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been established for all nutrients, and some nutrients have Adequate Intakes (AIs) rather than EARs. As a result the only nutrients to which the probability approach or the EAR cut-point method (described in Chapter 4) can be applied to assess adequacy in this example are vitamin B 6, vitamin B12, vitamin C, vitamin E, folate, niacin, riboflavin, thiamin, magnesium, phosphorus, and selenium. Additional nutrients will be added as DRIs are developed for them.

To estimate the proportion of the population potentially at risk from excessive intake, the percentage of the group with usual nutrient intake exceeding the Tolerable Upper Intake Level (UL) is determined (see Chapter 6). Again, because ULs have not yet been established for all nutrients, the only nutrients for which the proportion at risk for excessive intake can be estimated are niacin, vitamin B6, folate, choline, vitamin C, vitamin D, vitamin E, calcium, phosphorus, magnesium, fluoride, and selenium. Additional nutrients will also be added to this list as DRIs are developed for them. It should be noted however, that even though EARs or ULs are currently available for some nutrients (e.g., vitamin D, fluoride, and choline), assessment of adequacy or potential risk of excess is not possible because these nutrients are not included in the national intake surveys.

Common Mistakes in Evaluating Dietary Survey Data

Some of the most common mistakes in evaluating dietary survey data arise from inappropriate conclusions drawn from comparing mean nutrient intakes with Recommended Dietary Allowances (RDAs). When mean nutrient intake exceeds the RDA, researchers often conclude—inappropriately —that diets meet or even exceed recommended nutritional standards. At one time, when the RDA was defined as the average intake of a population, this mistake was understandable. However, the current definition of the RDA (and the definition implied in the last two revisions [NRC, 1980, 1989]) specifically defines the RDA as a goal for the individual. In fact, as discussed in Chapter 4, because the variance of usual intake typically exceeds the variance of nutrient requirement for most nutrients, the mean usual nutrient intake of a group must exceed the RDA to have a low prevalence of inadequate intakes. Even if mean usual nutrient intake equals or exceeds the RDA, a significant proportion of the population may have inadequate nutrient intake. This is clearly shown in Table 7-1 and Table 7-2, where both the mean and median of usual intake of folate exceed the RDA, yet approximately 35 per-

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