Development of a dish-based food frequency questionnaire for Iranian population

Background: Food frequency questionnaires (FFQs) are widely used in large studies worldwide. They usually seek to rank people according to their usual food intake rather than a specific period of time. In the present study, we aimed to develop a dish-based, semi-quantitative FFQ to seek habitual diet of general population aged 9 to 65 years in Tehran. Methods: To develop the FFQ, four main steps were taken. At the beginning a list of commonly consumed Iranian foods and mixed dishes was prepared. To prevent excessive questionnaire length, some food items were grouped. Then, reference portion sizes were defined for each mixed dish in the list. The portion sizes were defined either based on the most common food portions reported in existing data or based on conventional portioning. In the third step the frequency response for consumption of food items and mixed dishes were determined. In the last step, recipes were developed for mixed dishes based on several data sources, including previous surveys. Finally, the content validity of the questionnaire was evaluated by the expert panel. Results: The final food list of the FFQ comprised 142 food items and mixed dishes in six major food groups, including dairy products, breads, mixed dishes, dried fruits, nuts and seeds, fruits and vegetables, and miscellaneous food items and beverages. Nine frequency response options for all food items varying from "never or less than once per month" to "more than 6 times a day" were considered. A portion size was included for each item, whether food items or mixed dishes. Conclusion: As Iranian food recipes are typically characterized by various ingredients it is very difficult for the respondent to recall the amount and type of the ingredients. Likewise, information about cooking methods beside ingredients of foods are important to estimate their nutritive values, which can be explored only through asking about consumption of mixed dishes. The current FFQ was developed to overcome the mentioned problems. It can be applied in nationwide studies in which foods and/or nutrients are predominant determinant of health and/or diseases.