UW News

May 7, 2009

Better diets more costly, enjoyed by the most educated

Center for Sensorimotor Neural Engineering

A study conducted at the UW has revealed new connections between food, incomes and education. Researchers found college-educated women had better diets — with more nutrients, vitamins, and minerals — but also paid more for each calorie consumed.

In contrast, study participants with less money, less schooling, and lower diet costs had diets that provided plenty of calories but fewer nutrients. These findings help explain why nutrition related diseases, such as obesity and diabetes, are most common among people with the fewest resources.

“As food prices go up, the natural tendency is to fill up on inexpensive sweets and fats,” said Adam Drewnowski, director of the UW Center for Public Health Nutrition. “We need to make affordable nutrient-rich foods available to every American household.” Results from the study are published in the May 2009 issue of the Journal of the American Dietetic Association.

Researchers Drewnowski and Pablo Monsivais, a CPHN investigator, examined eating habits, diet quality, and estimated diet costs of 164 adult volunteers in the Seattle area. Study participants had above-average education and incomes. Male and female participants recorded their usual frequency of consumption of 152 foods and 22 beverages, and indicated portion sizes. They also completed demographic and behavioral questionnaires. Food prices, obtained from three major Seattle-area supermarket chains and adjusted for preparation and waste, were used to estimate the daily cost ($/day) of each person’s diet.

Higher-quality diets were defined as those that provided relatively more nutrients than calories. By contrast, lower-quality diets were those that provided more calories and fewer nutrients per gram. Previous studies had described such diets as being energy rich but nutrient poor. In their study, Monsivais and Drewnowski found that higher dietary energy density was associated with more total fat and saturated fat and with less dietary fiber, potassium and vitamins A and C. As in past studies, energy dense diets provided the most empty calories for the least money.

Overall, the healthiest diets were enjoyed by those participants who had the most education and the highest incomes. A closer look at the diets of men and women showed that women had higher-quality diets than did men, and that women’s diet quality improved sharply for every additional dollar spent.

On the flip side, higher food spending among men did not always lead to diets that were lower in fat or saturated fat. The researchers speculate that women wishing to improve diet quality select fresh vegetables and fruit, whereas men may be happy with steak.

Current research on affordable nutrition shows that the links between diet quality and diet cost may hold across all strata of American society. A recent study conducted by Marilyn Townsend from the University of California-Davis, in collaboration with Monsivais and Drewnowski, among low-income women who were recipients of food assistance found that healthier diets were also more costly.

Low-income women in that study were even more likely to scale back on food costs, cutting things from their diets like fresh fruit and vegetables, and relying on sweetened beverages instead. As costs increased, dietary energy density (calories), total energy, fat and sugar intakes decreased, while vitamin A intake (nutrition) increased. Results from the study were published in the April 2009 issue of the American Journal of Clinical Nutrition (and released online in February 2009).

“We’ve known for decades that there were differences in diet quality between the rich and the poor” said Monsivais. “When it comes to food, you get what you pay for.”

Monsivais and Drewnowski said that affordable healthy diets can be within reach of the average consumer regardless of income. What the public needs is better dietary guidance about affordable nutrient-rich foods within each food group, they said. “Rather than promote high-cost foods to low-income people, let’s focus on what appealing, affordable, popular foods are out there,” said Drewnowski. “But let’s not pretend that all Americans have an infinite variety of food choices before them, because some groups of our society clearly do not.”

UW researchers note that studies of nutrition and food price have implications for the food assistance and education programs of the U.S. Department of Agriculture (USDA). Drewnowski recently testified on this topic in Washington, D.C., for the 2010 Dietary Guidelines Advisory Committee, which is charged by Congress with improving the quality of the American diet. The USDA funded both the Seattle and California studies through the National Research Initiative Human Nutrition and Obesity Program.