The study of the relation between diet quality and diet cost among different strata of the US population has been made possible, for the first time, by the release of the national food price database by the USDA Center for Nutrition Policy and Promotion (CNPP) in May 2008. The prices were for foods consumed by the participants in the representative population-based 2001-2002 National Health and Nutrition Examination Survey (NHANES). The NHANES data include a 24-hour dietary recall, a medical examination and completed detailed demographic and health questionnaires. Linking the food price vector ($/100g) with the national Food and Nutrient Database for Dietary Studies (FNDDS 1.0) will allow for the estimation of the monetary value of the diet ($/day and $/2000kcal) at the individual-level, in parallel with the estimation of dietary exposure variables commonly used in studies of diet-disease associations. Being able to link diet costs with the NHANES dietary, demographic, socioeconomic and biomarker data for 5,411 US adults (agee20) will permit a rare first look at the intermediate mechanisms in the model framework that links socioeconomic position (SEP) and health outcomes. Energy and nutrient intakes will be used to calculate energy density and nutrient density of each respondent's diet. The new measure of energy-adjusted diet cost may help explain the observed social gradient in obesity, type II diabetes and the metabolic syndrome. Analyses will identify SEP predictors of dietary energy density, diet quality and energy-adjusted diet cost and will elucidate the relations among them, something that has never been done in a large-scale representative sample of US adults. The primary hypothesis is that diet quality and cost will be inversely linked;however the nature of that relation will differ by gender, race/ethnicity and SEP strata. The second series of analyses will provide descriptive data on diet quality and cost for subgroups of interest, including high-risk and vulnerable subgroups of the US population, including food assistance recipients or individuals with established chronic disease. Within the limitations of a cross-sectional study, analyses will explore the relation between diet quality measures, diet cost and health outcomes, including measured body mass index (BMI), biomarkers of inflammation, individual components of the metabolic syndrome (e.g., diabetes, abdominal obesity, dyslipidemia, high blood pressure, insulin resistance, prothrombosis and inflammation), the metabolic syndrome and diabetes. Many of those have been linked to specific components of the diet. The hypothesis is that some of the observed associations between dietary components and health will be attenuated once energy-adjusted diet costs are included in the model. The proposed studies offer a unique first look at the cost of healthful and unhealthful diets in the US and the consequences of food pricing on health.
The purpose of this research is to assess the relationship between the cost and quality of diets consumed by groups differing in socioeconomic and demographic characteristics. The study is made possible by new data on national food prices that will be merged with a population-based dietary intake survey. This work addresses economic barriers to nutritious diets and thus provides a vital part of the research on socio-economic disparities in health. The long term goal of this research is to establish a new approach to estimating diet cost that links directly to estimates of nutrient intake. The approach will allow investigators to assess food cost as a factor influencing the dietary behaviors of individuals and large populations.
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