Food frequency questionnaires (FFQ)
Retrospective method where the participant reports frequency of usual consumption of a specific food/food group over a pre-defined period of time.
Questions on quantity can also be included (semi-quantitative FFQ or fully-quantitative FFQ).
The number of food/drink items included in the FFQ vary and can be long (comprehensive FFQ) or short. It can be administered in person or over the phone or self-completed on paper or online.
The strengths and weaknesses are detailed in the table below:
| Strengths | Weaknesses |
|---|---|
| Can capture usual intake retrospectively | Precision of intake estimates is reduced |
| Can capture foods consumed irregularly | Information is limited to the food/food groups included in the food list; this can decrease cross-cohort comparison especially when diverse cultures are being compared |
| Can rank participants into intake levels | Short FFQs may not be reliable for total diet/nutrient intakes |
| If a long FFQ is used and portion size estimated, usual dietary intake and total nutrient intake can be estimated | Relies on good participant generic memory and literacy and numerical skills |
| Low participant burden so useful in large population studies | Needs careful design and validation in the population of interest as prone to misreporting |
| Low researcher burden as coding is less intensive than recall or diet diaries |