Measuring Food Use in School-aged Children El iza bet h Ra nda I I

utrition programs address the special needs of N school-aged children in areas such as optimizing growth, preventing deficiencies, developing acceptance of foods, preventing dental caries, maximizing intel- lectual performance, and enhancing fitness. Recently, concern has focuvd on developing healthful dietary practices to reduce risks for subsequent development of chronic diseases. Goals are expressed in terms of lifelong compliance with dietary guidelines, * rather than the short-term aim of consuming targeted nutrients in amounts specified in the U.S. Recommended Dietary Allowances (RDAs).

This shift in programmatic goals has ramifications for assessing diets since any one measure is unlikely to be appropriate in all situations. The various methods available differ in the importance given to each of five components: food items consumed, portion sizes, nutri- ent composition, relevant time frame to achieve repre- sentativeness of diet, and evaluative criteria. Ideal measures possess the qualities of validity, reliability, interpretability, and feasibility (cost, personnel needs, respondent burden).’ These attributes are context- specific.

F O O D USE MEASURES When dietary record or recall is used, subjects pro-

vide detailed descriptions of all foods consumed in a specified time period and include estimations of the por- tion size of each food. Diet history involves an interview in which subjects describe foods commonly consumed, including methods of preparation and frequency of use. The food frequency technique uses a concise list of foods selected for their contributions to intakes of the nutrients of interest. Each respondent recalls how fre- quently each food is consumed, and sometimes reports usual portion size.

Dietary Records and Recalls Diet recalls and records provide quantitative assess-

ments of nutrient intake expressed as continuous vari- ables (See “Taking a Bite Out of Eating Behavior: Food Records and Food Recalls of Children,” J Sch Health. 1991; 61(5):198-200, for a detailed report of procedures). They generate separate values for each nutrient of interest, which can be cumbersome when the goal of measurement is to assess overall dietary adequacy. Several investigators have summarized intake by calculating the mean adequacy ratio (MAR). Intakes of each nutrient are expressed as proportions of their respective RDAs (truncated at 1 .O) and averaged over all nutrients of c ~ n c e r n . ~ Precision in diet records and recalls is acquired at the cost of more personnel for interviewing and data management and of higher

Elizabeth Randall, PhD, RD, Assistant Professor, Nutrition Program, State University of New York at Buffalo, 301 Parker Hall, Buffalo, NY 14214.

respondent burden for multiple days of reporting that may result in lower cooperation and data quality. When the quantity or detail of data obtained exceed the demands of a specific measurement need, the costs become exorbitant and simpler measures are pursued.

Measures of Patterns in Food Use Dietary assessment may emphasize food use, for

which specific evaluative criteria are less clearly defined, rather than nutrient intake. Fueled by the attributes of simplicity, feasibility of administration, and ability to estimate intake over the extended period of time appro- priate for programs aiming to develop lifelong behavior, a renewed interest in measures of patterns in food use has emerged.4 Thus, valuable data for describing food use of children and for targeting changes can be ob- tained.

Diet history and the briefer food frequency method both estimate usual dietary intake. The number of times each item in a finite set of foods typically is consumed in a specific time period, such as a week, month, or year, is multipled by the nutrient values assigned to those foods and the products are summed over all foods in the set. These methods do not provide precise estimates of abso- lute nutrient intake, but classify subjects on the basis of their positions relative to others yielding ordinal data. For example, individuals can be assigned quantile ranks based on their positions within a population’s dis- tribution of estimated nutrient intake; they also could be classified based on whether they are consumers of such food types as dairy products and whole grains or for compliance with such dietary guidelines as the inclusion of variety in vegetable use.

Measures of dietary patterns control for within- person variability in daily intake by asking subjects to recall habitual food use. Diet records and recalls esti- mate habitual consumption by replicating estimates on multiple days, the number of days needed determined by the ratio of within:between person variability in daily intake for specific nutrients and the level of accuracy desired. The required number of replicate days can be prohibitive and is larger in children than in adults.6 One week of intakes may satisfy needs for estimating intakes of macronutrients. Micronutrients such as vitamin A and cholesterol may require as many as 21 days to obtain stable intake estimates for a group and a great many more days to accurately estimate the intake of an individual.

Numerous studies have validated briefer, less costly techniques. The commonly used evaluative criterion has been mean values from repeated diet r eco rd~ .~~* Unfortunately, few validation trials have been con- ducted with children.

RELIABILITY A N D VALIDITY ISSUES Diet History

Diet history, originally conceived by B ~ r k e , ~ was in- tended for use in growth and development studies of

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children and requires estimates of food use for individ- ual children over prolonged periods of time. The history method requires subjects to report all foods consumed regularly as well as their frequencies of consumption, portion sizes, and preparation methods.Io A skilled inter- viewer with a sound knowledge of dietetics elicits data that are sufficiently complete and accurate, yet succinct, to assign nutrient values to foods. This feature results in high costs for data collection. Consequently, its use in contemporary, large-scale investigations has been limited.

The reliability and validity of the diet history has been documented.11-13 Test-retest producibility of the data is satisfactory, with correlation coefficients for nutrients ranging from of 0.70 to 0.84. Among women followed annually for four years,13 mean nutrient intakes for the group showed little change, suggesting the technique estimates long-term food intake. Differ- ences in intake of most nutrients (generally 2% to 10% of mean values) were attributed to the two interviewers, reinforcing the need for highly trained personnel. Vali- dation of this method against biochemical markers of nutritional status have been limited. According to Willett,lO determinants of physiological levels, other than diet, of many nutrients are sufficiently numerous that validity of a dietary measure is established by a positive association with the relevant biochemical para- meter. Such relationships have been documented for in- takes of vitamins A and E measured by food frequency.

Adoption of diet history for use with school-aged children is more common in Europe than in North America.14J5 Using both a 24-hour recall and a diet history, Finnish children ages 5-1 3 were interviewed with a parent present.l4 The procedures were repeated seven months later. As would be expected with a mea- sure of habitual food use, test-retest correspondence was greater for the history (0.41 to 0.60) for the various nutrients than for 24-hour recall (-.02 to 0.43).

This study supported Burke’s earlier observation that the history method overestimated intake. Mean intakes calculated from the history method consistently were higher, differing from values based on 24-hour recall data by 30% to 50% depending on the nutrient examin- ed. A Swedish study of children age 1315 interviewed without a parent present further substantiated over- estimation of nutrient intake based on data from a diet history and a 24-hour recall. Mean values differed by 23% to 56% depending on the specific nutrient. Because of overestimation, the history method is commonly used to categorize individuals by level of nutrient intake. Fewer instances of classifying the same child into opposite tertiles occurred with repeated measures of the history technique than with 24-hour reca11.I5

The diet history describes dietary patterns and can accurately classify individuals by quantiles of usual nutrient intake. Its reliance on trained dietary profes- sionals results in prohibitive costs, and efforts have focused on developing a shorter questionnaire in which subjects report frequency of ingestion of an abbrevi- ated, pre-established list of foods selected for their importance as food sources of specific nutrients.16 Food Frequency

With a food frequency instrument, subjects com-

monly report whether a food usually is consumed on a daily, weekly, or monthly basis, and how often it is eaten within that time frame. Nutrient intake estima- tions improve when frequency of food use is supple- mented with portion size data, even when estimated only semi-quantitatively, indicating if the typical por- tion of food is “small” or “large” relative to a specified “average” portion.16 An alternative approach asks sub- jects to alter reported frequency of use to take into account portions deviating from a stated size.l0 For example, subjects who usually consume 12 ounces of a beverage with a portion size specified as eight ounces would increase the reported frequency by 50%. This approach would be inappropriate with subjects lacking the necessary arithmetical skills.

The food frequency method is widely used in epi- demiologic research. Its validity and reliability with adults have been investigated extensivelyI0J6 including consistency, assessments of differences between mean nutrient intake values using data collected with various dietary methods, extent of misclassification of subjects with food frequency data compared to various reference methods, and correlations between nutrient intakes computed from food frequency data and biochemical or physiological indicators of nutritional status. l o This method provides reasonably accurate data capable of classifying individuals by their habitual nutrient intake levels and is feasible for use in assessing the impact of long-term dietary intake.

Treiber et all7 compared 24-hour recall to food fre- quency with preschoolers for whom data were provided by parents. Estimated mean intakes were approximately 30% to 70% higher for all nutrients when measured by food frequency, except for sodium which had a lower estimated intake with this measure. Measures repeated one week later yielded more stable estimates of intakes of specific nutrients with food frequency (0.42 to 0.74) than with 24-hour dietary recall (-0.06 to 0.48). Treiber et a1 concluded food frequency is a good measure of nutrient intake that has the important attribute of detecting dietary change with smaller sample sizes. They cautioned, however, that this method may provide a more generic description of diet that could be less sensi- tive than 24-hour recall to subtle dietary change. Food as it appears on a food frequency list actually may be a composite of related foods such as tomatoes which can be consumed fresh, canned, in mixed dishes, or as a sauce. Changes within such composite foods would not be detected. Findings of Treiber et all7 were based on extensive interviews requiring twice as much time as 24-hour recall to complete. Their findings need corro- boration using a food frequency technique that captures the attribute of brevity.

Food frequency overestimated consumption of staples and underestimated sweets compared to seven- day food records in a Swedish study for children ages four and eight for whom parents provided data.15 Chil- dren, especially at younger ages, may not be reliable chroniclers of their own food intake and surrogates may need to provide the data. Sametin and others” docu- mented that surrogates can supply frequency of food use data of adequate quality for the elderly or deceased subjects, and Treiber et al” confirmed parental ability

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to supply accurate dietary data for preschoolers. Al- though food habits of children resemble those of their parents, children may be even more similar to sibling~,’~ suggesting an additional source of corroborative data for future validation studies.

ADAPTING FOOD FREQUENCY FOR CHILDREN

School-aged children represent a unique population for dietary measurement as well as other measures of health status.20 Food frequency is an inherently simple, widely accepted measure used with populations differ- ing in age, gender geographical location, and social class. Nonetheless, it needs to be adapted when used with subjects such as young children, who differ from normal, healthy adults. Five issues need special atten- tion when constructing a food frequency for use with children:20*21

The Food List. Children are more likely to interpret questions literally, impairing their ability to include all items within composite foods when they fail to recog- nize that commonly consumed items are included in the group.

Time Intervals. A young child’s amorphous concept of the past, being “before now,” makes estimating fre- quency of food use during a specific interval more prob- lematic. Time periods may need to be fixed by meaning- ful start and end points, and this time interval may need to be abbreviated for children who typically have more changeable food patterns.

Response Set. Children tend to acquiesce to adults and to respond affirmatively to authoritatively phrased questions. Children are likely to adopt a response set when they are unsure of the question, do not have an opinion, or are disinterested.

Context of Questioning. Words need to be used that are consistent with a child’s definition of a given situa- tion. Effective probes may need to be more specific since young children may not respond to subtle hints.

Structuring the Questionnaire. Interviews should begin with easy questions on topics of interest, with dif- ficult or threatening questions asked last. Active parti- cipation, such as a card sort approach, may facilitate data collection.

Instrument development work by Baranowski et alZZ and by Simons-Morton et als offers direction for the future. School-aged children successfully recorded fre- quency of food use data daily. Age-appropriate forms were developed that supported collection of data capable of describing dietary intakes in terms of food use targeted in a nutrition intervention to reduce risk of cardiovascular disease. These techniques also could be adapted for use with other dietary guidelines. More

methodological research of this nature is needed to accurately assess the dietary status of young children. H

References 1. The Surgeon General’s Report on Nutrition and Health. Wash-

ington, DC: US Dept of Health and Human Services; 1988:l-81. Publication no (PHS) 88-50210.

2. Vermeersch J. Method for addessing the nutritional status of children. In: The National Evaluation of School Nutrition Programs: Review of Research, vol 1 . Santa Monica, Calif: System Development Corp; 1981;113-225.

3. Krebs-Smith SM, Clark LD. Validation of a nutrient adequacy score for use with women and children. J Am Diet Assoc. 1989;89:

4 . Randall E, Marshall JR, Graham S, Brasure J. Patterns in food use and their associations with nutrient intakes. Am J Clin Nutr.

5 . Simons-Morton BG, Baranowski T, Parcel GS, O’Hara NM, Matteson RC. Children’s frequency of consumption of foods high in fat and sodium. A m J Prev Med. 1990;6(4):218-227.

6. Nelson M, Black AE, Morris JA, Cole TJ. Between- and within- subject variation in nutrient intake from infancy to old age: Esti- mating the number of days required to rank dietary intakes with desired precision. Am J Clin Nutr. 1989;50: 155-167.

7. Medlin C, Skinner JD. Individual dietary intake methodology: A 50-year review of progress. J Am Diet Assoc. 1988;88:1250-1257.

8. Lee-Han H, McGuire V, Boyde NF. A review of the methods used by studies of dietary measurement. J Clin Epidemiol. 1989;42:269-279.

9. Burke BS. The dietary history as a tool of research. J Am Diet

10. Willett W. Nutritional Epidemiology. New York, NY: Oxford University Press; 1990:69-142.

1 1 . Jain M. Diet history: Questionnaire and interview techniques used in some retrospective studies of cancer. J Am Diet Assoc.

12. Staveren WA van, De Boer JO, Burema J. Validity and reproducibility of a dietary history method estimating the usual food intake during one month. A m J Clin Nutr. 1985;42:554-559.

13. Van Beresteyn ECH, Van ’t Hoff MA, Van Der Heiden- Winkeldermaat HJ, Ten Have-Witjes A, Neeter R. Evaluation of the usefullness of the cross-check dietary history method in longitudinal studies. J Chron Dis. 1987;40:1051-1058.

14. Rasanen L. Nutrition survey of Finnish rural children VI. Methodological study comparing the 24-hour recall and the dietary history interview. Am J Clin Nutr. 1979;32:2560-2567.

15. Persson LA, Carlgren G, Measuring children’s diets: Evaluation of dietary assessment techniques in infancy and children. Int J Epidemiol. 1984;13(4):506-517.

16. Block G, Hartman AM. Issues in reproducibility and validity of dietary studies. Am J Clin Nutr. 1989;50:1133-1138.

17. Treiber FA, Leonard SB, Frank G, Musante L, et al. Dietary assessment instruments for preschool children: Reliability of parental response to the 24-hour recall and food frequency questionnaire. J Am Diet Assoc. 1990;90:814-820.

18. Samet JM. Surrogate measures of dietary intake. Am J Clin Nutr. 1989;50: 1139-1 144.

19. Pliner P, Pelchat ML. Similarities in food preferences between children and their siblings and parents. Appetite. 1986;7:333-342.

20. Fink R. Issues and problems in measuring childrens health status in community health research. Soc Sci Med. 1989;29:715-719.

21. Holaday B, Turner-Henson A. Response effects in surveys with school-age children. Nurs Res. 1989;38(4):248-250.

22. Baranowski T, Dworkin R, Henske JC, Clearman DR. Dunn JK, Nader PR, et al. The accuracy of children’s self-reports of diet: Family Health Project. J A m Diet Assoc. 1986;86:1381-1385.

775-783.

1990;52:729-745.

ASSOC. 1947;23 : 1041-1046.

1989;89:1647-1652.

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