Validation of the folate food frequency questionnaire in vegetarians.

Adequate folate status has an important role in the prevention of chronic and developmental diseases and is considered a potential public health issue. Therefore, valid tools for measuring the vitamin intake are needed. In our previous study a folate food frequency questionnaire (FFQ) designed to measure dietary folate equivalents was developed and validated among adult women against serum and erythrocyte (red blood cell) folate and plasma homocysteine. The aim of the present study was to validate the FFQ in vegetarians (n=75). The Pearson correlation for folate intake and biomarkers was 0.41, 0.36 and -0.15 for serum and red blood cell folate and plasma homocysteine, respectively. The quadratic weighted kappa value for biomarkers was above 0.2 and the gross misclassification of subjects into quartiles was less than 10%. The FFQ is a valid tool for measuring dietary folate equivalent intake in Croatian vegetarians.