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## Dietary Reference Intakes: Applications in Dietary Assessment (2000) Institute of Medicine (IOM)

### Citation Manager

. "7 Specific Applications: Assessing Nutrient Intakes of Groups Using the Dietary Reference Intakes." Dietary Reference Intakes: Applications in Dietary Assessment. Washington, DC: The National Academies Press, 2000.

 Page 138

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DRI DIETARY REFERENCE INTAKES: Applications in Dietary Assessment

the centering age value, while all individuals in the other group have ages that are either much lower or much higher than the centering value, then the adjustment above will lead to biased inferences about the effect of FSP participation on the prevalence of inadequacy.

• Only one covariate has been included in this example. The approach above extends naturally to the case of more than one covariate, and the same centering principle would hold. If, for example, income was a second covariate and if the range of incomes in the sample went from \$10,000 to \$40,000, then the appropriate centering value for income would be the midpoint (\$40,000 − \$10,000)/2 + \$10,000 = \$25,000. In this case, one would be adjusting observed intakes to look like the intakes that would have been observed if all individuals had been 35 years of age and earned \$25,000.

• The adjustment above relies on the ability to accurately specify a regression model for intake. The model needs to contain all covariates thought to be associated with intake, particularly if they are also thought to be correlated with FSP participation. The estimated regression coefficients will have better statistical properties when intakes are approximately normally distributed.

The hypothetical example below (see also Table 7-3) illustrates the first four steps of this approach to assess whether FSP participation affects the mean intake of the group or the prevalence of inadequacy of nutrient A. In this example, it is suspected that age may influence intake of nutrient A and may also be associated with FSP participation. For each of a large group of individuals, 2 days of intake data are available, and the age of each individual is known. Some are FSP participants (FSP = 1) and others are not (FSP = 0). The overall group mean intake of nutrient A is 772 units. Table 7-3 shows data for six of these individuals.

Step 1. In the first step, a regression model is fitted to the intake data (column 4 of the table). The resulting prediction equation is:

Observed intake = −9 + 21.7 × age + 68.7 × FSP

Step 2. Next, standard predicted intakes are calculated for each individual for each day of intake. The regression coefficient associated with age generated from the intake data is used, but the coefficient for FSP participation and the intercept are not included. The

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 Front Matter (R1-R14) Contents (R15-R18) Summary (1-18) I. Historical Perspective and Background (19-20) 1 Introduction and Background (21-28) 2 Current Uses of Dietary Reference Standards (29-42) II. Application of DRIs for Individual Diet Assessment (43-44) 3 Using Dietary Reference Intakes for Nutrient Assessment of Individuals (45-70) III. Application of DRIs for Group Diet Assessment (71-72) 4 Using the Estimated Average Requirement for Nutrient Assessment of Groups (73-105) 5 Using the Adequate Intake for Nutrient Assessment of Groups (106-112) 6 Using the Tolerable Upper Intake Level for Nutrient Assessment of Groups (113-126) 7 Specific Applications: Assessing Nutrient Intakes of Groups Using the Dietary Reference Intakes (127-144) IV. Fine-Tuning Dietary Assessment Using the DRIs (145-146) 8 Minimizing Potential Errors in Assessing Group and Individual Intakes (147-161) 9 Research Recommended to Improve the Uses of Dietary Reference Intakes (162-167) 10 References (168-178) Appendix A: Origin and Framework of the Development of Dietary Reference Intakes (179-184) Appendix B: Nutrient Assessment of Individuals: Statistical Foundations (185-202) Appendix C: Assessing Prevalence of Inadequate Intakes for Groups: Statistical Foundations (203-210) Appendix D: Assessing the Performance of the EAR Cut-Point Method for Estimating Prevalence (211-231) Appendix E: Units of Observation: Assessing Nutrient Adequacy Using Household and Population Data (232-238) Appendix F: Rationale for Setting Adequate Intakes (239-253) Appendix G: Glossary and Abbreviations (254-261) Appendix H: Biographical Sketches of Subcommittee Members (262-266) Index (267-281) Summary Table: Estimated Average Requirements (282-283) Summary Table: Tolerable Upper Intake Levels (284-286) Summary Table: Recommended Intakes for Individuals (287-289)