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

Establishing nutrient intake values
each person in a population group. With the growing
problem of obesity and overweight, it is more difficult
to determine what the mean energy intake of a group
should be to meet the requirements of all members of
the group, yet not result in overconsumption by some.
Unlike the use of average population intakes for nutrients
in apparently healthy populations as surrogates for
an INL x where dose–response data are not available,
average energy intakes cannot be used, as most populations
in both developed and developing countries
are now experiencing adverse effects associated with
excess consumption of energy, inadequate physical
activity, or both.
Methods of estimating energy requirements
Similar to nutrients, energy requirements measured
in individuals with similar characteristics, such as
age, body size, sex, and physical activity levels, vary;
the variation seen in observed requirements assumes
a normal distribution. When energy expenditure
over time (e.g., 2 to 3 weeks) is measured carefully
in a sample of individuals whose characteristics are
known, it is possible to develop estimates of energy
requirements for the group, along with a measure of
the variance in those requirements among the individuals
in the sample. These requirement distributions
have been used to predict the requirements for other
individuals with similar characteristics. One of the
advances in the ability to develop good predictions of
energy requirements is the ability now to use tracer
methodology, such as doubly labeled water, to obtain
independent estimates of energy expenditure without
perturbing the environment of the individual [10].
Older methods estimated expenditure indirectly (e.g.,
metabolic hoods) or estimated food intake and derived
the amount of energy consumed, equating it with the
amount expended.
Components of energy requirements
As outlined in the definition of energy requirements,
the energy required for five general components makes
up the total human energy requirement: basal metabolism,
metabolic response to food, physical activity,
growth, and needs during pregnancy and lactation.
Early studies of energy requirements, in which the
method used to estimate energy expenditure itself
influenced the energy requirement, often involved
estimating each of these individually and summing
the total to get the total energy required. With the
advent of doubly labeled water, prediction equations
that take into account all of these energy components
have been developed. Recently, doubly labeled water
has been used as well to validate other methods to estimate
energy requirements that are less expensive and
more adaptable to different settings, such as heart-rate
monitoring [24].
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Equations that are derived from these data depend
on the accuracy of the method employed and the extent
to which variables in energy expenditure are included
as identified factors that influence energy requirements.
Sex, age, body weight (or body mass index
[BMI]), and level and types of physical activity have
been found to have the greatest effect on total energy
requirements [10, 24].
Prediction equations now available are useful as
initial estimates of energy requirements for other
similar population groups, assuming that the information
about the population subgroup (i.e., age, body
weight [BMI], and activity level) is known. Prediction
(regression) equations developed to date have
estimates of variation as well, and these provide the
ranges (representing expected variation) that would
be predicted in actual requirements as compared with
the point estimates obtained from the regression equations
[10, 24].
Use of prediction equations as NIVs
Tables have been constructed that translate the prediction
equations into estimates of energy requirements
by age, sex, physical activity, and/or body weight;
these can be applied to other population groups after
adjustment for known differences in physical activity,
body size, and other variables that may not be included
in the tables. Information on how best to use the data
and information is provided in the reports [10, 24] that
have developed the prediction equations and should be
used as a starting point for group-specific estimates of
energy requirements.
Summary
In establishing nutrient intake values (NIVs) to meet
requirements (and usually for excess intakes), it is
important to specify the criterion or indicator of adequacy
or excess that is selected and to be transparent in
the dataset used to set the NIV. For almost all nutrients
studied to date, there exists a continuum of definable
functions, most of which are impaired at low levels of
intake, whereas at high levels of intake all appear to
function normally or to be within the normal range.
Choice of the indicator will dictate the amount of the
nutrient that meets an individual’s requirement, as
defined by that indicator. Datasets from dose–response
studies in which nutrients at multiple levels (at least
three) are given to the same individuals and in which at
least one level results in measured abnormal responses
or functions are important to serve as the basis for
determining average nutrient requirements (ANRs).
Of equal if not greater importance is the distribution
of requirements in a group; variation in requirements
can be due to differences in metabolism, but also to
differences in environment and diet. A key component