Validation of 2 Brief Fruit and Vegetable Assessment Instruments Among Third-Grade Students

Relative validity and reproducibility of a semi-quantitative food frequency questionnaire to assess fruit and vegetable consumption in school-aged children

Background

Since the beneficial effects of fruit and vegetable (FV) consumption on health are well known due to the synergy of their nutrients and non-nutrients, it is crucial to have good tools to assess the FV intake. A food frequency questionnaire (FFQ) is an adequate method to estimate FV consumption, but it is necessary to relate this dietary method to the geographic and cultural environment. Therefore, this study presented the development of a semi-quantitative FFQ to estimate the FV intake in school-aged children who usually consume cooked homemade and school meals. It also aimed to evaluate the relative validity and reproducibility of the FFQ.

Methods

School-aged children (baseline age 8 years) from 14 primary schools in the city of Zagreb participated in the study during the 2019/2020 school year. Parents/caregivers, together with the children, completed the FFQs and 3-day dietary records (3DDRs). The FFQ was designed to assess the consumption of eight food categories. The FFQ was validated using the 3DDR of 141 children (51.4% of boys), whereas the reproducibility test included the FFQ of 161 children (53.4% of boys).

Results

Of the eight food categories, FFQ overestimates the consumption of three and underestimates the consumption of three food categories (p < 0.05; Wilcoxon signed rank test) compared to the 3DDR. De-attenuated correlation coefficients estimated a significant relationship (0.217–0.384) between the FFQ and 3DDR. Cross-classification analysis revealed that overall, 28–41% of children were classified in the same quartile, whereas less than 10% of children were extremely misclassified for all food categories obtained from 3DDR and FFQ1. κw values showed fair agreement for all food categories. The Bland–Altman analysis results showed a relatively small bias for all food categories (median between -11.7 and -54.8 g), with no systematic patterns between the FFQ and 3DDR. No differences were found between food categories estimated with the FFQs on both occasions, and Spearman’s correlation coefficients ranged from 0.664 to 0.712 (p < 0.01). Cronbach’s alpha values (α > 0.700) indicate good internal consistency, and ICCs (range 0.724–0.826; p < 0.01) indicate good reproducibility of the FFQ.

Conclusion

The results indicate reasonable relative validity and acceptable reproducibility of the FFQ for estimating FV consumption among school-aged children.

Using pre- and post-survey instruments in interventions: determining the random response benchmark and its implications for measuring effectiveness

OBJECTIVE

The present communication demonstrates that even if individuals are answering a pre/post survey at random, the percentage of individuals showing improvement from the pre- to the post-survey can be surprisingly high. Some simple formulas and tables are presented that will allow analysts to quickly determine the expected percentage of individuals showing improvement if participants just answered the survey at random. This benchmark percentage, in turn, defines the appropriate null hypothesis for testing if the actual percentage observed is greater than the expected random answering percentage.

DESIGN

The analysis is demonstrated by testing if actual improvement in a component of the US Department of Agriculture's (USDA) Expanded Food and Nutrition Education Program is significantly different from random answering improvement.

SETTING

USA.

SUBJECTS

From 2011 to 2014, 364320 adults completed a standardized pre- and post-survey administered by the USDA.

RESULTS

For each year, the statement that the actual number of improvements is less than the expected number if the questions were just answered at random cannot be rejected. This does not mean that the pre-/post-test survey instrument is flawed, only that the data are being inappropriately evaluated.

CONCLUSIONS

Knowing the percentage of individuals showing improvement on a pre/post survey instrument when questions are randomly answered is an important benchmark number to determine in order to draw valid inferences about nutrition interventions. The results presented here should help analysts in determining this benchmark number for some common survey structures and avoid drawing faulty inferences about the effectiveness of an intervention.

Test-Retest Reliability and Convergent Validity of Two Brief Fruit and Vegetable Intake Questionnaires among School-Aged Children

Reliable, valid, and easy-to-implement tools are required to assess children's fruit and vegetable intake as part of behavior change-focused nutrition education programs; however, the availability of such instruments is limited. The purpose of this study was to examine the reproducibility and accuracy of two brief fruit and vegetable intake questionnaires among 8- to 12-year-old children. A total of 109 participants from diverse racial/ethnic groups were recruited from urban afterschool programs. The results of two short questionnaires (food web and plate activity) were reproducible between two repeated measures conducted one week apart. Compared to a reference 24-h dietary recall, the food web questionnaire had acceptable convergent validity for assessing children's fruit intake (kappa: 0.51; r = 0.53, p < 0.001), but limited validity for assessing children's vegetable intake (kappa: 0.43; r = 0.33, p < 0.003). Children tended to overestimate intake when visualizing fruit and vegetable consumption via the plate activity questionnaire, indicating that this questionnaire was not a valid tool to assess children's fruit and vegetable consumption at dinner meals. Children's report of fruit intake via the food web questionnaire may be a useful indicator of program success in improving fruit intake.

Using Skin Carotenoids to Assess Dietary Changes in Students After 1 Academic Year of Participating in the Shaping Healthy Choices Program

OBJECTIVE

To determine whether fourth-grade students participating in the Shaping Healthy Choices Program (SHCP), a school-based nutrition intervention, would change vegetable and carotenoid intake measured by skin carotenoids and dietary intake.

METHODS

Single-group pretest-posttest with a self-selected, convenience sample of students (n = 30) participating in the SHCP, which lasted 1 academic year (9 months). Dietary intake of vegetables and carotenoids as measured by Block food frequency questionnaire and skin carotenoids as measured by Raman spectroscopy were collected at the school preintervention and postintervention.

RESULTS

Reported carotenoid intake decreased by 1.5 mg (P = .05) and skin carotenoids decreased by 2,247.9 RRS intensity units (P = .04). Change in reported intake correlated with change in skin carotenoids (r = .43; P = .02).

CONCLUSIONS AND IMPLICATIONS

The reported decrease in vegetable and carotenoid intake was unanticipated; nevertheless, the RRS measurements confirmed this. RRS data can help evaluate changes in fruit and vegetable intake.

Validity of short food questionnaire items to measure intake in children and adolescents: a systematic review

BACKGROUND

Short food questions are appealing to measure dietary intakes.

METHODS

A review of studies published between 2004 and 2016 was undertaken and these were included in the present study if they reported on a question or short item questionnaire (≤50 items, data presented as ≤30 food groups) measuring food intake or food-related habits, in children (aged 6 months to 18 years), and reported question validity or reliability. Thirty studies met the inclusion criteria.

RESULTS

Most questions assessed foods or food groups (n = 29), with the most commonly assessed being fruit (n = 22) or vegetable intake (n = 23), dairy foods and discretionary foods (n = 20 studies each). Four studies assessed food habits, with the most common being breakfast and meal frequency (n = 4 studies). Twenty studies assessed reliability, and 25 studies determined accuracy and were most commonly compared against food records. Evaluation of question performance relied on statistical tests such as correlation.

CONCLUSIONS

The present study has identified valid and reliable questions for the range of key food groups of interest to public health nutrition. Questions were more likely to be reliable than accurate, and relatively few questions were both reliable and accurate. Gaps in repeatable and valid short food questions have been identified that will provide direction for future tool development.