Food Frequency Questionnaire (FFQ)
FOOD FREQUENCY QUESTIONNAIRES
Food Frequency Questionnaires (FFQ) are a type of dietary assessment instrument that attempts to capture an individual’s usual food consumption by querying the frequency at which the respondent consumed food items based on a predefined food list. Given that food lists are culturally specific, FFQs need to be adapted and validated for use in different contexts.
FFQs are the most common method of measuring dietary patterns in large epidemiological studies of diet and health. FFQs are often limited to the food items that are a source of nutrients related to the particular dietary exposures under study, for example fruit and vegetable consumption or foods with high levels saturated fat. Dietary diversity indices are a type of FFQ, as are many types of food consumption modules included in household consumption and expenditure surveys, which are frequently based on food lists.
FFQ recall periods vary greatly, but typically range from 7 - 30 days (though some are as long as 1 year). In general, FFQs rely on a longer recall period in order to capture foods that are not consumed every day but are still part of the individual’s typical diet. These measures of ‘usual intake’ are a more valid indicator of the relationship between diet and health outcomes than those capturing only a single 24-hour snapshot of the diet. (However 24-hour dietary recalls can provide information on the usual intake if data are collected on two non-consecutive days from respondents.)
While FFQs typically collect information on the frequency of consumption they do not typically collect information on the quantity consumed. A semi-quantitative food frequency questionnaire (SQFFQs), a variant of the FFQ, does include questions about portion sizes consumed. However, because foods are not typically weighed or measured using household utensils, SQFFQs are not as accurate as other quantitative dietary assessment methods (e.g. 24 hour recall), but have the benefit of providing quantitative information on usual intake.
- Estimates the ‘usual diet’ by using a longer recall period
- Captures individual-level dietary patterns
- FFQs can be easier and less time-consuming to implement than a 24-hour recall, if the food list is relatively short (i.e. <100 items)
- FFQs require substantial up-front investment to develop and validate the instrument for a given context
- In the case of FFQs and SQFFQs, usual frequency of intake is prone to measurement error, particularly with recall periods longer than 7 days (and usual portion size questions are prone to measurement error in the case of SQFFQs)
- Long FFQs (i.e. those with 100+ items) can take longer to administer than a standard 24-hour recall
- FFQs do not provide a precise quantitative measure of nutrient intake
- To capture seasonal variation, the survey must be repeated in multiple seasons (unless FFQ is based on consumption over the past year)
Key take-away points: Methods and types of indicators that can and cannot be derived with these data
There are a number of ways that FFQ data can be leveraged for food security and nutrition analyses. Some specific examples of how they can be used include:
- Particularly good for estimating the usual diet and for understanding the relationship between certain consumption patterns and health outcomes
- Useful for assessing suitable vehicles and fortificant levels, as the food list can be tailored to include all
significant sources of micronutrients
- Useful for monitoring reach and coverage, as FFQs can specify brand names of fortified foods
- Major limitation is that they need to be created and validated for use in different countries/contexts
1) Coates et al. (2012), Applying Dietary Assessment Methods for Food Fortification and Other Nutrition Programs: http://www.harvestplus.org/sites/default/files/Dietary%20Assessment%20Methods_Sept%202012.pdf