More Availability Does Not Necessarily Increase Consumption

There's been a lot of talk about "food deserts" - those areas, often in low-income neighborhoods, that are marked by a distinct lack of access to fresh foods. Larger grocery stores that offer fresh produce and meats are few and often only accessed by long trips via public transportation. Instead, the produce and fresh foods that are available are overpriced and found in tiny neighborhood markets that don't have the buying power for better prices or the turnover to keep those foods fresh and available. Worse yet, fast food joints are commonplace and within walking distance, making cheap food of questionable nutritional quality more convenient than taking the time to travel to a grocery store, purchase fresh foods and prepare them at home.

It seems quite reasonable, then, that recent health policy has tried to limit the number of fast food restaurants in low-income areas and increase access to supermarkets in the hopes that this will lead to increased consumption of fresh foods.

Does it work?

Researchers from multiple universities around the United States recently collaborated in analyzing data from a study lasting over 15 years and involving over 5,000 young white or black adults living in four major cities of the United States (Arch Intern Med 2011;171(13):1162-1170).

At the start of the study the participants were between 18 and 30 years of age. Initially, and again at years 2, 5, 7, 10 and 15 the participants responded to a dietary questionnaire that measured how frequently they ate at fast food restaurants as well as overall dietary quality, including consumption of fruits and vegetables.

The researchers then matched each participant's home location with the number of fast food restaurants and grocery stores within increasing concentric areas around their home.

Essentially the researchers measured two relationships: number of fast food restaurants in the area related to how often the participants ate fast food, and the number of supermarkets and grocery stores related to their overall diet quality as measured by the amounts of fruits and vegetables they ate.

Surprisingly, they found that for men with the lowest income, a 1% increase in the number of fast food restaurants within 3 kilometers (about 1.8 miles) meant they ate fast food 0.34% more often. Conversely, the number of fast food restaurants in the area was not related to increased fast food consumption in women, regardless of their income.

Again, for men with the lowest income, greater supermarket and grocery store presence within 3 kilometers meant eating slightly more fruits and vegetables, but for high-income women more supermarkets and grocery stores within the same distance meant a lower diet quality.

What this means for you

This poses a difficult question for those in health policy: if more access to healthier foods does not positively influence people's diets, what will? The researchers note many possible influences that may impact people's dietary choices on a level unrelated to the simple number of fast food joints or grocery stores: supermarkets, for example, carry both healthy and unhealthy foods; some fast food restaurants are healthier than others; pricing of healthier foods may be higher in low-income areas as opposed to higher-income areas (due to demand or other factors); and so on. As is so often the case, there does not appear to be a simple solution to a complex problem.

First posted: July 13, 2011