Implementing food-based dietary guidelines for - United Nations ...

Establishing nutrient intake values
have been gathered on responses to various levels of
intake (see box 1). This paper covers the first two of
these steps in detail.
Step 1: Determine average nutrient
requirement (ANR)
The first step in developing an NIV is to determine
the average nutrient requirement (ANR) for the target
population group. Although this sounds simple, it is
very complex and is a critical step in developing usable
nutrient intake values. It requires that the available data
fit the model described by King et al. [1] and Murphy
and Vorster [2] in this issue.
As described by King et al. [1], the model for setting
NIVs has been adopted over the last two decades in
whole or in part by a number of countries and regions
for use in nutrition policy development and programs.
The framework described in King et al. [1] proposes
harmonizing the terms used for the various values
as well as their definitions in order to move toward
adoption, where appropriate, of common NIVs. The
model requires the determination of an ANR for a
defined subset of the apparently healthy population.
From information that relates meeting an individual’s
requirement to the level of nutrient intake consumed,
an individual nutrient level (INL x ) is derived that
should meet the needs of a defined percentage (which
is represented by the subunit x) of that subgroup in the
population. More information on the model and its
statistical basis and assumptions is provided by Murphy
and Vorster [2].
If it were possible to know each person’s usual
requirement based on a chosen criterion for adequacy,
it would be possible to identify an intake amount that
is the average (median) requirement of the group of
interest. With this information, and with information
on each person’s usual intake, it is also possible to use
BOX 1. Steps in applying criteria to establish an individual
nutrient level (INL)
1. Determine average (median) nutrient requirements
(ANR) for target population subgroup
a. Evaluate possible requirement datasets
b. Determine usable dataset based on chosen level
of adequacy
2. Estimate variation in requirements in target population
group
3. Increase the ANR by a factor based on the variation
observed or assumed (e.g., 2 x CV ANR ) to obtain
INL x , the nutrient intake to be used as a goal for
individuals (see Murphy and Vorster [2])
4. Determine the nutrient intake values (NIVs) for
other population groups with missing data (see
Atkinson and Koletzko [4] in this issue)
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the ANR as the cutoff for the percentage of the population
whose diet is inadequate for a given nutrient [5] in
order to establish the prevalence of inadequacy for the
population group of interest (see Murphy and Vorster
[2] for more information).
Adequate for what?
A number of assumptions must be made when estimating
an ANR. Since the ANR plays a key role both in
assessing adequacy of the nutrient intakes of groups
and in serving as the basis for a recommended nutrient
intake for individuals (INL x ) (see Murphy and Vorster
[2]), it becomes very important to carefully examine
the data used to establish the ANR to ensure that the
ANR is both applicable to the group and based on the
best indicator of adequacy that can be applied.
The effects of inadequacy become apparent when
diets are low in or lack a nutrient required for normal
physiological function, or when dietary intakes result
in increasing the risk of onset of a chronic disease such
as cardiovascular disease; with greater deprivation,
more serious effects are frequently demonstrated. Correspondingly,
after a period of depletion, when small
amounts of a nutrient are then provided, some functions
may be restored while others remain abnormal
and are not reversed. For many nutrients, this results
in a continuum of responses observed as levels of
intake increase, and may range from easily observed
deficiency signs and symptoms when the diet lacks the
nutrient (such as is seen in scurvy with chronic and
severe lack of vitamin C) to subtle changes indicating
suboptimal levels of intake, such as a decrease in the
ability to respond to oxidative stress as measured by
leukocyte ascorbate concentrations. Table 1 provides a
list of the types of research studies and criteria that can
and have been used to determine what is “adequate” for
various nutrients.
The possible types of criteria and their indicators can
be grouped on the basis of their origins, as biochemical
measures (e.g., red blood cell folate), physiological
measures (e.g., blood pressure), functional measures
(e.g., dark adaptation), equilibrium maintenance (e.g.,
factorial estimates of iron), disease incidence (e.g., cardiovascular
disease), or animal models of inadequacy
(e.g., hemolytic anemia in rats).
Model indicators or criteria for adequacy
To serve as a model indicator or criterion of adequacy,
an indicator should meet the following criteria:
» It can be measured without compromising the health
or well-being of the individual (thus somewhat noninvasive,
particularly for infants and children);
» It does not fluctuate rapidly or markedly when intake
is increased or reduced, so that changes in it reflect
the gradual nature of a change in availability of the