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A food desert is an area, especially one with low-income residents, that has limited access to affordable and nutritious food. In contrast, an area with supermarkets is termed a food oasis.
By 1973, "desert" was ascribed to suburban areas lacking amenities important for community development. Cummins and Macintyre report that a resident of public housing in western Scotland supposedly invented the more specific term "food desert" in the early 1990s. The phrase was officially used for the first time in a 1995 document from a policy working group of the Low Income Project Team of the UK's Nutrition Task Force.
Initial research was narrowed to the impact of retail migration from the urban center. More recent studies explored the impact of food deserts in other geographic areas (e.g., rural and frontier) and among specific populations, like minorities and the elderly. They address the relationship between the quality (access and availability) of retail food environments, pricing and obesity. The findings support that environmental factors contribute to people's eating behaviors. Research conducted with variations in methods draws a more complete perspective of "multilevel influences of the retail food environment on eating behaviors (and risk of obesity)."
Researchers employ a variety of methods to assess food deserts including: directories and census data, focus groups, food store assessments, food use inventories, geographic information system (GIS) technology, interviews, questionnaires and surveys measuring consumers' food access perceptions. Differences in the definition of a food desert vary according to the:
The multitude of definitions which vary by country have fueled controversy over the existence of food deserts.
Distance-based measurements are used to measure food accessibility and identify food deserts.
The United States Department of Agriculture (USDA) Economic Research Service measures distance by dividing the country into multiple 0.5 km square grids. The distance from the geographic center of each grid to the nearest grocery store gauges food accessibility for the people living in that grid.Health Canada divides areas into buffer zones with people's homes, schools or workplaces as the center. The Euclidean distance, the shortest route distance between the two points of interest, is then measured for gaining food access data.
Different factors are excluded or included that affect the scale of distance. The USDA maintains an online interactive mapping tool for the U.S., the "Food Access Research Atlas," which applies four different measurement standards to identify areas of low food access based on distance from the nearest supermarket.
The first standard uses the original USDA food desert mapping tool "Food Desert Locator" and defines food deserts as having at least 33% or 500 people of a census tract's population in an urban area living 1 mile (10 miles for rural area) from a large grocery store or supermarket.
The second and third standards adjust the scale of distance and consider income to define a food desert. In the U.S., a food desert consists of a low income census tract residing at least 0.5 miles in urban areas (10 miles in rural areas) or 1 mile away in urban areas (20 miles in rural areas) from the large grocery store. The availability of other fresh food sources like community gardens and food banks are not included in mapping and can change the number of communities that should be classified as food deserts. A 2014 geographical survey found that the average distance from a grocery store was 1.76 kilometers (1.09 miles) in Edmonton, but only 1.44 kilometers (0.89 miles) when farmers' markets and community gardens were included, 0.11 miles under the latter definition for an urban food desert.
The fourth standard takes vehicular mobility into account. In the U.S., a food desert exists if 100 households or more with no vehicle access live at least 0.5 miles from the nearest large grocery store; for populations with vehicle access, 500 households or more living at least 20 miles away. Travel duration and mode may be other important factors. As of 2011, public transport is not included in mapping tools.
A food retailer is typically considered to be a healthy food provider if it sells a variety of fresh food, including fruits and vegetables. Types of fresh food retailers include:
Food retailers like fast food restaurants and convenience stores are not typically in this category as they usually offer a limited variety of foods that make up a healthy diet. Frequently too, the produce sold at convenience stores is poor quality. A "healthy" bodega as defined by the New York City Department of Health and Mental Hygiene stocks seven or more varieties of fresh fruits and vegetables and low-fat milk.
Different countries have different dietary models and views on nutrition. These distinct national nutrition guides add to the controversy surrounding the definition of food deserts. Since a food desert is defined as an area with limited access to nutritious foods, a universal identification of them cannot be created without a global consensus on nutrition.
Other criteria include affordability and income level. According to USDA, researchers should "consider... [the] prices of foods faced by individuals and areas" and how "prices affect the shopping and consumption behaviors of consumers." One study maintains that estimates of how many people live in food deserts must include the cost of food in supermarkets that can be reached in relation to their income.
The main difference between a rural and an urban food desert is the distance of residents from the nearest supermarket. Twenty percent of rural areas in the U.S. are classified as food deserts. Within these counties, approximately 2.4 million individuals have low access to a large supermarket. This difference in distance translates into pronounced economic and transportation differences between the rural and urban areas.
A 2009 study of rural food deserts found key differences in overall health, access to food, and social environment of rural residents compared to urban dwellers. Rural residents report overall poorer health and more physical limitations, with 12% rating their health as fair or poor compared to 9% of urban residents. They believed their current health conditions were shaped by their eating behaviors when the future chronic disease risk was affected by the history of dietary intake. Moreover, the 57 recruited rural residents from Minnesota and Iowa in one study perceived that food quality and variety in their area were poor at times. The researchers reached the conclusion that, for a community of people, while food choice which bound by family and household socioeconomic status remained as a personal challenge, social and physical environments played a significant role in stressing and shaping their dietary behaviors.
The primary criterion for a food desert is its proximity to a healthy food market. When such a market is in reach for its residents thereby eliminating the food desert, it does not mean that residents now will eat healthy. A longitudinal study of food deserts in JAMA Internal Medicine shows that supermarket availability is generally unrelated to fruit and vegetable recommendations and over diet quality. The availability of unhealthy foods at supermarkets may impact this relation. Simply providing healthier food access, according to Janne Boone-Heinonen et al., cannot completely eliminate food deserts, this access must be paired with education.
Access to food options is not the only barrier to healthier diets and improved health outcomes. Wrigley et al. collected data before and after a food desert intervention to explore factors affecting supermarket choice and perceptions regarding healthy diet in Leeds, United Kingdom. Pre-tests were administered prior to a new store opening and post-tests were delivered 2 years after the new store had opened. The results showed that nearly half of the food desert residents began shopping at the newly built store, however, only modest improvements in diet were recorded.
A similar pilot study conducted by Cummins et al. focused on a community funded by the Pennsylvania Fresh Food Financing Initiative. They conducted follow up after a grocery store was built in a food desert to assess the impact. They found that "simply building new food retail stores may not be sufficient to promote behavior change related to diet."
A separate survey also found that supermarket and grocery store availability did not generally correlate with diet quality and fresh food intake. Pearson et al. further confirmed that physical access is not the sole determinant of fruit and vegetable consumption. Impediments common with places that are not food deserts remain.
People who have nonstandard work hours that include rotating or evening shifts may have difficulty shopping at stores that close earlier and instead shop at fast food or convenience stores that are generally open later. Under welfare-to-work reforms enacted in 1996, a female adult recipient must log 20 hours a week of "work activity" to receive SNAP benefits. If they live in a food desert and have family responsibilities, working as well may limit time to travel to obtain nutritious foods as well as prepare healthful meals and exercise.
Additional factors may include how different stores welcome different groups of people and nearness to liquor stores. Residents in a 2010 Chicago survey complained that in-store issues like poor upkeep and customer service were also impediments. Safety can also be an issue for those in high crime areas, especially if they have to walk carrying food and maybe also with a child or children.
A possible factor affecting obesity and other "diet-related diseases" is the proximity of fast food restaurants and convenience stores compared to "full-access" grocery stores. Proximity to fast food restaurants correlates with a higher BMI, while proximity to a grocery store correlates with a lower BMI, according to one study.
A 2011 review used fifteen years of data from the Coronary Artery Risk Development in Young Adults (CARDIA) study to examine the fast-food consumption of more than 5,000 young American adults aged 18-30 years in different geographic environments. Fast food chain, supermarket or grocery store availability was treated as a parameter of fast food consumption, diet quality and participants' preferences to fresh fruits and vegetables. The key results of this longitudinal study include:
The research team concluded that "alternative policy options such as targeting specific foods or shifting food costs (subsidization or taxation)" may be complementary and necessary to promote healthy eating habits while increasing the access to large food stores in specific regions and limit the availability of fast food restaurants and small food stores. Some cities already restrict the location of fast food and other food retailers that do not provide healthy food.
Fast food restaurants are disproportionately placed in low-income and minority neighborhoods and are often the closest and cheapest food options. "People living in the poorest SES areas have 2.5 times the exposure to fast-food restaurants as those living in the wealthiest areas".
Other studies have documented a sense of loyalty towards the owners of neighborhood convenience stores as an explanation as to why residents may not change their shopping behaviors.
Steven Cummins also proposed that food availability is not the problem: it is eating habits. Pearson et al. urge food policy to focus on the social and cultural barriers to healthy eating. For instance, New York City's public-private Healthy Bodegas Initiative has aimed to encourage bodegas to carry milk and fresh produce and local residents to purchase and consume them.