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particularly when intakes are compared with the Tolerable Upper Intake Level (UL) for nutrients such as niacin. For some nutrients, it may also be necessary to change the units of measurement (e.g., dietary folate equivalents [DFEs], as suggested for folate [IOM, 1998b] and the milligrams of α-tocopherol, suggested for vitamin E in place of α-tocopherol equivalents [IOM, 2000]).

RESEARCH TO IMPROVE STATISTICAL METHODS FOR USING THE DRIs TO ASSESS INTAKES OF INDIVIDUALS

Chapter 3 and Appendix B present an approach to assess the adequacy of an individual's usual intake of nutrients with an Estimated Average Requirement (EAR) or with an Adequate Intake (AI). The following two serious limitations in the application of the method were identified:

  • Currently there is not sufficient information to permit calculation of the standard deviation (SD) of daily intake for each individual. It is well known that the SD of daily intake is typically heterogeneous across individuals; however, no research has been conducted to allow the adjustment of a pooled SD estimate to better reflect an individual's daily variability in intakes.

  • The approach for testing whether usual intake is greater than requirements (or greater than the AI or less than the Tolerable Upper Intake Level [UL]) makes the critical assumption that daily intakes for an individual are normally distributed. No alternative methodology exists for the many instances in which this assumption is untenable. Research is needed to devise methods for quantitatively assessing individual intakes when the distribution of daily intakes is not symmetrical around the individual's usual intake.

RESEARCH TO IMPROVE STATISTICAL METHODS FOR USING THE DRIs TO ASSESS INTAKES OF GROUPS

The assessment of dietary intake data for groups is challenging because these analyses (presented earlier in this report) do not lend themselves to standard statistical methods. Several methodological issues deserve attention from the scientific community.

Methods for developing standard deviations for prevalence estimates (sometimes referred to as the standard error of the estimate) should be investigated. As discussed in Chapter 8, estimates of the prevalence of inadequacy are not precise because of the uncertainty existing both in requirement estimates and in intake assessments.



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