Objective/design: Time and budget constraints limit nutrition evaluation in Canadian health surveys. To encourage regular population diet monitoring in Canada, we developed and assessed the relative validity of a population-based food frequency questionnaire (FFQ) to assess usual diet in Quebecers. A 73-item, self-administered semiquantitative FFQ was designed in French and English from the Block National Cancer Institute Health Habits and History Questionnaire to capture usual food consumption among Quebec adults. The US Department of Agriculture Healthy Eating Index (HEI) (maximum score=100) was adapted to Canadian age- and sex-specific dietary recommendations, validated, and programmed to score the FFQ for diet quality.
Subjects: The FFQ was pretested, pilot tested, and administered by mail to a random sample of 248 adults aged 18 to 82 years in the Montreal area (57% women) who were recruited by random digit dialing (64% response rate). A subgroup (n=94) furnished four nonconsecutive 1-day food records for validation of the FFQ.
Results: Mean FFQ energy intakes were 2,216 kcal (median 2,110 kcal) for men and 1,785 kcal (median 1,680 kcal) for women. Proportional median macronutrient consumption was similar in both sexes at 17% protein, 34% to 35% fats, and 48% to 49% carbohydrates, but differed by age group in women. Adequacy of micronutrient intakes relative to Dietary Reference Intakes varied by age, sex, and nutrient. Whereas most mean or median intakes were at or exceeded recommendations, calcium intakes were low overall and levels of several other nutrients were very low at the 10th percentile. Mean Canadian HEI (range 46 to 99) was higher in women (74.9) than men (70.3, P<.001). Women's scores showed they met recommendations for intakes of vegetables and fruit, cholesterol, and sodium better than men (P ranged from <.01 to <.0001), while men fared better at meeting recommended fat intake levels (P<.05).
Conclusions: The Canadian HEI adequately discriminates overall diet quality based on dietary data estimated from our FFQ. Examination of subscores within and between quartiles may best reveal which food groups require attention to improve diet quality, providing valuable information for teaching and planning. Future studies should test diet quality indicators in populations recruited to reflect greater dietary diversity and reporting ability and include members of disadvantaged groups to provide a broader set of behaviors that could shed light on factors influencing diet quality.