Over the past decade, knowledge of nutrient requirements has increased substantially, resulting in a set of new dietary reference standards called the Dietary Reference Intakes (IOM, 1997, 1998, 2000b, 2001, 2002/2005, 2005a). The DRIs replace the earlier Recommended Dietary Allowances and are the appropriate standards to use in determining whether diets are nutritionally adequate without being excessive.
The DRIs for micronutrients include four reference standards—the Estimated Average Requirement, the Recommended Dietary Allowance, the Adequate Intake, and the Tolerable Upper Intake Level (IOM, 2003a)—as follows.
Estimated Average Requirement (EAR) is the usual intake level that is estimated to meet the requirement of half the healthy individuals in a life stage and gender group. At this level of intake, the other half of the healthy individuals in the specified group would not have their needs met.
Recommended Dietary Allowance (RDA) is the usual intake level that is sufficient to meet the nutrient requirement of nearly all healthy individuals in a particular age and gender group (97.5 percent of the individuals in a group). If the distribution of requirements in the group is assumed to be normal, the RDA can be derived as the EAR plus two standard deviations of requirements.
Adequate Intake (AI)—When information is not sufficient to determine an EAR (and, thus, an RDA), then an AI is set for the nutrient. The AI is a recommended average daily nutrient intake level based on experimen-tally derived intake levels or approximations of observed mean nutrient intakes by a group (or groups) of apparently healthy people who are maintaining a defined nutritional state or criterion of adequacy.
Tolerable Upper Intake Level (UL)—Many nutrients have a UL, which is the highest level of usual nutrient intake that is likely to pose no risks of adverse health effects to individuals in the specified life stage group. As intake increases above the UL, the risk of adverse effects increases. The absence of a UL does not imply that the nutrient does not have a tolerable upper intake level, but, rather, that the available evidence at this times does not permit its estimation.
Three of the four DRIs—the EAR, AI, and UL—are appropriate to use in assessing the nutrient intakes of population subgroups. The RDA, however, should not be used in assessing group intakes. Tables F-1A and F-1B in Appendix F—Supplementary Information—present the DRIs for the micronutrients examined in the assessment of the nutrient adequacy of the diets of WIC-eligible population subgroups.