Intakes: The Essential Guide to Nutrient Requirements
http://www.nap.edu/catalog/11537.html
54 DRIs: THE ESSENTIAL GUIDE TO NUTRIENT REQUIREMENTS
mean and median intake of healthy groups. Practitioners who want to compare
their target groups to the groups used to set the AIs can obtain this information
in each of the individual nutrient profiles found in Part III.
USING THE UL TO PLAN A GROUP\u2019S NUTRIENT INTAKES
For nutrients that have a UL, the planning goal is to achieve an acceptably low
prevalence of intakes above the UL.
USING THE EER TO PLAN A GROUP\u2019S DIET
As is true for individuals, the underlying objective in planning the energy in-
take of a group is similar to planning intakes for other nutrients: to attain an
acceptably low prevalence of inadequacy and potential excess. When planning
the energy intakes of groups, the goal is for the group\u2019s mean intake to equal the
EER. Because energy intake is related to energy requirement, it is assumed that
people in the group with energy requirements above the EER will choose en-
ergy intakes that are above the EER, and those with requirements below the
EER will choose intakes below the EER, so that the average intake will equal the
EER.
The EAR cut-point approach should not be used for planning energy in-
takes, because it is expected, and desirable, for half of the group to have intakes
below the EER.
There are two possible approaches to estimate energy intakes of groups.
One can estimate energy requirements for the reference person or obtain an
average of estimated maintenance energy needs for the group members. For
example, to plan for a large group of men aged 19 through 30 years, one can
estimate the EER for the reference male with a weight of 70 kg (154 lbs) and a
height of 1.76 m (~ 5 ft 8 in) and who is considered low active, and use this
number (~ 2,700 kcal) as the target for the group. This approach would re-
quire the assumption that all members of the group were similar to the refer-
ence person or that the reference person accurately represented the group\u2019s
average values for age, height, weight, and activity level, and that these vari-
ables were symmetrically distributed.
The preferred approach would be to plan for an intake equal to the average
energy expenditure for the group. For example, assuming that there is access to
data on height, weight, age, and activity level, the energy expenditure for each
individual in the group could be estimated. The average of these values would
then be used as the planning goal for the maintenance of the group\u2019s current
weight and activity level. As with other planning applications, assessing the
plan for a group\u2019s energy intake, following its implementation, would lead to
further refinements. In the case of energy, however, assessment would be based
on monitoring body weight rather than on