Association between Food Swamps and the Diet Quality of Household Food Purchases in a Nationwide Sample

Abstract

Background: Food swamp is a term for local food environments where there exists a higher density of unhealthy food retailers selling more energy-dense, nutrient-poor food offerings relative to healthier options. Those living in a food swamp have been found to have higher rates of negative health outcomes compared to those living outside a food swamp, but the mechanism for this relationship is unclear. Objective: To examine the association between living in a food swamp and the diet quality of household food purchases in a cross-sectional analysis of a nationwide sample. Methods: Data from the National USDA Household Food Acquisition and Purchase Survey (2012-2013; n = 4,692 households) were analyzed, which included a detailed collection of all foods purchased in the household for one week. The physical food environment index, which we termed the “food swamp score” was calculated for each household as the ratio of the counts of unhealthy food retailers to the counts of all food retailers for a 1-mile radius around the home for urban households and a 5-mile radius around the home for rural households. Healthy eating index (HEI) scores were calculated for the total of each household’s food purchasing, providing a 0-100 score of the healthfulness of all foods purchased at food stores and restaurants. Linear regression models were used in the primary analysis to examine the association between quintiles of the food swamp scores and the healthy eating index (HEI) scores for each household, stratifying by urban versus rural census tract and controlling for covariates, including race/ethnicity, education, overall health status, household income, household car ownership, household food security, and supplemental nutrition assistance program (SNAP) participation. Secondary analyses included further stratifying models by car ownership. Results: The mean household HEI score across all households was 53 (SD = 14), and the mean food swamp score across all households was 89 (SD = 20). No statistically significant associations were found between household food swamp score quintiles and HEI scores of weekly household food purchases when adjusted for covariates for households in either urban or rural census tracts. No statistically significant associations were found when further stratifying these models by car ownership. Conclusion: We found no association between the food swamp score and the dietary quality of all household food purchases in a nationally representative sample with a detailed collection of all food purchases.