Evaluation of the Validity of a Food Frequency Questionnaire and 24-Hour Dietary Recall to Assess Dietary Iron Intake in Children and Adolescents from the South American Youth/Child Cardiovascular and Environmental Study

Background A food frequency questionnaire (FFQ) for South American children and adolescents was developed, but its validity for assessing dietary iron intake has not been evaluated. Objective To evaluate the validity of the FFQ and 24-hour dietary recalls (24h-DR) for assessing dietary iron intake in children and adolescents. Design The South American Youth/Child Cardiovascular and Environmental study is a multicenter observational study, conducted in five South American cities: Buenos Aires (Argentina), Lima (Peru), Medellin (Colombia), Sao Paulo, and Teresina (Brazil). The FFQ assessed dietary intake over the previous 3 months, and the 24h-DR was completed three times (2 weekdays and 1 weekend day) with a minimum 5-day interval between recalls. Blood samples were collected to assess serum iron, ferritin, and hemoglobin levels. Participants and setting Data of 99 children (aged 3 to 10 years) and 50 adolescents (aged 11 to 17 years) from public and private schools were collected during 2015 to 2017. Main outcome measures Dietary iron intake calculated from the FFQ (using the sum of daily iron intake in all food/food groups) and 24h-DR (mean of 3 days using the multiple source method). Statistical analyses performed Dietary iron intake in relation to blood biomarkers were assessed using Spearman rank correlations adjusted for sex, age, and total energy intake, and the quadratic weighted κ coefficients for agreement. Results Spearman correlations showed very good coefficients (range = 0.78 to 0.85) for the FFQ in both age groups; for the 24h-DR, the coefficients were weak in children and adolescents (range = 0.23 to 0.28). The agreement ranged from 59.9% to 72.9% for the FFQ and from 63.9% to 81.9% for the 24h-DR. Conclusion The South American Youth/Child Cardiovascular and Environmental study FFQ exhibited good validity to rank total dietary iron intake in children and adolescents, and as well as the 24h-DR, presented good strength of agreements when compared with serum iron and ferritin levels.