The Office of Dietary Supplements requested the Tufts Medical
Center Evidence-based Practice Center (EPC) to conduct an exercise
to identify the issues and challenges of including evidence-based
methods as a component of the process used to develop nutrient
reference values (such as the Dietary Reference Intakes DRI])
issued by the Institute of Medicine (IOM). This work was performed
under a task order issued by the Agency for Healthcare Research and
Quality EPC program. The Tufts EPC assembled a group of nutrition
experts from academic institutions and relevant federal government
agencies, led participants in teleconferences and meetings,
conducted exercises in formulating questions that would be amenable
to systematic reviews of the scientific literature, and identified
the challenges and limitations of applying this method to processes
previously used to establish nutrient reference values. This report
summarizes the impetus behind this project, approach taken, and the
lessons learned. Nutrient reference values have significant public
health and policy implications. This type of dietary guidance is
needed for planning diets, assessing the adequacy of diets in
individuals and populations, developing nutrition education and
guidance, and for setting reference values for nutrition labeling.
The IOM Food and Nutrition Board has issued reports on the DRIs for
a wide range of nutrients. Six reports have been published and are
organized around groups of nutrients. Contents of the reports
include a summary of what is known about the nutrient function in
the human body, selection of indicators of adequacy of nutrient
intakes or nutrient levels, factors that may affect how the
nutrients are utilized and that affect requirements, and how
nutrients may be related to the prevention of chronic disease
across age groups. Various study committees were convened to
evaluate a body of available scientific evidence for specific
nutrients. Primarily human studies were reviewed and selected
animal studies were used when human data are absent or conflicting.
Available evidence was weighted according to quality, peer review
status, biological plausibility, and whether similar estimates
would be derived from different indicators. However, the process of
establishing DRIs has been variable and has evolved as experience
accrued from study committees. Concern has been expressed that in
some cases the methods used to determine DRIs have suffered from a
lack of transparency and consistency. Moreover, differences in the
reference values derived by various groups of nutrition experts
worldwide have been noted for the same nutrient when all presumably
have used the same body of available evidence. Given the importance
of defining reliable nutrient reference values, there is a need for
an explicit, objective, and transparent process to set these
values. Evaluating evidence is a major component of informing the
process. Because new studies are constantly being published, it
would also be desirable to have a framework that allows efficient
updating when new information becomes available. Although the
mandate to different committees around the world has previously
been different, with the globalization of the food supply and
health risks it should be expected that evaluating similar evidence
will result in similar recommendations. Over the past 15 years, the
concept of evidence-based medicine building upon the foundation of
systematic reviews, meta-analyses and related methods as important
tools for evidence-based practice, has gained widespread acceptance
in the evaluation of medical evidence for healthcare
decision-making. The application of this approach to evaluating the
nutrition literature could provide for the transparent,
comprehensive and objective evaluation of scientific evidence and
could provide support for a framework for a consistent approach to
establishing nutrient reference values for all dietary components.
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