Description of the Questionnaire

This Food Frequency Questionnaire (FFQ) is designed to record an individual’s dietary habits over the past 12 months. It includes foods and beverages commonly found in the Mediterranean and Greek diet. The participant is asked to indicate the frequency of consumption for each food item by selecting one of the following categories: Never or almost never, 1 to 3 times per month, Once per week, 2 to 4 times per week, 5 to 6 times per week, Once per day, 2 to 3 times per day, or 4 or more times per day.

Purpose

The purpose of this questionnaire is to record and quantitatively assess the frequency of consumption of key food groups by the participant, to evaluate adherence to healthy dietary patterns such as the Mediterranean diet, and to explore associations between dietary habits and health indicators or the occurrence of chronic diseases.

Data Analysis and Use

The collected data are converted into daily or weekly quantities based on the reported frequency and standard portion size for each food item. Analysis involves categorizing foods into dietary groups such as fruits, vegetables, dairy, meat, fish, cereals, and fats. Through mathematical algorithms or dietary analysis software, total calories, macro- and micronutrients are calculated, along with composite dietary indices such as the Mediterranean Diet Score or the Healthy Eating Index. The data can then be incorporated into statistical models to evaluate correlations with health indicators, biochemical results, or other variables.

Data Usage

The results of the FFQ are widely used in population-based epidemiological studies to examine the association between dietary patterns and health outcomes, in the design and monitoring of dietary interventions, in dietary surveillance and public health policy studies, and in clinical research evaluating participants’ adherence to nutritional guidelines or protocols.

Calibration

Calibration of the questionnaire is carried out through a pilot application in a representative sample, and results are compared to alternative methods of dietary intake assessment, such as repeated 24-hour dietary recalls, 3- or 7-day food diaries, and biochemical intake markers (such as blood levels of vitamins or fatty acids). Statistical validation of the tool’s accuracy and reliability includes the use of Pearson or Spearman correlation coefficients, repeatability coefficients, and graphical methods such as Bland-Altman plots.

References

Katsouyanni K. et al. (1997). European Prospective Investigation into Cancer and Nutrition (EPIC): Validity and reproducibility of a food frequency questionnaire in Greek population. Public Health Nutrition, 1(1), 47–58.
Willett W. et al. (1985). Reproducibility and validity of a semiquantitative food frequency questionnaire. American Journal of Epidemiology, 122(1), 51–65.
Trichopoulou A. et al. (2003). Adherence to a Mediterranean diet and survival in a Greek population. New England Journal of Medicine, 348(26), 2599–2608.
Cade JE, et al. (2002). Development, validation and utilisation of food-frequency questionnaires – a review. Public Health Nutrition, 5(4), 567–587.