Livro DRI 2006 (Micronutrientes)

Livro DRI 2006 (Micronutrientes)


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as a goal for daily intake by individuals. In the case of energy, an estimated
energy requirement called the Estimated Energy Requirement (EER) is provided.
Recommended Dietary Allowance
The Recommended Dietary Allowance (RDA) is an estimate of the daily average
dietary intake that meets the nutrient needs of nearly all (97\u201398 percent) healthy
members of a particular life stage and gender group. The RDA thus exceeds the
requirements of nearly all members of the group. It can be used as a guide for
daily intake by individuals, and because it falls above the requirements of most
people, intakes below the RDA cannot be assessed as being inadequate. Usual
intake at the RDA should have a low probability of inadequacy.
If an EAR cannot be set due to data limitations, no RDA will be calculated.
For nutrients that have a statistically normal requirement distribution, the RDA
is set by adding two standard deviations (SD) to the EAR. Thus,
RDA = EAR + 2SD
For nutrients with skewed requirement distributions (most notably, iron in
menstruating women) the RDA is set between the 97th and 98th percentile of
the requirement distribution. (See Part I, \u201cApplying the Dietary Reference In-
takes\u201d for more information on calculating RDAs when nutrient requirements
are skewed.)
Adequate Intake
If sufficient or adequate scientific evidence is not available to establish an EAR
and thus an RDA, an AI is usually derived for the nutrient instead. An AI is
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: INTRODUCTION TO THE DIETARY REFERENCE INTAKES 11
based on fewer data and incorporates more judgment than is used in establish-
ing an EAR and subsequently the RDA. The setting of an AI usually indicates
that more research is needed to determine, with some degree of confidence, the
mean and distribution of requirements for that specific nutrient.
The AI is a recommended average daily nutrient intake level based on ob-
served or experimentally determined approximations or estimates of nutrient
intake by a group (or groups) of apparently healthy people who are assumed to
be maintaining an adequate nutritional state. Examples of adequate nutritional
states include normal growth, maintenance of normal levels of nutrients in
plasma, and other aspects of nutritional well-being or general health.
The AI is expected to meet or exceed the needs of most individuals in a
specific life stage and gender group. When an RDA is not available for a nutri-
ent (because an EAR could not be developed), the AI can be used as the guide
for an individual\u2019s intake. However, the AI has very limited uses in assessments
of any type.
Tolerable Upper Intake Level
The Tolerable Upper Intake Level (UL) is the highest average daily nutrient
intake level likely to pose no risk of adverse health effects for nearly all people
Acceptable Macronutrient Distribution Ranges (AMDR)
A growing body of evidence indicates that an imbalance in macro-
nutrients (e.g., low or high percent of energy), particularly with certain
fatty acids and relative amounts of fat and carbohydrates, can increase
risk of several chronic diseases. Based on this evidence, Acceptable
Macronutrient Distribution Ranges (AMDRs) have been estimated for in-
dividuals. An AMDR is the range of intakes of an energy source that is
associated with a reduced risk of chronic disease, yet can provide ad-
equate amounts of essential nutrients.
The AMDR is expressed as a percentage of total energy intake. A
key feature of each AMDR is that it has a lower and upper boundary. For
example, the AMDR for carbohydrates ranges from 45 to 65 percent of
total energy intake. Intakes that fall below or above this range increase
the potential for an elevated risk of chronic diseases. Intakes outside of
the range also raise the risk of inadequate consumption of essential nutri-
ents. The AMDRs are discussed in more detail in Part II, \u201cMacronutrients,
Healthful Diets, and Physical Activity.\u201d
Copyright © National Academy of Sciences. All rights reserved.
Dietary Reference Intakes: The Essential Guide to Nutrient Requirements
http://www.nap.edu/catalog/11537.html
12 DRIs: THE ESSENTIAL GUIDE TO NUTRIENT REQUIREMENTS
in a particular group. As intake increases above the UL, the potential risk for
adverse effects increases. The need for setting a UL grew out of two major trends:
increased fortification of foods with nutrients and the use of dietary supple-
ments by more people and in larger doses.
The UL is not a recommended level of intake, but rather the highest intake
level that can be tolerated without the possibility of causing ill effects. The value
applies to chronic daily use and is usually based on the total intake of a nutrient
from food, water, and supplements if adverse effects have been associated with
total intake. However, if adverse effects have been associated with intake from
supplements or food fortificants alone, the UL is based on the nutrient intake
from one or both of these sources only, rather than on total intake.
For some nutrients, not enough data were available to set a UL. However,
this does not mean that consuming excess amounts poses no risks. Instead, it
indicates a need for caution in consuming large amounts. See Figure 1 for a
visual relationship between the DRIs.
PARAMETERS USED IN DEVELOPING DRIS
The DRIs presented in this publication apply to the healthy general population.
In addition, DRI values are assigned to life stage groups that correspond to
FIGURE 1 Relationship between Dietary Reference Intakes. This figure shows that the
Estimated Average Requirement (EAR) is the intake at which the risk of inadequacy is 0.5 (50
percent) to an individual. The Recommended Dietary Allowance (RDA) is the intake at which
the risk of inadequacy is very small\u2014only 0.02 to 0.03 (2 to 3 percent). The Adequate Intake
(AI) does not bear a consistent relationship to the EAR or the RDA because it is set without
the estimate of the requirement. At intakes between the RDA and the Tolerable Upper Intake
Level (UL), the risks of inadequacy and of excess are both close to zero. At intakes above the
UL, the risk of adverse effects may increase.
EAR
RDA UL
0.0
0.5
1.0
0.0
0.5
1.0
Observed Level of Intake
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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: INTRODUCTION TO THE DIETARY REFERENCE INTAKES 13
various periods of the human lifespan. Reference heights and weights for life
stage and gender groups were used for extrapolations performed on the basis of
body weight or size. They also indicate the extent to which intake adjustments
might be made for individuals or population groups that significantly deviate
from typical heights and weights.
Applicable Populations
An important principle underlying the DRIs is that they are standards for ap-
parently healthy people and are not meant to be applied to those with acute or
chronic disease or for the repletion of nutrient levels in previously deficient
individuals. Meeting the recommended intakes for the nutrients would not nec-
essarily provide enough for individuals who are already malnourished, nor would
they be adequate for certain disease states marked by increase nutrient require-
ments. Although the RDA or AI may serve as the basis for specialized guidance,
qualified medical and nutrition personnel should make the needed adjustments
for individuals with specific needs.
Life Stage Groups
Where data were available, DRIs were divided into 12 life stage groups