Over the past several decades diet-related chronic diseases (DRCDs), including cancers and cardiovascular diseases, increased worldwide (World Health Organization, 2003). Understanding the relationship between dietary factors and DRCDs can lead to cost-effective and science-based disease prevention and management strategies.
Food Frequency Questionnaires (FFQs) are the most commonly used dietary assessment tool in nutritional epidemiological studies because they are cost-effective, easy to administer and are thought to give reasonable estimates of long-term usual intake—see figure below.
Example of a food frequency questionnaire (Modified from Park, 2011, 204)
Individual dietary intakes vary from day-to-day for many reasons, including age, socioeconomic background (food costs and availability), days of the week, food preference and behavioral factors (Beaton et al, 1979, 1983; Gwon et al, 2004; Willet, 2013). Sex and gender are also important diet-determining factors, but these have not been prospectively considered in the development, validation, and implementation of FFQs. Searching PubMed with various combinations of the keywords “FFQ,” “Food Frequency Questionnaire,” “Validation,” and “Validity” yielded 1,124 articles published between January 1983 and May 2014. Excluded were studies conducted in one sex or with subjects other than healthy adults, review articles, articles published in languages other than English, and articles that could not be found through web searches. The resulting 246 validation studies were examined to identify the development process of FFQs used in each study. Among them, only 148 articles described the development process of the FFQ. Since some FFQs were validated more than once, 48 studies that developed FFQs were identified for the remaining validation studies. Therefore, a total of 196 FFQ development studies were analyzed: only 21 studies (10.7%) were found to have considered sex in the development phase of FFQ. The sex of the survey subject was reported more often in determining portion sizes (7.7%) than in selecting food items or “dish” (5.6%). Among the 246 validation studies, only 36.6% reported the results by the sex—see chart below.
Sex of Subject Reported in the Development and Validation Studies of FFQs published between January 1983 and May 2014.
Gendered Innovation 1: Analyzing Sex in Portion Size Increases Accuracy in Dietary Assessment
The Fourth Korean National Health and Nutrition Examination Survey (KNHANES IV) conducted 2007-2009 (Korea Centers for Disease Control and Prevention, 2010) revealed differences between men and women (over age 30 years) along two dimensions important in FFQ development: 1) portion size (influenced by sex), and 2) dish selection (influenced by gender). Analyzing portion size revealed that sex and gender interact: men usually eat larger portions of selected foods, such as steamed rice, a staple of Korean diet. Women, by contrast, chose to eat larger portions of fruits and vegetables, such as oriental melon—see figure below. Dishes consumed frequently also differed by gender (data not shown). These sex and gender differences will impact major sources of energy and nutrients.
Distribution of portion sizes of selected dishes by sex. Men eat larger portions of rice; women eat larger portions of oriental melon. Data from the KNHANES IV 2007-2009 were reanalyzed.
Considering how sex and gender interact is important for identifying the association between diet and cancer. A dish-based FFQ was developed to study diet and cancer associations (Park et al., 2011). One-hundred and twelve dish items were selected considering the amount and frequency of consumption, contributions to energy, nutrients, and cancer-related dietary factors (CRDFs) suggested by the World Cancer Research Foundation (2007). Three portion sizes were assigned for each dish. When the portion size of each dish was re-evaluated by sex, portion sizes of 94 dishes (84%) differed significantly between men and women, 73% of the items were larger in men than in women (Noh et al, unpublished data). These results led to the development of sex-specific portion sizes for all items on the FFQ. A corrected FFQ was developed for each sex.
The original FFQ developed by Park et al. (2011) was validated in a study with 288 adults that consisted of 115 men and 173 women (50% more than men) against 12-day diet records collected over one year (Park et al., 2012). The dataset and the procedures were reexamined after correcting the portion sizes between men and women—while holding dishes available for selection constant.
FFQ validation data can be reevaluated retrospectively to analyze sex
- 1. Data are disaggregated by sex.
- 2. Dish items on FFQ are corrected for portion sizes for each sex.
- 3. Intakes of energy, macronutrients, and CRDFs are corrected for each sex.
- 4. Corrected data are compared to original data to yield a better understanding of dietary intakes.