and gender group. At this level of intake, the remaining 50 percent of the specified group would not meet their nutrient needs. For some life stage or gender groups, data had to be extrapolated to estimate this value. In deriving the EARs, contemporary concepts of the reduction of disease risk were among the factors considered, rather than basing reference values solely upon the prevention of nutrient deficiencies.
The EAR is expressed as a daily value averaged over time, for most nutrients at least one week. Because the EAR is a dietary intake value, it includes an adjustment for an assumed bioavailability of the nutrient. The EAR is used in setting the RDA, and it may be used as one factor for assessing the adequacy of intake of groups and for planning adequate intakes by groups.
The Recommended Dietary Allowance (RDA) is the average daily dietary intake level that is sufficient to meet the nutrient requirements of nearly all (97 to 98 percent) individuals in a life stage and gender group. The RDA applies to individuals, not to groups. The EAR serves as the foundation for setting the RDA. If the standard deviation (SD) of the EAR is available and the requirement for the nutrient is normally distributed, the RDA is set at 2 SDs above the EAR:
RDA = EAR + 2 SDEAR.
If data about variability in requirements are insufficient to calculate a standard deviation, a coefficient of variation (CVEAR) of 10 percent is assumed in this report, and the resulting equation for the RDA is
RDA = EAR + 2 (EAR × 0.1)
RDA = EAR (1.2).
If the estimated CV is 15 percent, the formula would be
RDA = EAR (1.3).