FIGURE 1-1 Dietary reference intakes. This figure shows that the Estimated Average Requirement (EAR) is the intake at which the risk of inadequacy is 0.5 (50%) to an individual. The Recommended Dietary Allowance (RDA) is the intake at which the risk of inadequacy is very small—only 0.02 to 0.03 (2 to 3%). The Adequate Intake (AI) does not bear a consistent relationship to the EAR or the RDA because it is set without being able to estimate the average requirement. It is assumed that the AI is at or above the RDA if one could be calculated. At intakes between the RDA and the Tolerable Upper Intake Level (UL), the risks of inadequacy and of excess are both close to 0. At intakes above the UL, the risk of adverse effect may increase.

a coefficient of variation (CV; SD divided by the mean × 100) of 10 percent, which is equal to 1 SD, such that

RDA = 1.2 × EAR.

If the distribution of the nutrient requirements is known to be skewed for a population, other approaches will be used to find the ninety-seventh to ninety-eighth percentile.

The assumed CV of 10 percent is based on extensive data on the variation in basal metabolic rate (FAO/WHO/UNA, 1985; Garby and Lammert, 1984), which accounts for about two-thirds of the daily energy needs of many individuals residing in Canada and the United States (Elia, 1992), and on the similar CV of 12.5 percent estimated for protein requirements in adults (FAO/WHO/UNA, 1985). The assumption is made that the CV of requirements is similar