A comparison of fruit and vegetable intake estimates from three survey question sets to estimates from 24-hour dietary recall interviews.

BACKGROUND: Fruit and vegetable (F/V) intake surveillance can provide information critical to the design and evaluation of interventions and the assessment of progress toward national intake objectives. The CDC's Youth Risk Behavior Surveillance System (YRBSS) assesses F/V intake among high school students using six questions about the frequency of intake in times per day. It is not known whether F/V intake frequency in times per day can be used as a proxy for intake in servings per day.
OBJECTIVE: To compare F/V intake estimates based on responses to three sets of survey questions, including the standard set of six YRBSS questions, with criterion F/V intake in servings per day based on data from 24-hour dietary recall interviews. PARTICIPANTS/
SETTING: Study participants were 610 high school students who completed an in-class questionnaire and three telephone-administered 24-hour dietary recall interviews. The questionnaire asked students how many times they consumed 100% fruit juice and ate fruit, carrots, potatoes, green salad, and other vegetables during the "past 7 days" (set 1), the number of times they did so "yesterday" (set 2), and the number of cup-equivalents of fruits and vegetables they consumed per day (set 3). MAIN OUTCOME MEASURE: Mean estimated F/V intake either as "times/day" or "servings/day" and the percentage of students whose estimated F/V intake was ≥1, ≥2, and ≥3 times/day or servings/day. STATISTICAL ANALYSES PERFORMED: t tests and corrected Pearson correlations were used to compare F/V intake estimates based on survey question responses with estimates based on responses to the 24-hour dietary recall interviews.
RESULTS: Mean F/V intake estimates (in times/day or servings/day) based on responses to all sets of survey questions were significantly more than servings/day estimates based on responses to the 24-hour dietary recall interviews, and the percentages of students meeting each intake cutpoint were also more. Of the three sets of survey questions, the standard YRBSS questions produced estimates and percentages that were most consistently closest to 24-hour dietary recall interview estimates.
CONCLUSIONS: For brief self-administered questionnaires of high school students, the current YRBSS questions are recommended for monitoring F/V intake even though mean intake estimates in times/day will likely be higher than, and are not a proxy for, mean intake estimates in servings/day.