ABSTRACT
The primary basis o f controversy is the inadequacy of the data base for establishing RDAs ... Controversy also arises because the RDAs are themselves estimates o f nutrient allowances derived from data that are often incomplete and difficult to interpret (italics added). Thus considerable judgment is needed in analyzing these data, estimating the distribution of nutrient requirements in the population, assigning safety margins to account for inter-and intra-individual variability and times of increased need, and extrapolating these data to estimate nutrient allowances for different subgroups in the population, (p. 13)
Lacking an understanding o f the distribution of individual requirements for most nutrients, the RDA committees follow a four-step process in setting requirements. They (a) agree on the basis for determining nutrient status, (b) estimate average requirement and variability in a given population, (c) determine the allowance by
increasing the average requirement enough to meet the needs o f nearly all members o f the population, and (d) for some nutrients, increase the allowance to account for inefficiency of use of the nutrient as consumed (FNB, 1994). Each o f these steps is accompanied by limited information for at least some nutrients, and in those instances, scientific judgment must be substituted. That usually results in the addition of safety factors to ensure that most people are covered.
