An historical review of the Harvard and the National Cancer Institute food frequency questionnaires: Their similarities, differences, and their limitations in assessment of food intake

Food Frequency Questionnaires (FFQ) are pre-coded forms consisting of selected foods that are usually grouped based on their nutrient constitution. By carefully selecting food items that are most important to the basic diet and by grouping them, a relatively short questionnaire can be developed to estimate nutritional exposure accurately, at a relatively low cost. Two major FFQs, the Harvard University/Willett's Questionnaire and the National Cancer Institute/Block's Questionnaire as well as their modified versions have been used in different studies. In general the contents of two FFQs are similar. However, nuances in structure and cognitive aspects set them apart. The objectives of this paper are three fold. First, to provide a historical review of the process of design and development of each FFQ. Second, to compare their cognitive and structural similarities and differences, and finally, to discuss their limitations and biases associated with estimating food intake.