Dietary intake assessment - Frequent food questionnaire

FFQ image

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Population of Interest (P=Parent, R=Researcher, C=Child)

  • Age: 1-10 yrs (P); 3-5 yrs (P); 10-12 yrs (P and/or C); 12 yrs+ (C)
  • Setting: Clinical; Home; Community; Population
  • Administration Method: Self Report; Face to Face (?); CATI

Tool

This is a questionnaire that asks participants to report the frequency of consumption of a defined list of foods, which may or may not include information on portion size in order to estimate the intake of one or several specific nutrients. An FFQ usually has a reporting period greater than 24 hours (eg. week/s, month/s, year/s)

Validity

The validity of an FFQ improves with a more detailed food list that is appropriate to population.

Reliability

Higher values of dietary intakes usually occur with first administration.

When to use

To rank respondents by intake level and predict individual level health outcomes. Depending on age of child, an FFQ can be self completed for children >8yrs or may be parent-completed. FFQ's should not be used for assessing absolute energy and nutrient intake at the individual level.

Bias

FFQ’s generally overestimate habitual energy intake. First administration of FFQ results in higher energy and nutrient intakes and greater frequencies of consumption than subsequent administrations

Burden

Low participant burden, cheap to administer.

Considerations (miscellaneous)

An FFQ has the ability to estimate intake over the extended period of time, so is more appropriate for dietary programs aiming to develop long-term behaviour change. These methods do not provide precise estimates of absolute nutrient intake, but classify subjects on the basis of their positions relative to others - assigned by quantile ranks. The development of the food list is crucial to a successful and reliable data collection. It is difficult to develop a comprehensive list including enough but not too many food items so that respondents of very different eating habits can find the right answer. Ideally, the food list has to be adapted to the studied population. To comprehend the FFQ children usually have to be older than 12 years. The most practical and economical method for collection of comprehensive dietary data in large epidemiologic studies is the food frequency questionnaire (FFQ). Compared with other approaches, such as 24-hour recalls and food records, the FFQ generally collects less detail regarding the foods consumed, cooking methods and portion size. Therefore, the quantification of intake is not considered as accurate. However, unlike records or recalls, FFQs are designed to capture usual dietary intake but is dependent on the reference period. Most are completed independently by a respondent and are relatively inexpensive. Therefore, the FFQ is usually the method of choice in large-scale epidemiological studies.

Strengths

  • Relatively inexpensive
  • Quick to complete
  • Lower respondent burden
  • Can assess current or past diet
  • Suitable for large-scale surveys
  • Can be self administered, posted or online
  • Short versions can focus on specific nutrients with few food sources.
  • Allows ranking of individuals by food or nutrient intakes so that characteristics of those with high and low intakes may be compared
  • Usual eating patterns are not affected.

Limitations

Biases caused by errors in memory, perception, conceptualization of food portion sizes. Daily variation in diet not usually assessed. Dependent on regular eating habits. Food composition tables used to estimate nutrient intake. Requires validation in relation to reference measure. Literacy and numeracy skills needed if self-completed by child. An FFQ does not allow quantification of absolute intake of individuals.