Design, Validation and Reproducibility of a Short Food Frequency Questionnaire to Assess Fruit and Vegetable Intake in Schoolchildren from Northwest Mexico

In Mexico, the 2012 National Health and Nutrition Survey estimated that 65.6% of the schoolchildren aged 5-11 years has inadequate intake of fruits and vegetables. This study was conducted to validate and determine the reproducibility of a short Food Frequency Questionnaire (FFQ) designed to measure changes in fruit and vegetable intake in schoolchildren from Northwest Mexico. To the development of the FFQ, a total of 249 Dietary Recalls (24HR) were collected from 189 schoolchildren. To evaluate validity and reproducibility, two non-consecutive 24HR (as reference method) and two FFQ were collected from 124 schoolchildren. They were randomly divided into two groups: intervention (62) used for reproducibility and control (62) to evaluate validity. The intervention group received a program that promotes consumption of fruits and vegetables for a period of 6 months. Spearman correlations, Wilcoxon test and Bland-Altman plots were used to assess validity. Reproducibility statistics included Spearman correlations, Percent agreement and Weighted Kappa (κw) test and Bland-Altman plot. For validity, the mean intake estimated did not differ significantly for vegetable and the combined vegetable and fruit but it was different in fruit intake. There was a moderate correlation between FFQ1 and the 24HR to estimate the consumption of fruit or vegetable (r = 0.38, r = 0.48) and improves for fruit and vegetables combined (r = 0.69) and the bland and altman plot, showed a homogeneous dispersion of points around the line of the differences for the consumption of fruit and vegetable. For FFQ reproducibility the spearman coefficient values ranged from 0.47 for fruit intake to 0.73 for vegetable and fruit combined intake. Cross-classification between the two methods showed that > 30% of subjects were classified correctly and the κw ranged between 0.425 for fruit to 0.605 for vegetable and fruit, indicating from moderate to substantial level of agreement. The results on validation and reproducibility indicate that the two methods (FFQ and 24HR) give similar results. Food frequency questionnaire has validity and reproducibility to evaluate intake of fruit and vegetable in schoolchildren from northwest Mexico, and can be used to evaluate changes in fruit and vegetable intake on intervention programs, specially aimed to increase the consumption of such food.