Pros and cons
Pros
- Low respondent burden - typically take 10-20 minutes to complete
- Assess habitual consumption over an extended period of time
- Comparatively easy to administer and have a low cost compared to other dietary assessment methods
- May be self administered via mail or the Internet
- Used to assess habitual consumption over an extended period of time
- More complete data may be collected if the FFQ is interviewer administered but respondent bias may be less if self-administered
- Can be used to gather information on a range of foods or designed to be shorter and focus on foods rich in a specific nutrient or a particular group of foods e.g. fruit and vegetables
- Portion size estimates can be used to obtain absolute nutrient intakes
- Inclusion of an open section allows respondents to record consumption of foods not included on the food list
- Separate sections can be included that ask about consumption of seasonal items, cooking and preparation methods and additions to foods, including sauces and condiments
- The standardisation of responses enables FFQs to be analysed relatively quickly
- Computer-readable forms can be scanned into computers reducing data-entry errors
- Existing FFQs can be modified for use in new studies if the analysis package is available
Cons
- A comprehensive list of all foods eaten cannot be included and reported intake is limited to the foods contained in the food list
- Accurate reporting relies on respondent memory
- Bias may be introduced with respondents reporting eating ‘good’ foods more frequently (over-estimation) or the consumption of ‘bad’ foods less often (under-estimation)
- A relatively high degree of literacy and numeracy skills are required if self administered, although less than other methods; interviewers can help overcome this problem
- Estimating portion sizes may be difficult and the use of small, medium and large to describe portion size may not have a commonly accepted meaning
- Self-administered FFQs may not be completed fully; some respondents may only complete the questionnaire for items they are familiar with
- Problems with interpreting questions may arise with self-administered FFQs
- FFQs developed in one country or for a specific subpopulation are unlikely to be appropriate for use in another country unless dietary habits are very similar
- The food list may not be reflective of the dietary patterns of the population to be studied; ethnic differences in a population may not be captured for example.
- Pre-prepared meals such as ready meals or take-away foods may not be easy for respondents to classify if the food list is based on more basic food categories
- Validity can vary widely between foods and nutrients from the same FFQ
- Grouping of foods into individual items may make answering some questions problematic