Validity and reproducibility of a food frequency questionnaire to estimate folate intake in a Mexican population

To evaluate the reproducibility and validity of folate intake (FI) estimated from a food frequency questionnaire (FFQ), taking into account the retention factor (RF) associated with meal preparation processes. A total of 497 healthy adult participants were interviewed with a FFQ. A second interview was performed one year later of a sample of 100 randomly selected individuals who had not modified their diet during the previous year. In addition,serum folate (SF) concentrations were measured by radioimmunoassay to evaluate the validity of FI. Reproducibility of IF was 0.36 and 0.34 for folate without FR and with FR, respectively. SF concentration significantly correlated with FI (0.18 with RF; 0.21 without RF, p