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January 25, 2011

Higher costs of more nutritious diets contribute to socio-economic disparities in health

Socio-economic disparities in diet patterns and nutrient intake are well documented in research. People with lower incomes and less education typically have less healthful eating habits than people with higher incomes and more education. But little is known about the extent to which those disparities are driven by higher monetary costs of nutritious foods.

Now, a new study from UW researchers concludes, for the first time, that socio-economic disparities in diet quality are directly affected by diet costs. The study, “Are socio-economic disparities in diet quality explained by diet costs?” is published in advance online in the Journal of Epidemiology & Community Health.

UW researchers have previously found that better quality diets are more costly than less nutritious diets, and that there is a rising disparity in the price of healthful foods. “The twist with this new study is that we’ve connected  the dots that could explain why people in a lower socio- economic status have less nutritious diets,” said Pablo Monsivais, UW acting assistant professor of epidemiology.

Monsivais, with Program Manager Anju Aggarwal and UW Professor Adam Drewnowski, studied data of more than 1,300 men and women from the Seattle Obesity Study, a population-based study of food access, diet quality and health among King County, Wash. residents.

The researchers first looked at how diet cost was associated with educational attainment and household income, two indicators of socio-economic position. They used statistical methods to control for total calorie intake and other factors. The average diet cost was higher for people with higher educational attainment and higher household income.

People with lower educational attainment had diet costs that were an average of $1.09 per day lower than that of persons in the highest group ($8.19 to $9.28 per day).

People with the highest educational attainment or income also enjoyed the most nutritious diets. Those in the highest income group reported diets that were on average 9.3 points higher in nutrient density than diets reported by the lowest income group (96.6 versus 87.3 percent), after controlling for dietary and demographic factors.

However, after taking the cost of food into account, the difference in dietary nutrient density between the highest and lowest groups shrank to 1.4 percentage points (93.0 versus 91.6 percent). “These results tell us that cost is a major factor in explaining the differences in eating habits between people of lower and higher socioeconomic level,” said Monsivais.

Monsivais said the Seattle study should be replicated on a wider, more diverse (in terms of education, income) section of Americans–or in another country. “What is the average person’s concept of nutritious food, too?”

Monsivais said,  “We don’t know that, and it might explain some amount of the variation we found.”

The Centers for Disease Control and Prevention’s NHANES (National Health and Nutrition Examination Survey) could also be tapped to further explore the socio-economic question, he said.

Study results provide fodder for new and different nutrition policy and interventions, which for the last several decades have been mostly premised on the idea that poor diets were due to a lack of nutrition knowledge or insufficient motivation for healthy eating.

“The most universal policy change or intervention would be to rethink how we encourage the production of foods,” said the researchers. “In this country, we have a very expensive agricultural subsidy program that targets a limited range of foods that are not part of a nutritious diet. We do not support fresh produce or seafood, but instead support the production of inexpensive sugars, fat and refined grains. We need to align public health priorities with agricultural policies because it affects the largest number of people.”

In addition, Monsivais said that states could be more creative with public school food programs and other nutrition efforts that affect low-income people. California has experimented with an electronic benefits transfer program (food stamps) that rewards people who buy fresh produce, which makes having a healthier diet easier and more affordable.

Food retailers and grocers could also help consumers make healthier choices, said Monsivais. When you swipe a “member” card at a local store, it could be used in a helpful and healthful way, offering up coupons for items that are nutrient-rich.

“If we could overlay a health lens on top of the member cards and make recommendations that are aligned with the way consumers eat and incentives, we could make it interesting for people,” he said.