Food frequency questionnaire

Food frequency questionnaire (FFQ) is a dietary assessment tool delivered as a questionnaire to estimate frequency and, in some cases, portion size information about food and beverage consumption over a specified period of time, typically the past month, three months, or year. FFQs are a common dietary assessment tool used in large epidemiologic studies of nutrition and health. Examples of usage include assessment of intake of vitamins and other nutrients, assessment of the intake of toxins, and estimating the prevalence of dietary patterns such as vegetarianism.
Structure and data collected.
Questions.
A FFQ includes questions on a set of food and beverage items. For each food or beverage item, there may be questions asking about the following:
In addition to foods and beverages, FFQs often ask about the frequency of intake and dosages of commonly consumed dietary supplements.
Length and administration format.
A FFQ that aims to capture total dietary intake includes questions on 80 to 120 food and beverage items, and takes 30 to 60 minutes to complete.
FFQs may be interviewer-administered in case of low literacy as well as when being conducted on children.
FFQs are intended for individual rather than household use (i.e., they need to be answered for each individual food consumer). For very young children, the FFQ may be answered by a parent or guardian instead.
Types of FFQs.
FFQs are classified as:
Relation with other assessment tools.
Similar diet assessment tools.
FFQ is a common method for dietary assessment, i.e., for constructing the respondent's diet history. Some other methods include:
Advantages and disadvantages relative to weighted food records.
FFQs, as well as other retrospective diet assessment methods (such as the 24-hour diet recall and other diet history methods) have the advantage that they do not directly affect the behavior of the respondent. In contrast, weighted food records may influence the participant's eating behavior. Weighted food records also carry a high respondent burden.
One disadvantage of FFQs and other retrospective methods is that they may be less accurate because participants are relying on memory rather than information recorded in real time.
Advantages and disadvantages relative to the 24-hour diet recall.
FFQs have the following advantages:
FFQs have many disadvantages:
Validation of FFQs using other methods.
Due to some of the concerns surrounding the validity and reliability of FFQs, research using a FFQ generally also tests the validity of the FFQ. In a typical research design, the FFQ is validated against another dietary assessment technique (such as 24-hour diet recall or weighted food records) on a small population. Once validated, the FFQ can be distributed to a wider population with the same characteristics. The need to validate FFQs against diet recalls or other more reliable methods is a recurrent theme in research and guidance on FFQs.
Food frequency questionnaires in use.
Specificity to populations.
Since FFQs list specific food and beverage items, a FFQ designed for and validated against one population is not valid for other populations. Therefore, FFQs must be appropriately modified and revalidated against new populations. A few key challenges include:
A number of standard FFQs are available for adults in the United States. There is also research based on FFQs in the United Kingdom, although weighted food records are more common there. FFQs have also been developed in Sweden and other Northern and Western European countries. There has been some research on FFQs in other regions, such as the Middle East and Mediterranean, Sri Lanka, and Shanghai, China.
Common FFQs in the United States.
The list below is drawn from existing lists of food frequency questionnaires. All questionnaires in the list below are validated through multiple research studies.
Analysis of data.
Calculation of nutrient intake (for semi-quantitative FFQs).
Calculations for nutrient intake can be estimated via computerized software programs that multiply the reported frequency of each food by the amount of nutrient in a serving of that food. References databases commonly used for this purpose are listed below. Note that to estimate total nutrient intake, it is necessary to include dietary supplements in the FFQ and add the nutrient intake from these, particularly when dealing with populations where the consumption of dietary supplements is common.
For non-quantitative FFQs, nutrient intake cannot be calculated as accurately, but the FFQ can still be used to get a rough idea of nutrient consumption.
Calculation of food groups consumed.
A related use of FFQs is to determine how much people consume broad groups of foods. Examples of such food groups are fruits, vegetables, and added sugars. A useful database for this purpose is the USDA's Food Patterns Equivalents Database (FPED).
Comparison data.
In the United States, data from NHANES is used to provide nationwide comparison data.
Population-level analyses.
FFQs can be used for a variety of population-level analyses:
Criticism.
The low validity of FFQs has made them a subject of criticism. Walter Willett, developer of the Harvard FFQ, estimated a correlation of 0.60 to 0.70 between standard FFQs and diet recalls.
Alan R. Kristal, Ulrike Peters and John D. Potter wrote in their article "Is It Time to Abandon the Food Frequency Questionnaire?" that there was not much scope to learn more from FFQs, and that a more curious and exploratory approach was needed to uncover new insights on diet and its correlation with health status.
The National Cancer Institute has argued that through careful bias correction, some of the limitations of FFQs can be overcome, and they can be very useful.