Despite the prevalence of corner and convenience stores in urban neighborhoods, many residents have to travel farther to find supermarkets that offer a wide variety of healthful food choices, finds a new study in the American Journal of Preventive Medicine.

The study also found that supermarkets in lower income areas and with more people on public assistance had significantly less variety and offered fewer healthier foods.

A 30-block area of West and Southwest Philadelphia was selected for study by the researchers. Residents were 75 percent black, 15 percent white, 6 percent Asian, and 1 percent Hispanic, with 28 percent of households living in poverty, according to the 2010 U.S. Census.

Researchers audited 373 neighborhood stores for the quality and variety of , such as low-fat dairy products, lean meats, and fresh fruits and vegetables; higher scores signified more healthy choices. Nearly 80 percent of food outlets audited were corner or convenience stores that received significantly lower scores.

The researchers also surveyed more than 500 people in the area about their family food shopping. For nearly 90 percent of those surveyed, corner and were the closest places to home to buy food. But only about a third of the people said they bought most of their food at such stores. Respondents reported choosing to shop at a supermarket with a better variety of healthful foods that was an average of more than a mile further than the closest supermarket to their home.

"People rarely said that they did their primary food shopping there. They traveled beyond the closest store," said Carolyn Cannuscio, Sc.D., assistant professor of family medicine and community health at the Perlman School of Medicine at the University of Pennsylvania, Philadelphia, and lead author on the study.

The study's findings shed light on what are called "food deserts," rural or urban areas where there are few or no places to buy fruits, vegetables or healthy foods. "When we think about why lower income people are at higher risk for obesity or disease, we can see there is a difference in the availability of high quality food closer to people's homes." Cannuscio said.

"From a dietician's standpoint, these findings are exciting," said Libby Mills, MS, RDN, LDN, a spokesperson for the Academy of Nutrition and Dietetics and a dietician in private practice in Philadelphia. "This is our overall hope, that when people have access to nutritional food they will choose it."

Both Mills and Cannuscio noted that there have been several efforts in Philadelphia to increase the availability of healthy in the inner city. Several supermarkets, farmers' markets, and co-ops have opened in Philadelphia in the last few years, Mills noted. Public health organizations have also helped corner stores add refrigerated cases that allow them to sell fruits and vegetables, she added. "Philadelphia is now a role model for other major cities."

More information: Cannuscio, C., Tappe, K. and Hillier, A. et al. (2013), Urban food environments and residents' shopping behaviors, Am J Prev Med.

Journal information: American Journal of Preventive Medicine