Intersections of Educational Attainment, Indigenous Identity, and Race/Ethnicity Best Predicted Diet Quality Among Adults in Canada: A Conditional Random Forests Analysis

BACKGROUND: Although it is well-known that diet quality varies according to multiple dimensions of socioeconomic position (SEP), much remains unknown about how these dimensions together shape diet quality. Given that diet quality associated with 1 SEP dimension (eg, income) can systematically differ across another dimension (eg, race and ethnicity), it is necessary to investigate diet quality across SEP intersections. OBJECTIVES: The aim of this study was to identify SEP intersections that best predicted lower and higher diet quality among adults in Canada. DESIGN: Population-based data were from the cross-sectional 2015 Canadian Community Health Survey-Nutrition. Data were collected by interviewers who visited selected dwellings to collect household information and administer a general health questionnaire and a 24-hour dietary recall. PARTICIPANTS/SETTING: Data from 13 617 adults aged 18 years and older living in Canada's 10 provinces. MAIN OUTCOME MEASURES: Twenty-four-hour dietary recall data were used to assess diet quality based on the Healthy Eating Index-2015 (HEI-2015) score (range, 0 to 100). STATISTICAL ANALYSES PERFORMED: Conditional random forests, a supervised machine-learning technique, were used to identify 4 of 12 SEP indicators that best individually predicted HEI-2015 scores. The resulting 4 most important predictors were used to predict diet quality using all possible 2-way intersections. RESULTS: The 4 most important intersectional predictors of HEI-2015 scores based on conditional random forest variable importance measures were (1) educational attainment and Indigenous identity and race/ethnicity, (2) educational attainment and household food insecurity, (3) educational attainment and sex/gender, and (4) household food insecurity and sex/gender. Among these 4 SEP intersections, individuals without a high school diploma living in a severely food-insecure household had the lowest (55.7), and individuals without a high school diploma identifying as Middle Eastern had the highest (64.5) predicted HEI-2015 scores. CONCLUSIONS: The SEP intersection defined by educational attainment and Indigenous identity and race/ethnicity was the most important predictor of diet quality among adults in Canada.