Researchers from Wageningen University & Research (WUR) developed sum scores for the Food Frequency Questionnaire (FFQ) from adult participants. The FFQ consists of one basic questionnaire covering the macronutrient intake (heart of the flower) which has been assessed at 1A and three shorter questionnaires (the petals) covering (micro)nutrients assessed at 1B, 1C, and 2A. (sections: nutrition (Flower FFQ) and secondary & linked variables))
Using the FFQ Sum scores from 1A, an ultra-processed food categorization has been generated and is available for use as well.

The FFQ sum scores can be requested in the Lifelines catalogue. When this data has been used in your research, you will have to include a reference to the following paper:

• Siebelink, E., Geelen, A., & de Vries, J. H. (2011). Self-reported energy intake by FFQ compared with actual energy intake to maintain body weight in 516 adults. British journal of nutrition, 106(2), 274-281.

Optional paper for complete FFQ questionnaire:

• Baart, A. M., Brouwer-Brolsma, E. M., Perenboom, C. W., de Vries, J. H., & Feskens, E. J. (2022). Dietary Intake in the Lifelines Cohort Study: Baseline Results from the Flower Food Frequency Questionnaire among 59,982 Participants. Nutrients, 14(1), 48.

A Food Frequency Questionnaire consists of a foodlist with a frequency response section for subjects to report how often each item was consumed over a specified period of time (in this case: one month). Data collection is therefore retrospective. From the answers given in a FFQ, nutrient intake can be estimated by calculations made with computerized software programs that multiply the reported frequency of each food item by the amount of nutrient in a serving of that food. A reference database is used to establish the nutrient content of each food item. FFQ data are assumed to be representative of habitual intake and can be used to rank individuals according to intake.

Lifelines participants aged 18 years and older complete four questionnaires on their food intake: one main questionnaire at baseline to estimate energy and macronutrient intake and three questionnaires on specific (micro)nutrients, i.e. a questionnaire on b-vitamins (questionnaire A), one on fatty acids (questionnaire B), and a vitamin ACE questionnaire (questionnaire C). The information from the questionnaires on specific nutrients can only be interpreted by combining this information with the information from the main questionnaire at baseline.

From the food intake as reported in the total FFQ, the following information was calculated:

1. The intake in grams of all foods included in the FFQ per person per day.
2. The energy, macronutrients and micronutrients delivered by these foods.
3. The total energy, macronutrient and micronutrients intake per person per day.

The questions on the intake of a certain food group generally consist of three parts:

1. The frequency of consumption is reported in days per week
2. The number of servings per day on days that the specific food was eaten is specified
3. The types of the food consumed are reported (for example: white chocolate, milk chocolate and dark chocolate)
   

To calculate the absolute intake of foods in grams per day the following formula was used: frequency of consumption * number of servings * serving size (* food item * correction factor serving size)

Preprocessing:

• Frequency of consumption: it is assumed that a month includes 28 days (reference periode is 4 weeks). The frequency 'one day per week' will therefore receive the value 0.14 (4/28)
• Food items eaten within a food group are assigned a value according to the frequency of their consumption: never = 0, sometimes = 0.33, often = 0.67, always = 1.
• Contributions of every food item to the total consumption within the food group are recalculated so that they add up to 1, in order to make them evenly distributed.
• Serving size and correction factor serving size are based on external sources (NEVO table 2011).

When the consumption of each food item as included in the FFQ was calculated in grams per day, the consumed amount in grams was multiplied by the nutrient content of that food item as reported in the NEVO table 2011, in order to calculate the nutrient intake for each participant on a food level.

The total energy, macronutrient and micronutrient intake per person per day is calculated by adding up the energy and nutrient intake through all separate food items included in the FFQ for each participant.

The WUR researchers listed the following points of attention:

• Extreme values have not been corrected: Answers given to general questions on the diet as included in each FFQ questionnaire may be used to explain extreme values, but they have not been used to correct for extreme values in any way. It is up to individual researchers to include or exclude participants with extreme values in their analyses.
• Not all missing values are treated equally: When frequency of consumption is missing, the whole question cannot be interpreted and data for this food are not included in the calculations of total nutrient intake. Resulting in the possibility of underestimation of total daily intake of some nutrients for this participants. When the number of servings and/or the food items consumed are missing, standard answers are used for calculations (according to the Dutch National Food Consumption Survey 1998). Because these are standard answers established for the whole population, the consumption of the food in grams per day and the intake of certain nutrients may be over- or underestmiated.

• Brouwer-Brolsma, E. M., Perenboom, C., Sluik, D., van de Wiel, A., Geelen, A., Feskens, E. J., & de Vries, J. H. (2021). Development and external validation of the ‘Flower-FFQ’: a FFQ designed for the Lifelines Cohort Study. Public Health Nutrition, 1-12.
• Brouwer-Brolsma, E. M., Streppel, M. T., Van Lee, L., Geelen, A., Sluik, D., Van de Wiel, A. M., ... & Feskens, E. J. (2017). A National Dietary Assessment Reference Database (NDARD) for the Dutch population: rationale behind the design. Nutrients, 9(10), 1136.

Below the total intake per person per day for different energy/macronutrient/micronutrient variables are listed.

* All FFQ sum scores included as assessment 'sec' as the sum scores include several assessments.