Abstract
BackgroundInaccurate self‐report of portion sizes is a major cause of measurement error in dietary assessment. To reduce this error, different portion size estimation aids (PSEAs) have been developed, including food images (image based, IB‐PSE) and textual descriptions of portion sizes (text‐based, TB‐PSE). We assessed the accuracy of portion size estimation by IB‐PSE and TB‐PSE.MethodsTrue intake of one lunch was ascertained in forty participants. Self‐reported portion sizes were assessed after 2 and 24 hours by means of TB‐PSE and IB‐PSE, in random order. Wilcoxon's tests were used to compare mean true intakes to reported intakes. Moreover, proportions of reported portion sizes within 10% and 25% of true intake were assessed. An adapted Bland‐Altman approach was used to assess agreement between true and reported portion sizes. Analyses were conducted for all foods and drinks combined and for predetermined food types.ResultsNo significant differences were observed between reported portion sizes at 2 and 24 hours after lunch. Combining median relative errors of all foods items resulted in an overall 0% error rate for TB‐PSE and 6% error rate for IB‐PSE. Comparing reported portion sizes within 10% (31% vs. 13%) and 25% (50% vs. 35%) of the true intake showed a better performance for TB‐PSE compared to IP‐PSE, respectively. Bland‐Altman plots indicated a higher agreement between reported and true intake for TB‐PSE compared to IB‐PSE.ConclusionsAlthough the use of TB‐PSE still results in measurement error, our results suggest a more accurate dietary intake assessment with TB‐PSE than IB‐PSE.
Highlights
Accurate dietary assessment is essential in nutrition research
The reliability of IB-PSE has mainly been examined by exposing participants to foods and food images simultaneously while focussing on perception and not conceptualization and memory.22-24 the majority of previous research only compared portion size estimation aids (PSEAs) to weighed portion sizes as a reference technique.12,19,21-24 To the best of our knowledge, none of the previous studies examined the accuracy of portion size estimation using a combination of textual descriptions of household measures, standard portion sizes and estimation in grams and IB-PSE
The reported intake and its estimation error for “all foods and drinks combined” using IB-PSE significantly differed from true intake while no statistically significant difference was observed between the reported intake and its estimation error from true intake using TB-PSE
Summary
Accurate dietary assessment is essential in nutrition research. dietary intake is still often assessed using paper-pencil tools, i.e. food frequency questionnaires (FFQs), food records (FRs) and 24-hour recalls (24hRs), dietary assessment techniques have advanced rapidly in recent years. Previous research indicates that IB-PSE is influenced by three main elements, namely perception, conceptualization and memory.[13] Despite these elements of potential error, IB-PSE is suggested to be a useful aid to estimate portion sizes.14,21-24 there is only limited evidence on the reliability of IB-PSE in real-life situations.[14,19] Up to now, the reliability of IB-PSE has mainly been examined by exposing participants to foods and food images simultaneously while focussing on perception and not conceptualization and memory.22-24 the majority of previous research only compared PSEAs to weighed portion sizes as a reference technique.12,19,21-24 To the best of our knowledge, none of the previous studies examined the accuracy of portion size estimation using a combination of textual descriptions of household measures (e.g. spoons, cups, glasses), standard portion sizes (e.g. small, medium, large) and estimation in grams (i.e. for the purpose of this study referred to as text-based portion size estimation or TB-PSE) and IB-PSE. To gain a first insight in the effect of memory on the accuracy of the PSEAs, the portion sizes were reported after either 2 hours or 24 hours
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