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5 Food-Based Assessment of Dietary Intake
Pages 57-84

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From page 57...
... To the extent possible, the committee focused on studies conducted with populations served by WIC: women in the childbearing years, children younger than 5 years of age, and low-income women and children from diverse ethnic backgrounds. The term food-based dietary assessment methods refers to assessment tools used to estimate the usual nutrient or food intake of an individual or a group.
From page 58...
... commonly used research-quality dietary assessment methods, including their strengths and limitations, (3) methods that compare food intakes with the Dietary Guidelines, and (4)
From page 59...
... Therefore, the accurate approximation of an individual's usual intake requires data collection over many days (Basiotis et al., 1987, Beaton, 1994, IOM, 2000a, Sempos et al., 1993~. Identifying Who Falls Above or Below a Cut-Off Point Estimating the proportion of a population group with a nutrient intake above or below L requires the collection of one day of intake data per person in the population plus an independent second day of intake for at least a subsample of the population (Carriquiry, 1999, IOM, 2000a, Nusser et al., 1996~.
From page 60...
... The high ratios2 reflect large day-to-day within-person variation in the consumption of different foods. In summary, a large body of literature indicates that day-to-day variation in nutrient and food intake is so large in the United States that one or two diet recalls or food records cannot provide accurate information on usual nutrient and food intake for an individual.
From page 61...
... As discussed in the previous section, recalls and records are not good measures of an individual's usual intake unless a number of independent days are observed.4 On average, diet recalls and food records tend to underestimate usual intake energy intake in particular. On the other hand, FFQs and diet histories tend to overestimate mean energy intakes, depending on the length of the food lists that are used and subjects' abilities to estimate accurately the frequency and typical portion sizes of foods they consume.
From page 62...
... to recall all foods and beverages consumed yesterday (for a 24-hr period such as midnight to midnight) ; food descriptions and amounts for each food are recalled; amounts are estimated using portion size measurement aids pattern of usual intakes in the past than other methods; generally designed to assess total diet Tends to overestimate nutrient intakes compared with diet recall and food record Provides information on the frequency and types of foods typically eaten, preparations, and detailed descriptions of foods Quantification of intake imprecise due to poor recall or use of standard portion sizes Reflects a single day's intake rather than usual intake (not a valid estimate of an individual's usual intake)
From page 63...
... ; may or may not ask about portion sizes for a specified period of time, Usually self-administered typically recorded as consecu tive 3, 7, or 14 d, but can also be nonconsecutive daily re cords over a period of time One-day records kept intermit tently over a year may reflect an individual's usual intake Multiple records may be required to estimate usual nutrient intake Provides quantitative estimates of foods and nutrients Tends to underestimate energy intake Foods eaten away from home are less accurately described than those eaten at home Useful to assess qualitative intake and dietary patterns Designed to estimate usual intake of foods; semiquantitative methods are used to estimate nutrients from food frequency information; useful for estimating foods that are consumed frequently, infrequently, or never Difficult to estimate intake of individual food items when foods are grouped Provides little information on food preparation methods or specific details about foods Tends to overestimate energy and some nutrients (extremely high nutrient estimates are not uncommon) Nutrient estimates often require adjustment for caloric intake continued
From page 64...
... influenced by current diet individual's intake reduces Higher energy intakes in first reliability of a single day's vs. subsequent administra- or few days' intake lions in children ages 5-18 yr Repeated diet history shown to be reproducible based on 1-mo diet history and 24-h urinary nitrogen excretion
From page 65...
... , or 0.5-0.8 after statistical adjustment for energy and within-person variation Eating habits are not affected by method Potential for systematic bias food items Potential for systematic bias Multiple days provide reliable information for less frequently consumed foods Intraclass coefficients range from 0.5 to 0.9 for two 7-d food records Many types of FFQ instruments available Reliability is influenced by heterogeneity of population Less standardized method, especially for infants and young children May require subject to group foods Requires subject to estimate frequencies of intake Correlation coefficients of 0.4-0.7 for food groups and food items Food lists may not contain cultural foods usually eaten Many FFQs have been calibrated (rather than validated) against other methods; some FFQs have been tested against biomarkers Higher energy intakes in first vs.
From page 66...
... 66 DIETARYRISKASSESSMENTIN THE WIC PROGRAM TABLE 5-1 Continued Criterion or Characteristic Diet History 24-Hour Diet Recall Issues relevant Requires a knowledgeable Difficult to estimate total intake to WIC proxy respondent to de- among breast-fed infants populations scribe infants' and pro- Infants' and preschoolers' in schoolers' diets takes may require multiple Since infants' and young chit- proxy respondents to com dren's diets can be variable pletely capture all foods from day-to-day, it may be eaten at home, day care, pre difficult for a proxy re- school, and other places spondent to accurately es- throughout the day timate intake over a certain Overweight adolescent and period of time adult females tend to under report total energy intake Standardized methodology facilitates capturing ethnic foods and food preparation methods Respondent High respondent burden Low respondent burden burden Takes much more time than Requires less effort on the part other methods to administer of the subject Respondents must be highly High response rates cooperative Does not require literacy if administered by trained in terviewer Resource re- High Medium/high depending upon quirements Requires highly trained inter- whether recall is computer viewers assisted and computer-coded Procedure can be administered by telephone Administration 1 h or more time 20-30 min. on average
From page 67...
... Food list may not contain the foods consumed by cultural or ethnic groups and be an incomplete list for the individual Commonly used FFQs have been developed more for the general population and major subgroups, and may not be appropriate for all cultural dietary patterns Extreme reporting by the individual (characterized as very high or very low energy intakes) may render the instrument useless for about 20% of individuals Overestimates energy intake by 50% in children ages 4-6 yr High respondent burden Requires much effort and accuracy by subject Subject must be literate; poorer response rates compared with diet recall and FFQ Medium/high Procedure can be automated Requires more editing and processing time compared with diet recall Depends on number of days recorded and subject's abilities Low to medium respondent burden, depending on length and whether self-administered High response rates Low Does not require highly trained interviewers May be self-administered May be scored with automated procedures or optically scanned 10-15 min.
From page 68...
... (n = 95 n = 102 whites; half 1-2 with three diet recalls) yr and half 3-5 yr English-speaking Dietary method 84-item Harvard Service FFQ and subset with a second FFQ completed twice FFQ and three 24-h recalls by parents compared to three 24-h telephone recalls over the same 4 wk using the Nutrition Data System Major findings Correlation coefficients Adjusted correlation coefficients ranged from 0.26 to exceeded 0.5 except for vitamin 0.63 for nutrients (av- A; women who greatly overes erage 0.52)
From page 69...
... compared with three 24-h telephone recalls (for past 2-5 wk) in children ages 1-4.9 years Correlations with diet recalls and comparison by quartile differed by racial/ethnic group; most correlations were lower than 0.5; results were generally higher for Block than for Harvard Service FFQ; neither FFQ was judged satisfactory for Hispanics or for children African Americans and whites completed the FFQ in less than 10 min.
From page 70...
... Even if usual nutrient intake could be assessed with several days of observations of an individual's intake, collection of multiple days of intake is not feasible in the WIC clinic setting (see criterion 6, "Operational Constraints," in Chapter 4~. There are two approaches to minimizing within-person variability in dietary data.
From page 71...
... With this method, the individual is expected to summarize the usual intake of food items, based on her knowledge of how her dietary choices vary from day to day. In this case, reliability is typically judged by assessing the reproducibility of the intake estimates from repeated administrations of the questionnaire, and validity is assessed by comparing the intake estimates with usual nutrient intakes estimated from multiple days of intake using either diet recalls or diet records.
From page 72...
... A review of dietary assessment among preschool children found that diet recalls both overestimated and underestimated energy intake (Serdula et al., 2001~. A review of dietary method studies among children ages 5-18 years also found that food records underestimated energy intake compared to doubly labeled water (McPherson et al., 2000~.
From page 73...
... That is, people who truly do not meet criteria based on the Dietary Guidelines or nutrient cut-off points would be misclassified as ineligible for WIC. Portion Size Estimation Diet recalls and food records are subject to respondents' errors in reporting or recalling portion sizes consumed.
From page 74...
... Mean correlation coefficients cluster around 0.5 (Jain and McLaughlin, 2000, Jain et al., 1996, Longenecker et al., 1993~. In general, correlations for adolescents between the validation standard and diet method were higher for single diet recalls and diet records than for FFQs (McPherson et al., 2000~.
From page 75...
... In general, these correlation coefficients are not better than those found by investigators studying nutrients rather than foods. Correlations with Usual Intake from Diet Recalls or Food Records Young Children Few validity studies have been conducted of questionnaires designed to assess the diets of young children (Baranowski et al., 1991, Blum et al., 1999, Goran et al., 1998, McPherson et al., 2000, Persson and Carlgren, 1984~.
From page 76...
... with three 24-hour diet recalls conducted by telephone among 94 children and 235 women participating in WIC (see Table 52~. Most correlations between the FFQ and the average of three recalls were below 0.5.
From page 77...
... If a lower, more realistic value representing the percentage of the population that meets the Dietary Guidelines were used, the percent of eligible persons who would be found ineligible would be larger (Table 5-5~. Limitations and Uses of Brief Dietary Methods Shortening and simplifying FFQs may make it easier for WIC clientele to respond (whether the FFQ is self-administered or administered by WIC personnel)
From page 78...
... They suggested that the screener would be useful in combination with other dietary methods that also estimate energy intake. Others have found that measures taken to shorten and simplify questionnaires reduce their validity in the research setting.
From page 79...
... The committee found no studies that directly examine the performance of dietary intake tools used to compare an individual's food intake with the Dietary Guidelines, but did find the following related information. Dietary Intake Form Method Strohmeyer and colleagues (1984)
From page 80...
... the ability to identify the nutritionally adequate diets was no better than chance. Either MAR method would depend on data from one or two 24-hour diet recalls, and thus would be subject to all the limitations of diet recalls presented earlier in this chapter.
From page 81...
... For example, 1 cup of some kinds of breakfast cereal may be about half grain and half sugar by weight so should be counted as only one-half serving from the breads and cereals food group. To determine the numbers of servings of foods in the five major food groups from diet recalls or records accurately, researchers at the U.S.
From page 82...
... covering diet as a whole and measuring "how well the diets of all Americans conform to the recommendations of the Dietary Guidelines and the Food Guide Pyramid" (Variyam et al., 1998~. Theoretically, an HEI score would be a comprehensive indicator of whether a potential WIC participant of at least 2 years of age fails to meet Dietary Guidelines.
From page 83...
... Similarly, research-quality FFQs result in substantial misclassification of individuals in a group when results from FFQs are compared with those from sets of diet recalls or food records. Moreover, studies by Bowman et al.
From page 84...
... 84 DIETARYRISKASSESSMENTIN THE WIC PROGRAM ficiently valid and practical to distinguish individuals who are ineligible from those eligible for WIC based on the criterionfailure to meet Dietary Guidelines or based on cut-off points for nutrient intake. Nonetheless, dietary tools have an important role in WIC in planning or targeting nutrition education for WIC clients, as described in Chapter 9.


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