Introduction: Food Frequency Questionnaire (FFQ)
Assessment of dietary intake can be estimated through the use of various tools, which differ depending on study objectives, design, and resources. One way is to classify them into prospective and retrospective methods. Another way of classification is into the current diet and food/dietary habits. Typically, assessment of dietary intake through food frequency questionnaires (FFQ) are used in a clinical screening setting or in epidemiologic studies to assess dietary intakes, often in relation to the development of a disease and also to study long-term eating habits.
The first component of the questionnaire is a list of foods, beverages, supplements, etcetera; and the second part is a set of frequency-of-use response categories. Sometimes there is a third part with portion sizes, especially for foods that can easily be quantified, such as a number of eggs, apples, bananas, slices of bread, cups of coffee and tea etcetera.
FFQs are also useful to assess dietary intake in a large sample from different settings, for which a quick and straightforward method is needed to estimate the intake of specific nutrients. FFQs have been established as a practical and cost-effective approach for assessing habitual dietary intake over long periods and in large-scale dietary surveys. The questionnaire can be self-administered or be administered through a short personal interview. The food list may range from a few questions to capture intake of selected foods and nutrients, to a comprehensive list to assess the total diet.
FFQ can be
- Qualitative: with no information on proportion size.
- Semi-quantitative: with standardized portion size estimates OR
- Quantitative: where the respondents estimate portion size.
The major advantages of FFQ are they are simpler, can be administrated quickly, lower in cost and less burden for the respondents when compared to alternative methods.
The dietary information derived from FFQs allows researchers to characterize a cohort-based on nutrient intake, examine the relationships between diet and disease, and diet and other study outcome measures, such as biochemical and functional measures. The questionnaire should also be validated and compared to a gold standard diet analysis technique for the specific population under study. In some cases, FFQ should be country-specific, age-specific and include a comprehensive list of food items to capture the study population’s eating patterns, food choices and diet variability.
Advantages and Disadvantages of assessment of dietary intake by Food Frequency Questionnaire (FFQ) method
- Compared with the other methods, they are not a heavy burden for the volunteers.
- Skilled personnel is not needed.
- Relatively low drop-out rate and avoid interviewer bias.
- In general, they are relatively cheap, can be filled out quickly and are not difficult to analyze.
- Preparation of the questionnaire is a hectic task as it is very time-consuming to construct and validate this type of questionnaire.
- It is almost impossible to obtain the total food intake, which sometimes is forgotten.
- Skilled personnel are crucial when constructing a questionnaire, as well as producing nutrient scores and performing energy adjustments.
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- Health, N. (2010). PART D. Section 1: Energy Balance and Weigth Management. Cancer, 2005-2006.. Pritchard JM, Seechurn T, Atkinson SA. A Food Frequency Questionnaire for the Assessment of Calcium, Vitamin D and Vitamin K: A Pilot Validation Study. Nutrients. 2010 Jul 28;2(8):805–19
- FFQ [Internet]. Available from: ftp://ftp.fao.org/docrep/fao/011/i0351e/i0351e12.pdf