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FIGURE 13-2 Effect of multiple days of observation on the apparent distribution of nutrient intake. The mean is the same for both, but the percentage of individuals with intakes less than the Estimated Average Requirement (EAR) is overestimated by the 1-day observations. Adapted from NRC (1986); originally from Hegsted (1972).

discrepancy between the EAR and intake represents a true concern. In contrast, Figure 13-4 reveals that nearly all adults have intakes of vitamin B12 that exceed the EAR. This graph does not provide any perspective on the problem of vitamin B12 absorption by many elderly, however, because the EAR assumes that adequate absorption of food-bound vitamin B12 occurs.

Overestimates of the prevalence of inadequate intakes could result from the underreporting of food intake; underestimates of the prevalence of inadequate intake are also possible. (See Chapter 2 for a discussion of many of the potential sources of error in self-reported dietary data.)

As suggested above, several questions need to be considered when assessing the intake of populations:

  • What kinds of adjustments can be made, if any, for biases in the food intake data?

  • What factors should be considered in interpreting the findings in different populations?

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