Energy density, energy costs and income - how are they related?

OBJECTIVE To examine the association between energy density and energy costs in single food items and composed diets, and to explore differences in energy density and energy cost between income levels. DESIGN A cross-sectional study using data from two Dutch cohort studies and recent national food prices. Food prices were retrieved from two market leader supermarkets. Data on dietary intake were measured using a computerized face-to-face interview (cohort 1) and 24 h recalls (cohort 2). SETTING The Netherlands. SUBJECTS A sample of 373 young adults from the Amsterdam Growth and Health Longitudinal Study (AGHLS, measured in 2000) and a sample of 200 community-dwelling elderly from the Longitudinal Ageing Study Amsterdam (LASA, measured in 2007). RESULTS We found significant inverse associations between energy density and energy costs in single food items (r = -0.436, P < 0.01) and composed diets (AGHLS men r = -0.505, women r = -0.413, P < 0.001; LASA men r = -0.559, women r = -0.562, P < 0.001). Furthermore, we found that people stratified into higher energy density quartiles consumed significantly more energy per day, less fruits and vegetables, and had significantly lower diet costs. Explorative analyses on income did not reveal significant differences regarding energy density, costs, or fruit and vegetable intake. CONCLUSIONS In the Netherlands also, energy density was inversely related with energy costs, implying that healthier diets cost more. However, we could not find differences in energy density or costs between income levels. Future research, using precise food expenditures, is of main importance in studying the economics of obesity and in the aim of making the healthier choice easier.