Livro DRI 2006 (Micronutrientes)

Livro DRI 2006 (Micronutrientes)


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6 7
 
0 1 2 3 4 5 6 7
AI
AIMedian intake
Median intake
Distribution of
usual intakes
Distribution of
usual intakes
Theoretical
requirement
distribution
Theoretical
requirement
distribution
Nutrient X (mg/d)
Nutrient X (mg/d)
Panel A
Panel B
FIGURE 3 Overlap of requirement and intake distributions varies.
estimate the degree of confidence that an individual\u2019s intake meets his or her
requirement. There are also equations that have been developed to estimate the
degree of confidence that an individual\u2019s intake is above the AI, and below the
Tolerable Upper Intake Level (UL).
It is important to keep in mind that the DRIs are estimates based on avail-
able data, and that even when an EAR, RDA, and UL for a nutrient are provided
for a life stage and gender group, there is considerable uncertainty about these
values. Because information on both dietary intakes and requirements are esti-
mated, it is very difficult to exactly determine whether an individual\u2019s diet meets
his or her individual requirement, even with the statistical approaches described
Copyright © National Academy of Sciences. All rights reserved.
Dietary Reference Intakes: The Essential Guide to Nutrient Requirements
http://www.nap.edu/catalog/11537.html
26 DRIs: THE ESSENTIAL GUIDE TO NUTRIENT REQUIREMENTS
in this chapter. Thus, assessment of dietary intakes should be used as only one
part of a nutritional assessment, and the results must be kept in context. Nutri-
ent intake data should always be considered in combination with other infor-
mation, such as anthropometric measurements, biochemical indices, diagnoses,
clinical status, and other factors. Dietary adequacy should be assessed and diet
plans formulated based on the totality of evidence, and not on dietary intake
data alone.
ESTIMATING AN INDIVIDUAL\u2019S USUAL INTAKE AND REQUIREMENT
To conduct a dietary assessment, information is needed on both dietary intakes
and dietary requirements. Information on dietary intake of individuals is usu-
ally gathered through food records or dietary recalls, and the requirement esti-
mate is provided through the DRI process. In all cases the individual\u2019s usual
intake and true requirement can only be approximated.
Estimation of Usual Intake
Obtaining accurate information on dietary intakes is challenging for a num-
ber of reasons, including the accuracy of dietary assessment techniques, as well
as the challenges related to variability in intakes. The strongest methods for
dietary assessment of nutrient adequacy are 24-hour recalls, diet records, or
quantitative diet histories. Even so, the literature indicates that a sizeable pro-
portion of individuals systematically misreport their dietary intakes, with the
tendency toward underreporting (particularly for energy and percentage of en-
ergy from fat). It is unclear how this affects the accuracy of self-reported intakes
of nutrients. Well-accepted, validated methods to statistically correct for the
effects of underreporting are presently lacking.
There is also large day-to-day variation within a given individual\u2019s intake
due to factors such as variation in appetite, food choices, day of the week, and
season. The result is that the calculation of dietary intake from one or even
several days of intake may give an inaccurate estimate of that individual\u2019s usual
nutrient intake, especially if food choices vary greatly from one day to the next.
Thus, observed dietary intake is probably not the same as the long-term usual
intake of an individual. However, the observed mean intake is still the best
available estimate of dietary intake, and can still be used providing that it is
recognized there is an amount of variability associated with that best estimate.
Estimation of Requirement
It is nearly impossible to determine what an individual\u2019s exact requirement
for a nutrient is, unless that individual has participated in a requirement study.
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 27
Therefore, the fall-back assumption is that the individual\u2019s requirement will be
close to the average, in which case the EAR is the best estimate for an individual\u2019s
unobservable requirement. It is important to note that there is variation in nu-
trient requirements between different individuals, and this needs to be taken
into account when conducting an assessment.
Using a Qualitative Approach to Assess an Individual\u2019s
Nutrient Intake
Many users of the DRIs may find a qualitative assessment of an individual\u2019s
nutrient intakes to be useful. When conducting this type of descriptive assess-
ment, it is important to keep in mind the limitations associated with the estima-
tion of both intakes and requirements.
For nutrients with an EAR and RDA:
\u2022 Observed mean intake below the EAR very likely needs to be improved
(because the probability of adequacy is 50 percent or less).
\u2022 Observed mean intake between the EAR and the RDA probably needs
to be improved (because the probability of adequacy is more than 50
percent but less than 97.5 percent).
\u2022 Intakes below the RDA cannot be assumed to be inadequate because the
RDA by definition exceeds the actual requirements of all but 2\u20133 per-
cent of the population; many with intakes below the RDA may be meet-
ing their individual requirements.
\u2022 The likelihood of nutrient inadequacy increases as usual intake falls
further below the RDA.
\u2022 Only if intakes have been observed for a large number of days and are at
or above the RDA should one have a high level of confidence that the
intake is adequate.
For nutrients with an Adequate Intake (AI):
\u2022 If observed mean intake equals or exceeds the AI, it can be concluded
that the diet is almost certainly adequate.
\u2022 If, however, observed mean intake falls below the AI, no estimate can be
made about the probability of nutrient inadequacy.
\u2022 Professional judgment, based on additional types of information about
the individual, should be exercised when interpreting intakes below
the AI.
Copyright © National Academy of Sciences. All rights reserved.
Dietary Reference Intakes: The Essential Guide to Nutrient Requirements
http://www.nap.edu/catalog/11537.html
28 DRIs: THE ESSENTIAL GUIDE TO NUTRIENT REQUIREMENTS
For nutrients with a UL:
\u2022 Observed mean intake less than the UL is likely to be safe.
\u2022 Observed mean intake equal to or greater than the UL may indicate a
potential risk of adverse effects. The higher the intake in comparison to
the UL, the greater the potential risk.
For nutrients with an Acceptable Macronutrient Distribution Range (AMDR):
\u2022 Observed mean intake between the lower and upper bound of the AMDR
is within the acceptable range.
\u2022 Observed mean intake below the lower bound or above the upper bound
of the AMDR may heighten concern for possible adverse consequences.
For energy:
\u2022 Body mass index (BMI) should be used to assess the adequacy of energy
intake, rather than a comparison to the Estimated Energy Requirement
(EER).
Using a Quantitative Approach to Assess an
Individual\u2019s Nutrient Intake
An approach has been developed that statistically estimates the level of confi-
dence that an individual\u2019s usual intake is above an individual\u2019s requirement, or
below the UL. The equations developed for the assessment of individuals are
based on the principles of hypothesis testing and levels of confidence based on
a normal distribution curve.
The equations proposed here are not applicable to all nutrients because
they assume a normal distribution of daily intakes and requirements. For nutri-
ents for which a