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Lower-Energy-Density Diets Are Associated with Higher Monetary Costs per Kilocalorie and Are Consumed by Women of Higher Socioeconomic Status

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Abstract

Objective

Diets of lower energy density are associated with higher diet quality, lower body weights, and better health outcomes. This study examined associations among dietary energy density, energy-adjusted diet costs, and socioeconomic indicators of study participants.

Design

In this cross-sectional study, energy and nutrient intakes for 164 men and women aged 25 to 65 years were obtained using a food frequency instrument between June 2005 and September 2006. Dietary energy density (kcal/g) was calculated with and without beverages. Energy-adjusted diet costs ($/2,000 kcal) were calculated using food prices in Seattle, WA. Tertile splits of energy density and energy cost were analyzed using tests for linear trend. Linear regression models tested the association between education, income, and dietary variables, adjusting for age and sex.

Results

Diets of lower energy density were associated with higher absolute nutrient intakes. Diets of lower energy density were also associated with higher energy-adjusted diet costs. Conversely, highest energy density diets were associated with lower intakes of micronutrients and fiber and lower costs. Education and household income showed a negative association with dietary energy density in regression models. Education and household incomes showed a positive association with the energy-adjusted cost of the diet. Education was a stronger predictor of both energy density and energy cost than was household income.

Conclusions

Higher-quality diets were not only more costly per kilocalorie but were also consumed by persons of higher educational level. The influence of diet quality on health, observed in some epidemiologic studies, might be modulated by unobserved indexes of socioeconomic status.

Section snippets

Participants

The study was based on a stratified sample of faculty and staff of a large public university in the Pacific Northwest. The sampling frame was stratified by ranges of university salaries, obtained from the publicly available payroll system. There were 20 salary strata, with means ranging from $1,408 per month to $13,924 per month, with participant recruitment based on random sampling within each strata. Whereas salary data were used for targeting recruitment letters, the key income variable in

Study Participants

More than 3,000 introductory letters were sent to preselected respondents via campus mail. Of these, 350 persons responded by mail or by telephone and, depending on work schedules and other commitments, 259 were invited to attend an introductory orientation meeting and provide consent. Persons who never began study protocols; those who dropped out in the course of the 5-week study; those who failed to complete all questionnaires, including FFQs and diet records, or who did not keep food

Discussion

Lower-energy-density diets were associated with higher nutrient intakes. In contrast, the more energy-dense diets contained more total fat and saturated fat but were lower in fiber and micronutrients. These findings that energy density and nutrient density of diets are inversely linked are entirely consistent with past data, based on much larger populations, and representative samples in the United States (10) and in France (34, 35).

Our analyses included an important and sometimes

Conclusions

The finding that higher-quality diets were consumed by women of higher SES and are more costly per 2,000 kcal has implications for epidemiologic studies of diet and chronic disease. Nutritional epidemiology has historically been based on the premise that nutrient exposures are directly linked to health outcomes. However, nutritional status is also intimately linked to SES (52) and the findings reported here raise the possibility that the higher monetary cost of nutritious diets may provide one

P. Monsivais is research analyst and investigator, Nutritional Sciences Program, School of Public Health, University of Washington, Seattle

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    P. Monsivais is research analyst and investigator, Nutritional Sciences Program, School of Public Health, University of Washington, Seattle

    A. Drewnowski is professor and director, Nutritional Sciences Program, School of Public Health, University of Washington, Seattle

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