FFQs

FFQs, or food frequency questionnaires, are dietary assessment tools used to estimate an individual's habitual intake of foods and nutrients over a defined reference period, usually several months to a year. They typically present a list of common foods and beverages, with standardized portion sizes and a range of response options for frequency of consumption, from rarely or never to several times per day. Some FFQs are semi-quantitative and ask respondents to indicate portion sizes, while others are qualitative and focus on frequency alone.

Administration can be self-administered, interviewer-administered, or delivered electronically, and FFQs are commonly used in large-scale nutritional epidemiology studies because they are relatively low cost and efficient for ranking individuals by intake. They can be designed to assess total energy intake and intakes of key nutrients or broader food groups, and may be tailored to specific populations or dietary patterns.

Validation and reliability are central to FFQs. They are often evaluated by comparing their results with reference methods such as multiple 24-hour recalls or food records, and with biomarkers when possible. Reproducibility tests assess consistency over time. Calibration studies may adjust FFQ estimates to improve agreement with true intake.

Strengths include suitability for large cohorts, ability to capture habitual intake, and relatively low participant burden. Limitations involve measurement error due to memory, portion size estimation, and food list coverage; potential biases from social desirability or seasonality; and reduced accuracy for absolute intake or for individuals with atypical diets. Regular updates and local adaptation are important for accuracy in diverse populations.