Assessment of the food list and serving size of a Food Frequency Questionnaire in an adult population

This study examined both the food list and portion size values from a Food Frequency Questionnaire (FFQ) among participants in a case-control study in S?o Paulo, Brazil. Two hundred adult respondents to a case-control study were randomly selected (101 men and 99 women; age range: 35-69 years). FFQ food items were examined on the basis of their contribution to total population nutrient intake estimated by 24-hour dietary recall (1-DR). We examined the frequency distribution of equivalent-gram weights of each selected food from the 1-DR and identified the portion sizes as small, medium, and large in the distribution (percentiles 25, 50, and 75, respectively). The FFQ provided close estimation of total fat, saturated fatty acids, cholesterol, total fiber, vitamin B6, and folic acid compared to the 1-DR (paired t-test; p < 0.05). The FFQ food list covered the study population's main dietary nutrient sources.