An assessment of validity and reproducibility of two indexes of diet quality.

The Diet Quality Index (DQI) and Healthy Eating Index (HEI) are analytical tools designed to evaluate the overall quality of the total diet. The DQI consists of 8 items, each receiving a score of 0, 1 or 2, to give a maximum score of 16. The HEI consists of 10 items, scored proportionally from 1--10, for a maximum score of 100. DQI and HEI scores were calculated for a sample of women (n = 340) aged 21--80 y enrolled in a longitudinal cohort study of diet, nutrition, and breast cancer. Dietary habits were assessed by at least 3 days of diet records at two time intervals (DR1 and DR2), and a food preference checklist. Venous blood was also collected from fasting subjects for analysis of selected plasma biomarkers. Mean DQI and HEI scores were 10.9 and 77.0 for DR1 and 11.0 and 76.5 for DR2, yielding intraclass correlation coefficients of 0.49 and 0.69, respectively. Higher DQI and HEI scores were strongly correlated (adjusted r > 0.30 in most cases) with higher intakes of foods and nutrients, included both within and outside of the index model at DR1. Higher DQI and HEI scores were correlated with higher plasma levels of alpha-carotene (adj std beta = 0.53, 0.24, respectively), Pbeta-carotene (adj std beta = 0.36, 0.27), beta-cryptoxanthin (adj std beta = 0.39, 0.45), lutein (adj std beta = 0.19, 0.23), and vitamin C (adj std beta = 0.29, 0.30) concentrations, after controlling for BMI and vitamin use. Women in the top DQI and HEI quartiles were more likely to have household incomes in excess of 40K dollars (p < 0.05). Married women with a college education were also more likely to have better diets (p < 0.05 [HEI] and p < 0.10 [DQI]). Higher DQI and HEI scores were linked with higher reported preferences for fruit (HEI and DQI), green vegetables (HEI) and high fat foods (DQI). These data suggest that total diet quality, as assessed by DQI and HEI, correlates with food intakes, demographic variables, food preferences, and biomarker status. Measuring overall diet quality represents a promising new tool for monitoring diet and nutritional status.PhDHealth and Environmental SciencesNutritionPublic healthUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/132797/2/9990903.pd