Design Characteristics of Food Frequency Questionnaires in Relation to Their Validity

The authors investigated the role of food frequency questionnaire (FFQ) design, including length, use of portion-size questions, and FFQ origin, in ranking subjects according to their nutrient intake. They also studied the ability of the FFQ to detect differences in energy intake between subgroups and to assess energy and protein intake. In a meta-analysis of 40 validation studies, FFQs with longer food lists (200 items) were better than shorter...