puter program, they may show between-interviewer differences in responses (Kohlmeier et al., 1997).
Household inventories are weak measures of total food intake because of food waste, food consumed by guests or pets, and the large amount of food consumed outside of the home. They also require assumptions about the distribution of food consumption among the people within a household when the household includes more than one person.
Maintaining weighed food records over multiple days can provide a solid basis for nutrient assessment as long as the recording of food intake does not influence usual intake behavior and as long as seasonality in nutrient intake, where it exists, is adequately captured.
In summary, intakes assessed by 24-hour recall, diet records, or quantitative diet histories remain the strongest bases for quantitative assessment of nutrient adequacy using the Dietary Reference Intakes (DRIs). Quantitative assessments require both accurate determination of the quantities of foods consumed by an individual and inclusion of all of the foods that contribute even modestly (more than 5 percent) to the total nutrient intake. Not all dietary intake instruments are designed to meet these requirements. Their use for this purpose is likely to result in inaccurate assessments.
Either because of poor memory or a reluctance to report foods felt to be inappropriate, people often omit, add, or substitute foods when recalling or reporting dietary data. On average, total energy intake tends to be underreported by about 20 percent, although the degree of underreporting varies with weight status, body mass index, etc. (Johnson et al., 1998; Lichtman et al., 1992; Mertz et al., 1991). The most common additional food items that were remembered after prompting in the U.S. Department of Agriculture's Continuing Survey of Food Intake by Individuals (1994–1996, Day 1) were beverages, including alcoholic beverages, and snack food, with 5 to 10 percent of nutrient totals being added after prompting (B. Perloff, U.S. Department of Agriculture, unpublished observations, 1998). If foods —and therefore nutrients—are underreported, then the prevalence of inadequate intakes for a population or the probability of inadequacy for an individual may be overestimated. Little is