Tuesday, July 31, 2012

Toward a More Nuanced Understanding of Food Access


Much of the peer-reviewed literature on food retail access shows that major disparities in the availability of healthy food are based on race and income. The studies generally find that in low-income communities of color, compared to higher wealth or racially mixed neighborhoods, large grocers or supermarkets are sparse or non-existent, the distance to supermarkets is greater, and fresh produce is less available and of lower quality. For a clear and accessible introduction to the issue and a review of the literature, see:




Unfortunately, much of the food access research is limited by being supermarket-centric, ignoring many other types of food retail options, from farmers markets to family-owned green grocers.  Studies have focused on access to large supermarkets for various reasons, often pragmatic: databases of supermarket addresses are more easily accessible compared to information on small produce markets and other food retailers; supermarkets often have a reasonably good assortment of food, enabling researchers to assume that the presence of a supermarket means access to healthy food, avoiding the need to measure food quality directly; and because USDA defines food deserts as places bereft of food retailers that gross more than $2 million in revenue per year, studying supermarket access is more directly relevant to US food access policy.

Apart from the limitations of focusing on supermarkets, studies often use simplified indicators of access that make large-scale studies possible, but fail to reflect how people actually shop. Some measure the distance between the centroid of a geographic area (like a ZIP code, census tract or block) and the nearest supermarket. Many use as-the-crow-flies distances, although others estimate distances based on pathways along streets. Still other studies measure the concentration of food retail outlets within geographic areas.

A subset of food access studies address the dimension of food quality, attempting to measure the type, quantity, variety, and freshness of the food available in grocery stores that are close to particular communities. Inconsistencies in what is counted as a grocery establishment (a chain supermarket or an independent grocer), and the use of consumer evaluations of quality in some studies, make it difficult to compare results and raise questions of reliability.

The relationship between supermarket access to fresh produce and fruit and vegetable consumption is more difficult to measure, given the large number of variables that affect shopping behavior, food purchases, and dietary preferences. Correlating supermarket access and obesity (and diet-related disease) is even more complex, given the large number of variables that contribute to weight gain. Some research shows statistically significant relationships between greater access to healthy foods in close proximity to their home and the consumption of more fresh produce and other healthy food items, though other studies show that the presence of supermarkets does not necessarily make a difference in terms of purchases or consumption of fresh fruits and vegetables, body mass indices, or diet-related disease. Because many studies are based on a snapshot in time, it is difficult to determine the extent to which people with healthier eating habits self-select for neighborhoods with more food availability.

Three recently published studies illustrate the direction we need to move in to develop a more nuanced and policy-relevant understanding of food access. One explores the relationship between the perceived quality of food retail establishments and purchasing decisions, another shows the varied trips that involve food purchases, suggesting that focusing on distance from home to market misses a good percentage of actual shopping activity. The third identifies significant differences between people’s perceived and physical distance to food retailers, illustrating that understanding the dimensions of the food environment that affect our mental models of access may be as or more important in driving shopping and purchasing behavior as physical proximity. All three make the case for incorporating environmental psychology, urban and architectural design, and marketing into the food access debate.

Blitstein, J. L., Snider, J., & Evans, W. D. (2012). Perceptions of the food shopping environment are associated with greater consumption of fruits and vegetables. Public Health Nutrition, 15(06), 1124–1129.

This study confirms that the quality of the shopping environment affects decisions about consuming healthy food. Researchers surveyed a sample of parents of 3-7 year old children in low-income, minority neighborhoods of Chicago, asking them to report their perceptions of their shopping environments, perceived costs of fruits and vegetables, and their food shopping decisions. Those who rated their food shopping environments more positively (based on food quality, selection and convenience) reported consuming fruits and vegetables at a significantly higher rate per day, independent of perceived cost, store type, and the respondent’s social and demographic characteristics. While not entirely unexpected, this research suggests that simply increasing food retail availability without addressing the shopping environment itself, may not improve diets.

Kerr, J., Frank, L., Sallis, J. F., Saelens, B., Glanz, K., & Chapman, J. (2012). Predictors of trips to food desintations. The International Journal of Behavioral Nutrition and Physical Activity, 9(1), 58.

Researchers examined the distances that residents of Atlanta travel to different types of food locations. Not surprisingly for this sprawling city, people travel many miles to visit coffee shops and superstores like Costco, and buy food on the way home from work, on the way to other destinations, as well as during trips that originate from home. Those starting a trip in a neighborhood with few food destinations were less likely to travel to a large grocery store to get food, but those traveling to a “medium accessible” environment (with supermarkets) were more likely to visit a grocery store to purchase food. Because people have such geographically varied patterns for buying food (particularly low-income individuals who spend a significant amount of time away from home for work and other responsibilities), studies focusing on the distance from home to market as a measure of food access miss a large portion of food purchasing activity, and therefore fail to understand where, when, and why people make both healthy and unhealthy food choices. This study indicates the need for research on the availability of food outside of the residential environment, particularly along the “activity spaces” – or travel routes -- of individuals.

Caspi, C. E., Kawachi, I., Subramanian, S. V., Adamkiewicz, G., & Sorensen, G. (2012). The relationship between diet and perceived and objective access to supermarkets among low-income housing residents. Social science & medicine (1982), 75, 1254-1262.

The third study surveyed low-income residents of housing projects in Boston to determine their perception of whether they had a supermarket within walking distance of their homes.  The researchers found that perceived access to a supermarket was significantly related to fruit and vegetable consumption, but that there was a significant difference between perceptions of a supermarket’s proximity and actual distance. One implication of the study is that understanding peoples’ perceptions of distance – which may be related to the quality (aesthetics, safety, familiarity) of the routes to these venues – is as important as the physical distance.

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  3. Some measure the distance between the centroid of a geographic area (like a ZIP code, census tract or block) and the nearest supermarket. Online Pharmacy Many use as-the-crow-flies distances, although others estimate distances based on pathways along streets. Still other studies measure the concentration of food retail outlets within geographic areas.

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