Background: Food prices are an established determinant of food choice and may affect diet quality. Research on diet cost and diet quality in representative populations has been hindered by lack of data.

Objective: We sought to explore the distribution of diet cost and diet quality among strata of the US population and to examine the association between the 2 variables.

Design: In this cross-sectional study, monetary costs of diets consumed by participants in the 2001-2002 NHANES were estimated with the use of a national food price database. Healthy Eating Index (HEI)-2005 values were estimated with the use of the population ratio method for the calculation of average scores. Mean daily diet costs, energy-adjusted diet costs, and HEI-2005 scores were estimated for subpopulations of interest. Associations between energy-adjusted diet cost, HEI-2005 scores, and HEI-2005 component scores were evaluated.

Results: Higher energy-adjusted diet costs were significantly associated with being older and non-Hispanic white, having a higher income and education, and living in a food-secure household. Higher diet costs were also associated with higher HEI-2005 scores for both men and women. Women in the highest quintile of diet costs had a mean HEI-2005 score of 69.6 compared with 52.5 for women in the lowest-cost quintile. Higher diet cost was strongly associated with consuming more servings of fruit and vegetables and fewer calories from solid fat, alcoholic beverages, and added sugars.

Conclusion: Given the observed association between diet cost and diet quality, helping consumers select affordable yet nutritious diets ought to be a priority for researchers and health professionals.