María Carmen Cenit

First of all, we would like to express our gratitude for your careful reading of our work and acknowledge the constructive nature of the observations

Background: Dietary habits are crucial for preventing many diseases, particularly in children and adolescents. Accurate assessment of dietary intake is essential for understanding the relationship between diet and health in these age groups. Objective: This study aimed to evaluate the reproducibility and validity of a Spanish version of the European Prospective Investigation into Cancer and Nutrition (EPIC) Food Frequency Questionnaire (FFQ) in 150 Spanish children and adolescents aged 10 to 17 using the average of 9 days of 24-h dietary recall (24H-DR) as a reference. Methods: Intraclass correlation coefficients (ICCs) were calculated to asses reproducibility and Spearman/Pearson correlation coefficients were calculated to assess validity and reproducibility. Results: The average ICCs were 0.41 for crude nutrients, 0.31 for food groups, 0.31 for energy-adjusted nutrients, and 0.4 for energy-adjusted food groups. Spearman/Pearson correlation coefficients averaged 0.39 and 0.41 for crude and energy-adjusted nutrients, respectively, and 0.51 and 0.47 for corresponding food groups. Regarding validity, the average correlation coefficient for crude, energy-adjusted, and de-attenuated nutrients was 0.32, 0.50, and 0.50, respectively. The highest crude coefficient was 0.50 for vitamin C and fiber, while the highest energy-adjusted coefficient was 0.76 for protein and carbohydrates. The highest de-attenuated coefficient was 0.72 for vitamin B6. Conclusions: Overall, these results suggest that the EPIC FFQ is a valid and reliable instrument for assessing dietary intake in Spanish children and adolescents.