FIGURE 14-2 Comparison of 1-day and usual intakes for estimating the proportion of a group consuming intakes below the Estimated Average Requirement (EAR).

trient of interest by individuals in the group. Care must be taken to ensure the quality of the information upon which assessments are made so that they are not underestimates or overestimates of total nutrient intake. Estimates of total nutrient intake, including amounts from supplements, should be obtained. For some of the nutrients discussed in this report, drinking water may also be a significant nutrient source. It is also important to use appropriate food composition tables with accurate nutrient values for the foods as consumed. In the example for zinc, both a database of representative zinc values for all foods that contribute substantially to the intakes of this nutrient and a supplement database with the zinc composition of the specific supplements consumed by the population under study are required.

Overestimates of the prevalence of inadequate intakes could result if the data used are based on intakes that are systematically underreported or if foods rich in zinc are underreported. Such underreporting is common in national surveys (Briefel et al., 1997). Currently, a method for adjusting intakes based on underreporting by individuals is not available and much work is needed to develop an acceptable method. Conversely, underestimates of the prevalence of inadequacy would result if zinc-rich foods were overreported. A more extensive discussion of potential sources of error in self-reported