Validation of the folate food frequency questionnaire with serum and erythrocyte folate and plasma homocysteine.

The aim of the present study was to develop and validate a folate food frequency questionnaire (FFQ)1 designed to measure dietary folate equivalents. The self-administered FFQ containing 39 items and a reference period of 1 month (i.e. the previous month), was validated against three biomarkers: serum and erythrocyte (RBC) folate, and plasma homocysteine (Hcy). Subjects were women (n=99) between the ages of 21 and 87 years. The Pearson correlation coefficients for folate intake and biomarkers were 0.36, 0.34 and -0.25 for serum and RBC folate, and plasma Hcy, respectively. A principal component factor analysis was performed on the three biomarkers to calculate the folate status factor. The Pearson correlation for the folate status factor and folate intake was 0.39. The FFQ described in this study is a valid tool for measuring folate intake expressed as dietary folate equivalents in adult women and is suitable for future investigations about the relationship between folate and disease, or as an educational tool.