Abstract
Background
The assessment of food intake is challenging and prone to errors; it is therefore important to consider the reliability and validity of the assessment methods.
Objective
The aim of this study was to analyze the reproducibility and validity of a developed food-frequency questionnaire (FFQ) for use among adolescents.
Design
In total, 58 students (aged 13–14) from four different schools in the southern part of Norway participated in the reproducibility study of filling out the FFQ 4 weeks apart. In addition, 93 students participated in the relative validity study where the FFQ was compared to 2×24-hour dietary recalls, while 92 students participated in the absolute validity study where the intakes of fatty acids and vitamin D from the FFQ were compared to fatty acids and 25-hydroxy-vitamin D3 in whole blood.
Results
The median Spearman correlation coefficient for all nutrients in the test–retest reliability study was 0.57. The median Spearman correlation for all nutrients in the relative validity study was 0.26, while the correlations coefficients were low in the absolute validity study with n-3 fatty acid coefficients ranging from 0.05 to 0.25, and absent for vitamin D (r=0.000).
Conclusion
The test–retest reproducibility was considered good, the relative validity was considered poor to good, and the absolute validity was considered poor. However, the results are comparable to other studies among adolescents.
Acknowledgements
This work was supported by grants from the Norwegian Institute of Public Health and the University of Agder. The content of this article reflects only the author's view and the Norwegian Institute of Public Health is not liable for any use that may be made of the information contained therein.
Conflict of interest and funding
The authors declare no conflict of interest and funding.
