Relative validity of a semi-quantitative food frequency questionnaire to estimate dietary intake according to the NOVA classification in Mexican children and adolescents.

Abstract: Background Ultra-processed foods (UPF) are associated with poor diet quality and chronic diseases. UPF falls into one of the four groups classified according to the extent and purpose of processing: Group 1 includes unprocessed and minimally processed foods (MPF); group 2 refers to processed culinary ingredients (PCI); group 3, processed foods (PF); and group 4, UPF. Objective The aim of this study was to evaluate the relative validity of a semi-quantitative food frequency questionnaire (SFFQ) compared to two 24-hour dietary recalls to estimate dietary intake per NOVA food group in Mexican children and adolescents. Design This study is a secondary analysis of dietary data from a subsample of children and adolescents who participated in the 2012 Mexican National Health and Nutrition Survey Participants/setting The study participants were 217 children (5 to 11 years) and 165 adolescents (12 to 19 years) with complete information for the SFFQ and two 24 hour-dietary recalls (24DRs). Main outcome measures Daily averages of energy intake and % of energy intake for each NOVA category were calculated using the SFFQ and two 24DRs. Statistical analysis To assess relative validity, the SFFQ was compared with two 24DRs to estimate dietary intake per NOVA food group. Mean differences, Spearman correlations and intra-class correlations coefficients (ICC) and Bland–Altman plots for continuous variables and weighted kappa for ordinal variables were calculated. Results For percentage of energy intake, ICC in children and adolescents were moderate for MPF (ICC=0.47, ICC=0.56, respectively) and UPF (ICC=0.53, ICC=0.57, respectively). Bland–Altman plots indicated reasonably consistent agreement for UPF and MPF groups in children and adolescents. Classification by quintiles was acceptable in all groups. Conclusions Data from this study indicated reasonable relative validity of the SFFQ to rank the percentage of energy intake from MPF and UPF in Mexican children and adolescents.