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Suggested Citation:"What Are Dietary Reference Intakes?." Institute of Medicine. 1998. Dietary Reference Intakes: A Risk Assessment Model for Establishing Upper Intake Levels for Nutrients. Washington, DC: The National Academies Press. doi: 10.17226/6432.
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BOX 1 Uses of Dietary Reference Intakes for Healthy Individuals and Groups

Type of Use

For the Individual

For a Group

Planning

RDA: aim for this intake.

EAR. Use in conjunction with a measure of variability of the group's intake to set goals for the mean intake of a specific population

 

AI; aim for this intake.

 

 

UL: Use as a guide to limit intake;chronic intake of higher amounts may increase risk of adverse effects.

 

Assessmenta

EAR: use to examine the possibility of inadequacy: evaluation of true status requires clinical, biochemical, and/oranthropometric data.

EAR: use in the assessment of the prevalence of inadequate intakes within a group.

 

UL: use to examine the possibility of overconsumption; evaluation of true status requires clinical, biochemical, and/or anthropometric data.

 

RDA = Recommended Dietary Allowance

EAR = Estimated Average Requirement

AI = Adequate Intake

UL = Tolerate Upper Intake Level

a Requires statistically valid approximation of usual intake.

components not traditionally classified as ''nutrients," but purported to play a beneficial role in human diets. It is expected that when evaluation of all groups of nutrients and food components are completed as part of this ongoing process, the model for risk assessment of nutrients will have been fully developed and validated.

What are Dietary Reference Intakes?

Dietary Reference Intakes (DRIs) are reference values that are quantitative estimates of nutrient intakes to be used for planning and assessing diets for healthy people. They include both recommended intakes and ULs as reference values (see Box 1). Although the reference values are based on data, the data are often scanty or drawn from studies that had limitations in addressing the question. Thus, scientific judgment is required in setting the reference values:

Suggested Citation:"What Are Dietary Reference Intakes?." Institute of Medicine. 1998. Dietary Reference Intakes: A Risk Assessment Model for Establishing Upper Intake Levels for Nutrients. Washington, DC: The National Academies Press. doi: 10.17226/6432.
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  • Recommended Dietary Allowance (RDA): the average daily dietary intake level that is sufficient to meet the nutrient requirement of nearly all (97 to 98 percent) healthy individuals in a group.
  • Adequate Intake (AI): a value based on observed or experimentally determined approximations of nutrient intake by a group (or groups) of healthy people—used when an RDA cannot be determined.
  • Tolerable Upper Intake Level (UL): the highest level of daily nutrient intake that is likely to pose no risk of adverse health effects to almost all individuals in the general population. As intake increases above the UL, the risk of adverse effects increases.
  • Estimated Average Requirement (EAR): a nutrient intake value that is estimated to meet the requirement of half the healthy individuals in a group.

The development of DRIs expands on the periodic reports called Recommended Dietary Allowances, which have been published since 1941 by the National Academy of Sciences. It is expected that as additional groups of nutrients and food components are reviewed over the next few years, the process and initial models developed will evolve and be further refined. As new information or processes develop, reference intakes will be periodically reassessed in keeping with this evolving process.

Recommended Dietary Allowance

The Recommended Dietary Allowance (RDA) is the average daily dietary intake level that is sufficient to meet the nutrient requirement of nearly all (97 to 98 percent) healthy individuals in a particular gender and life stage group (life stage considers age and, when applicable, pregnancy or lactation).

Process for Setting the RDA

The process for setting the RDA depends on being able to set an Estimated Average Requirement (EAR). That is, the RDA is derived from the nutrient requirement so if an EAR cannot be set, no RDA will be set. The EAR is the daily intake value of a nutrient that is estimated to meet the nutrient requirement of half the healthy individuals in a life stage and gender group. Before setting the EAR, a specific criterion of adequacy is selected, based on a careful review of the literature. When selecting the criterion, reduction of disease risk is considered along with many other health parameters. The RDA is set at the EAR plus twice the standard deviation (SD) if known (RDA = EAR + 2 SD); if data about variability in requirements are insufficient to calculate an SD, a coefficient of variation for the EAR of 10 percent is ordinarily assumed (RDA = 1.2 x EAR).

Suggested Citation:"What Are Dietary Reference Intakes?." Institute of Medicine. 1998. Dietary Reference Intakes: A Risk Assessment Model for Establishing Upper Intake Levels for Nutrients. Washington, DC: The National Academies Press. doi: 10.17226/6432.
×

The RDA for a nutrient is a value to be used as a goal for dietary intake by healthy individuals. The RDA is not intended to be used to assess the diets of either individuals or groups or to plan diets for groups.

Adequate Intake

The Adequate Intake (AI) is set instead of an RDA if sufficient scientific evidence is not available to calculate an EAR. The AI is based on observed or experimentally determined estimates of nutrient intake by a group (or groups) of healthy people. For example, the AI for young infants, for whom human milk is the recommended sole source of food for the first 4 to 6 months, is based on the daily mean nutrient intake supplied by human milk for healthy, full-term infants who are exclusively breastfed. The main intended use of the AI is as a goal for the nutrient intake of individuals. Other uses of AIs will be considered by another expert group.

Tolerable Upper Intake Level

The Tolerable Upper Intake Level (UL) is the highest level of daily nutrient intake that is likely to pose no risk of adverse health effects to almost all individuals in the general population. As intake increases above the UL, the risk of adverse effects increases. The term tolerable intake was chosen to avoid implying a possible beneficial effect. Instead, the term is intended to connote a level of intake that can, with high probability, be tolerated biologically. The UL is not intended to be a recommended level of intake. There is no established benefit for healthy individuals if they consume nutrient intakes above the RDA or AI.

ULs are useful because of the increased interest in and availability of fortified foods and the increased use of dietary supplements. ULs are based on 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 only, the UL is based on nutrient intake from those sources only, not on total intake. The UL applies to chronic daily use.

For many nutrients, there are insufficient data on which to develop a UL. This does not mean that there is no potential for adverse effects resulting from high intake. When data about adverse effects are extremely limited, extra caution may be warranted.

Suggested Citation:"What Are Dietary Reference Intakes?." Institute of Medicine. 1998. Dietary Reference Intakes: A Risk Assessment Model for Establishing Upper Intake Levels for Nutrients. Washington, DC: The National Academies Press. doi: 10.17226/6432.
×
Page 2
Suggested Citation:"What Are Dietary Reference Intakes?." Institute of Medicine. 1998. Dietary Reference Intakes: A Risk Assessment Model for Establishing Upper Intake Levels for Nutrients. Washington, DC: The National Academies Press. doi: 10.17226/6432.
×
Page 3
Suggested Citation:"What Are Dietary Reference Intakes?." Institute of Medicine. 1998. Dietary Reference Intakes: A Risk Assessment Model for Establishing Upper Intake Levels for Nutrients. Washington, DC: The National Academies Press. doi: 10.17226/6432.
×
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The model for risk assessment of nutrients used to develop tolerable upper intake levels (ULs) is one of the key elements of the developing framework for Dietary Reference Intakes (DRIs). DRIs are dietary reference values for the intake of nutrients and food components by Americans and Canadians. The U.S. National Academy of Sciences recently released two reports in the series (IOM, 1997, 1998). The overall project is a comprehensive effort undertaken by the Standing Committee on the Scientific Evaluation of Dietary Reference Intakes (DRI Committee) of the Food and Nutrition Board (FNB), Institute of Medicine, National Academy of Sciences in the United States, with active involvement of Health Canada. The DRI project is the result of significant discussion from 1991 to 1996 by the FNB regarding how to approach the growing concern that one set of quantitative estimates of recommended intakes, the Recommended Dietary Allowances (RDAs), was scientifically inappropriate to be used as the basis for many of the uses to which it had come to be applied.

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