Comparison of a dietary record using reported portion size versus standard portion size for assessing nutrient intake

Abstract

Objective: Because the percentage of missing portion sizes was large in the Aerobics Center Longitudinal Study (ACLS), careful consideration of the accuracy of standard portion sizes was necessary. The purpose of the present study was to investigate the consequences of using standard portion sizes instead of reported portion sizes on subjects' nutrient intake. Methods: In 2307 men and 411 women, nutrient intake calculated from a 3-day dietary record using reported portion sizes was compared with nutrient intake calculated from the same record in which standard portion sizes were substituted for reported portion sizes. Results: The standard portion sizes provided signi®cantly lower estimates (> 20%) of energy and nutrient intakes than the reported portion sizes. Spearman correlation coef®cients obtained by the two methods were high, ranging from 0.67 to 0.93. Furthermore, the agreement between both methods was fairly good. Thus, in the ACLS the use of standard portion sizes rather than reported portion sizes did not appear to be suitable to assess the absolute intake at the group level, but appeared to lead to a good ranking of individuals according to nutrient intake. These results were con®rmed by the Continuing Survey of Food Intake by Individuals (CSFII), in which the assessment of the portion size was optimal. When the standard portion sizes were adjusted using the correction factor, the ability of the standard portion sizes to assess the absolute nutrient intake at the group level was considerably improved. Conclusions: This study suggests that the adjusted standard portion sizes may be able to replace missing portion sizes in the ACLS database. Keywords Dietary record Epidemiological methodsFood Nutrient intake Portion sizeIn nutritional epidemiology studies, minimizing measurement error is a key element in the successful elucidation of diet±disease relationships. One of the main errors in the assessment of nutrient intake occurs during the determination of portion size. Where information about portion size is missing, standard portion sizes have traditionally been used. This assumes that standard portion sizes accurately re¯ect the amount typically consumed. However, ®ndings on the accuracy of standard portions are con¯icting 1±8 . As part of the large-scale observational ACLS, dietary intake was assessed using the dietary record method. Information about portion size was obtained by estimating the amount for each food consumed. However, for many food items information on portion size was not available. Since the percentage of missing portion sizes was large (22%), this prompted the need to determine whether standard portion sizes were able to replace missing portion sizes in the ACLS data set.The aim of the present study is to investigate in the ACLS database the consequences of using standard portion sizes instead of reported portion sizes on subjects' nutrient intakes. Furthermore, we evaluated the effect of substituting standard portion sizes for reported portion sizes on nutrient intake in th...

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