The Recommended Dietary Allowances (RDAs) are not useful in estimating the prevalence of inadequate intakes for groups. As described above, the EAR should be used for this purpose.
In this report, Adequate Intakes (AIs) are assigned only for infants and reflect the average intake of the nutrient from human milk. Human milk and, in the case of nutrients reviewed in this report, infant formulas with the same nutrient composition as human milk (after adjustment for bioavailability) provide the appropriate levels of nutrients for infants of presumably healthy well-nourished mothers. Groups of infants consuming formulas with lower levels of nutrients than human milk may be at some risk of inadequacy, but the prevalence of inadequacy cannot be quantified.
The proportion of the population with usual intakes below the Tolerable Upper Intake Level (UL) is likely to be at no risk of adverse effects due to overconsumption, while the proportion above the UL may be at some risk. In the case of vitamin C, the UL is 2,000 mg/day for adults; the NHANES III data in Figure 9-2 and Figure 9-3, which include reported intake from supplements, illustrate that the U.S. adult population did not exceed this UL at the time of the survey.
In typical food-based diets, ULs for vitamin C, vitamin E, and selenium can rarely be exceeded. Supplement use would be the primary way to exceed these ULs.
The mean intake of a population cannot be used to evaluate the prevalence of intakes above the UL. A distribution of usual intakes, including intakes from supplements, is required in order to assess the proportion of the population that may be at risk of overconsumption.