The Food Frequency Questionnaire (FFQ) is country-specific and was developed for all of the international EPIC centres. It was based on the FFQ used in the Nurses’ Health Study and was designed to measure a participant’s usual food intake during the previous year. The country-specific FFQs were calibrated using a 24hDR recall, which were computer-assisted face-to-face interviews on a subset of the participants using EPICsoft.
Visit the FFQ download and data entry page to download a copy of the FFQ or for information on the data entry.
The questionnaire is a 10-page A4 document, consisting of two parts:
This is the main part of the questionnaire and contains a list of 130 commonly and less commonly consumed foods. For each item on the list, participants are asked to indicate their usual frequency of consumption choosing from nine frequency categories. The categories range from “never or less than once/month” to “6+ times per day”. The servings are specified in terms of units or common portions (e.g. one apple, one slice of bread) or household measures (e.g. glass, cup, spoon). An average portion size was assigned to each questionnaire item (this portion size is the same for all participants, regardless of their sex or age).
This part asks a set of additional questions including those on the type and brand of breakfast cereal, the type and quantity of milk consumed, the type of fat used in cooking and the amount of visible fat on meat consumed. The questions relating to fat are linked to relevant items in part one and help to estimate the total fat and fatty acid consumption.
FFQ Entry & Calculation Process
The FFQ data were originally entered into an Oracle-based entry system and processed using the CAFE program (Compositional Analyses from Frequency Estimates), which was written in SAS. More recently, the new open source FETA tool has been developed, based on the CAFÉ program. The FETA software, which uses a comma-separated values input file, was written in C and C++ languages, enabling faster processing times than SAS and the C/C++ software and can also be used from the command line. The step-based graphical wizard for running FETA was written in Perl.
In FETA, the frequency category is converted into a portion multiplier (e.g. once a week = 1/7 = 0.14). After multiplication with the portion size, an average daily food weight for each of the 130 FFQ items is obtained. These weights are multiplied by the nutrient composition per gram to obtain the nutrient composition of the actual amount eaten. After summing all FFQ items for a participant, an average daily nutrient intake is obtained. It is recommended that individuals with more than 10 missing lines of data are excluded. The top and bottom 0.5% of the ratio of energy intake to estimated basal metabolic rate are flagged as extreme outliers of nutrient intakes.
For further information on the nutritional analysis of the EPIC-Norfolk FFQ see the CAFE and FETA publications.