Using the Dietary Reference Intakes

This content was archived on June 24, 2013.

This factsheet provides a brief introduction to appropriate uses of the Dietary Reference Intakes (DRIs) for dietary assessment and planning. It does not include sufficient detail needed for the competent application of the DRIs. Nutrition and health professionals should consult the resources listed in the section, Use of the DRIs in Community Nutrition and Dietetic Practice.

Understanding the background, the functional indicators of nutritional adequacy upon which the DRIs are based, the statistical underpinnings for the various uses of the DRI values, and the difference between use with individuals and groups is critical for the appropriate application of the DRIs.

Overview of the Dietary Reference Intakes

The Dietary Reference Intakes (DRIs) are nutrient reference values that replace the 1990 Recommended Nutrient Intakes (RNIs) in Canada and the 1989 Recommended Dietary Allowances in the United States. The DRIs are established using an expanded concept that includes functional indicators of good health and prevention of chronic disease, as well as adverse health effects from excessive nutrient intakes. As was the case with the RNIs, each type of DRI refers to the average daily nutrient intake of healthy individuals over time.

The introduction of the DRIs, especially the Estimated Average Requirement (EAR) and the Tolerable Upper Intake Level (UL), provides better tools for use in dietary assessment and planning for individuals and for groups. The DRIs were developed anticipating a variety of uses such as:

• assessment of diets of individuals and groups;/li>
• design and evaluation of diets in a variety of institutions;
• creation of nutrition guidelines and education programs;
• development of regulations around the nutritional quality of the food supply.

The figure below illustrates relationships among the different types of Dietary Reference Intakes. The table that follows summarizes the DRI definitions and the concepts illustrated by the figure.

FIGURE: Relationship of DRI values to risk of nutrient inadequacy
and risk of adverse health effects

View TABLE: DRI Definitions and Relationship to Risk of Inadequacy and Risk of Adverse Effects

The reports of the Subcommittee on Interpretation and Uses of Dietary Reference Intakes provide useful guidance to nutrition practitioners using the DRIs:

• Applications in Dietary Assessment (2000)
  
• Applications in Dietary Planning (2003)

Each report presents the theoretical and statistical underpinnings for the various uses of the DRI values, presents sample applications, and provides guidelines to help professionals determine when specific uses would be inappropriate.

Appropriate Use of DRIs - Overview

Most applications of the DRIs fall into two broad categories: assessment and planning.

• Dietary assessment involves a comparison of usual nutrient intakes with nutrient requirements, and examines the probability of inadequate or excessive intakes.
• Dietary planning aims to plan usual diets that have an acceptably low probability of nutrient inadequacy or excess.

Clearly, these two general applications are interrelated. In most situations, planning is an ongoing activity in which planners set goals for usual intake, assess whether the goals are achieved and then modify their planning procedures accordingly.

Dietary assessment and dietary planning can be conducted for an individual or for a group. The methods and the appropriate DRI value to use differ in each case.

The following chart provides a summary of the appropriate uses of the DRIs but lacks the detail needed for their correct application. For more details on using the Dietary Reference Intakes, refer to the Food and Nutrition Board reports on Applications in Dietary Assessment (2000) and Applications in Dietary Planning (2003).

It is also important to note that DRIs are standards for apparently healthy people, and not meant to be applied to those with acute or chronic disease or for repletion of previously deficient individuals.

View Table: Summary of Appropriate Uses of Dietary Reference Intakes

Use of the DRIs in Dietary Assessment

For more details on using the Dietary Reference Intakes for dietary assessment, refer to the Food and Nutrition Board report on Applications in Dietary Assessment (2000).

Whether assessing diets of individuals or of groups, two types of information are needed:

1. accurate knowledge of the usual (long-term) intake of the individual or group
   -the number of days needed to accurately assess usual intake differs among nutrients, as well as among individuals or groups
   
2. nutrient requirement(s) of the individual or group
   -requirement is the lowest continuing intake level of a nutrient that, for a specified indicator of adequacy, will maintain a defined level of nutritional adequacy
   

Assessing Individual Diets

Interpreting nutrient intake data in relation to the DRIs can enhance the assessment of an individual's diet; however, the information obtained must be interpreted cautiously as it is only one small component of a nutritional status assessment. Ideally, intake data are combined with clinical, biochemical, and/or anthropometric information to provide a valid assessment of nutritional status. These physiological data can be used to supplement or confirm estimates of inadequacy based on dietary data. For example, a usual intake well below the RDA or AI would be a reason to further assess the individual's nutritional status through laboratory testing or clinical examination. Individuals whose usual intake exceeds the UL may be at risk of adverse health effects.

Assessment of dietary adequacy for an individual is difficult because of the imprecision involved in estimating an individual's usual intake and the lack of knowledge of an individual's requirement. The individual's true usual intake and true requirements must be estimated. Thus, assessment of dietary adequacy for an individual must be interpreted cautiously in combination with other types of information about the individual.

Assessing Group Intakes

Dietary assessment of groups (for example, a population survey) can provide information on the prevalence of nutrient inadequacy and the prevalence of nutrient excess. Researchers may also study diets of smaller groups with common characteristics to determine whether their intakes are adequate or whether there is a proportion of the group at risk for adverse health effects. Assessing the diets of groups can be used to develop food and nutrition policy and can also be useful in determining whether food and nutrition programs are effective. Depending on the results of the assessment, intervention strategies might be developed to address any problem areas.

Dietary assessment at the group level typically involves comparing usual nutrient intakes with nutrient requirements to assess the prevalence of inadequacy among the group. Two approaches have been developed:

• the probability approach, which involves determining the risk of inadequacy to each individual in the group and summing the probabilities (weighted average of the risk of inadequacy)
• the EAR cut-point method, a simplified version of the probability approach that can be used when specific conditions are met, to approximate the proportion of the group with intakes below requirements

The RDA should not be used as a cut-point for assessing nutrient intakes of groups because a serious overestimation of the proportion of the group at risk of inadequacy would result.

For nutrients with an AI, the best that can be done is to look at mean and median intake relative to the AI. When the AI has been set based on the mean intake of a healthy group, similar groups with mean intakes at or above the AI can be assumed to be adequate. When the AI has been experimentally derived or developed from a combination of experimental and intake data, there is less confidence in the assessment. When mean intakes of groups are below the AI, nothing can be inferred about the adequacy of the group's intake.

The UL can be used as a cut-point against which to measure usual intakes in order to estimate the proportion of a group at potential risk of adverse effects from excessive intake of a nutrient.

Dietary Assessment Summary

View Table: Dietary Assessment Summary

Use of the DRIs in Dietary Planning

For more details on using the Dietary Reference Intakes for dietary planning, refer to the Food and Nutrition Board report on Applications in Dietary Planning (2003).

Whether diets are being planned for individuals or for groups, the goal is to plan usual diets that are nutritionally adequate (such that the probability of nutrient inadequacy or excess is acceptably low).

• For individuals, the goal of planning is to achieve usual intakes that are close to the RDA or the AI.
• For groups, the goal is to determine a usual intake distribution that results in a low prevalence of intakes that are inadequate or at risk of being excessive.

When using the DRIs for planning dietary intakes for individuals or for groups, it is helpful to consider the process and functional indicators used for developing the DRIs for specific nutrients. Special considerations for planning include factors that affect nutrient bioavailability, such as the source, chemical form and dietary matrix, as well as the physiological, lifestyle and health factors that may alter nutrient requirements and therefore recommended intakes.

Planning Individual Diets

The goal of planning diets for individuals is to have a low probability of inadequacy while minimizing potential risk of excess for each nutrient. The RDA or AI is used as the target nutrient intake for individuals, and planners should be aware that there is no recognized benefit to usual intakes in excess of these levels. Food-based nutrition education tools, such as Eating Well with Canada's Food Guide, are often used to help an individual plan a healthy diet.

Planning Diets for Groups

The goal of planning for groups is to achieve a distribution of usual nutrient intakes that provides for a low prevalence of inadequate intakes and a low prevalence of intakes that may be at potential risk of adverse effects due to excessive intake. To do this, an acceptable prevalence of inadequacy must be defined and the distribution of usual intakes in the group must be estimated. The target usual intake distribution can then be determined. The procedure used for planning intakes of groups differs depending on whether the group is relatively homogeneous or is composed of a number of subgroups that differ in nutrient and energy requirements. In most situations, planning diets for groups is an ongoing endeavour in which dietary intakes are planned, intakes are assessed to judge the success of the planning activity, and planning efforts are modified accordingly.

View Image: Schematic decision tree for dietary planning

Dietary Planning Summary

View Table: Dietary Planning Summary