A 7-item versus 31-item food frequency questionnaire for measuring fruit, juice, and vegetable intake among a predominantly African-American population.

OBJECTIVE: This study sought to determine which of 2 fruit and vegetable food frequency questionnaires (FFQs) most closely approximated intake measured by the average of four 24-hour dietary recalls.
DESIGN: Participants completed either a 31-item FFQ (n = 70) or 7-item FFQ (n = 76) on 2 occasions approximately 2 weeks apart. During the interval between FFQs1 participants provided four 24-hour dietary recalls via telephone interview. SUBJECTS/
SETTING: Participants were 146 persons with food preparation responsibilities in families of students in grades 3 through 5. Respondents were predominantly African-American women in Atlanta, Ga. STATISTICAL ANALYSIS: Pearson correlation coefficients of log-transformed values estimated the reliability of each FFQ and compared FFQ estimates to reference values. The intraclass correlation coefficient evaluated consistency across 24-hour recalls.
RESULTS: The first FFQs overestimated intake approximately twofold. The 31-item FFQ estimates exceeded 7-item FFQ estimates by approximately 30% . Correlations with recall estimates were high for the 7-item FFQ and moderate to low for the 31-item FFQ. The second FFQ estimates were more highly correlated to reference values. From the first to the second administration, 7-item FFQ estimates dropped from 5.2 to 2.7 servings, and 31-item FFQ estimates dropped from 6.7 to 3.5 servings. Neither FFQ produced highly reliable estimates.
CONCLUSIONS: Mean total fruit and vegetable consumption was closer to reference estimates for the first 7-item FFQ and the second 31-item FFQ. The 7-item FFQ correlated more highly with reference estimates than did the 31-item FFQ. Therefore, we conclude that for African-American adults, a 1-time-administered FFQ using 7 broad food categories correlates more highly with reference values than a FFQ using 31 individual fruit and vegetable items.