Validity and reproducibility of self-reported intake of fruit and vegetable among 6th graders

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Abstract
Objective: Reproducible and valid methods for measuring fruit and vegetable consumption among young school children are urgently needed. The aim of this study was to test the reproducibility and the validity of a newly developed questionnaire on the intake of fruit and vegetable among Norwegian 6th graders. The questionnaire consisted of a 24-h recall part and a food frequency part. Design: A total of 114 pupils completed the questionnaire two times 14 days apart, and another 85 pupils completed the questionnaire and 7-day food diaries. Subjects: Pupils of 6th grade with a mean age of 11.9 y. Results: Spearman correlation coefficients between the frequency part of the questionnaire administered two times varied from 0.62 for fruit to 0.83 for potato, and no difference was seen between the average intakes from the two 24-h recalls. The 24-h recall part of the questionnaire gave higher estimates for the average intake of fruit and juice compared to the 7-day record, while no difference was observed for vegetable intake. Spearman correlation coefficients between the frequency part and the records varied from 0.21 for fruit and potato to 0.32 for the total intake of fruit and vegetable. Conclusions: Both the 24-h recall and the frequency part gave a consistent response on separate occasions over the test–retest study period. The 6th graders were capable of recording yesterday's intake of vegetable, but overestimated the intake of fruit and juice. The ability to rank subjects based on the frequency part was rather low.