The Food Frequency Questionnaire (FFQ) has become the dominant method for assessing dietary intakes in epidemiological studies, especially to evaluate the relationship of diet with the occurrence of non-transmissible chronic diseases. The FFQ is a tool designed to evaluate the usual diet of a population and has the advantages of being easy and quick to apply and efficient in the epidemiological practice of identifying usual food consumption, in addition to its low cost. Compared to other tools, it replaces the measurement of one or several days of food intake with overall information on the intake over a more extended period of time. It becomes a useful tool in studies, when its use is preceded by carefully planned methodological procedures, to ensure the reliability and accuracy of the data. For such purpose, validation studies are required to estimate measuring errors related to the method. If these errors are not known, the true effect of a diet-disease relationship may be jeopardized. This article is a systematic approach to methodological considerations for FFQ validation studies.
Food Frequency Questionnaire; Validation study; Usual Intake