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

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TABLE 1. Possible criteria that may serve as the basis for adequacy
Type of study Measurement Examples a
Nutrition intervention studies (randomized,
placebo-controlled studies)
nutrient at the cellular level;
» It has been validated as representative of the functional
level present of the nutrient and not easily
altered by other environmental changes, including
the dietary content of other nutrients.
In the case of chronic disease relationships or developmental
abnormalities, a surrogate marker of adequacy
is useful because while the initiation of the
disease process or abnormality may occur as a result of
an alteration in nutrient intake (either not enough or
too much) at an early age, the presence of the chronic
disease may not be evident functionally for many years
via observable clinical signs or symptoms. The surrogate
marker, then, must be validated through strong
correlation with both the dietary constituent and with
subsequent development of the disease in order to be
considered a true indicator of adequacy. The generally
accepted example of a validated surrogate marker is
serum cholesterol and subsequent development of
cardiovascular disease.
None of the possible criteria used in establishing
nutrient requirements and listed in table 1 is considered
a perfect example of a model indicator of
adequacy, although some are better choices, when
available, than others.
Selecting criteria for setting nutrient standards
The values of the ANR and thus the INL x depend
on which criterion is selected to establish adequacy.
Nutrient adequacy is not well defined, and in some
situations it may become a political decision. It is well
known that 10 mg of vitamin C or less per day will
prevent scurvy. If the criterion chosen for vitamin C
adequacy is prevention of scurvy, then the ANR will
Functional outcome Calcium fracture rate with increased
calcium intake via supplements or
placebo
Biochemical measurements Red blood cell folate response to varying
levels of folate
Depletion/repletion studies Biochemical measurements Leukocyte ascorbate concentrations
for vitamin C
Urinary excretion of 4-pyridoxic acid
for vitamin B 6
Balance studies Controlled intake and excretion Protein requirements
Animal studies Biochemical measurements Vitamin E and red blood cell hemolysis
Factorial estimation Measure losses + bioavailability Iron requirements
Epidemiologic observational studies Estimate intake and measure losses Iodine intake and excretion
Observed intakes in healthy populations
a. Source: Dietary reference intake reports [6–10].
Functional outcome Vitamin A and night-blindness
Dietary intake data Vitamin K
be at a value less than 10 mg; however, if the criterion
chosen is the amount of vitamin C at which ascorbate
is first excreted in urine when increasing doses are
consumed, assumed to represent a more complete saturation
of body stores and thus a purported mechanism
to handle oxidative stress [6], then the ANR will be at
a much higher value. It is thus possible to have multiple
ANRs, each corresponding to a different indicator or
criterion of adequacy (fig. 1). It is then up to nutrition
and public health policy planners to determine which
level of adequacy is desirable or possibly attainable
in the population group of interest. The choice of the
criterion, assuming it has a strong scientific basis, is a
policy–risk management decision.
Steps in determining the ANR for a specific group
The applicability of the ANR to the population for
which it is developed is improved if the data used meet
certain standards. Some important factors are listed in
box 2. Whatever data are finally selected, it is important
to be transparent by identifying the data used, their
source, and the rationale for their choice.
Nutrient research methods that evaluate human
nutrient needs
A. A. Yates
Methods used to establish nutrient requirements
include those where specific biochemical measures or
functional changes can be specifically attributed to the
level of intake and followed as intake varies.
Factorial estimation. For many nutrients in normal
metabolism, nutrient turnover occurs such that the
amount of the nutrient (or its by-products) excreted
roughly approximates the amount that needs to be