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mated dietary intakes in apparently healthy population groups, or on a review of data from different approaches that considered alone do not permit a reasonably confident estimate of an EAR.

Similarities Between the AI and the RDA

Both the AI and RDA are to be used as a goal for individual intake and thus both represent recommended levels of intake for individuals. In general, the values are intended to cover the needs of nearly all persons in a life stage group. (For infants, the AI is the mean intake when infants in the age group are consuming human milk. Larger infants may have greater needs, which they meet by consuming more milk.) As with RDAs, AIs for children and adolescents may be extrapolated from adult values if no other usable data are available.

Differences Between the AI and the RDA

There is much less certainty about the AI value than about the RDA value. Because AIs depend on a greater degree of judgment than is applied in estimating the EAR and subsequently the RDA, the AI may deviate significantly from and be numerically higher than the RDA. For this reason, AIs must be used with greater care than is the case for RDAs (see IOM, 2003). Also, the RDA is usually calculated from the EAR by using a formula that takes into account the expected variation in the requirement for the nutrient, which is not the case for some AIs (see previous section, “Estimated Average Requirement”).

For some nutrients and food components, data are not sufficient for developing either an AI or an RDA for apparently healthy individuals. This is the case for sulfate (Chapter 7), as its requirement appears to be met by consumption of the sulfur-containing amino acids methionine and cysteine, and adequate data are lacking to determine the extent to which inclusion of sulfate in the diet can decrease the requirements for these indispensable amino acids.

Tolerable Upper Intake Level

The Tolerable Upper Intake Level (UL) is the highest level of daily nutrient intake that is likely to pose no risk of adverse health effects for almost all apparently healthy individuals in the specified life stage group (see Figure 1-1). As intake increases above the UL, the potential risk of adverse effects may increase. The term tolerable in-

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