© 2002 American Public Health Association
At the time of the study, Kimberly Morland was, and Steve Wing is, with the Department of Epidemiology, University of North Carolina, Chapel Hill. Ana Diez Roux is with the Division of General Medicine, College of Physicians and Surgeons and the Department of Epidemiology, Mailman School of Public Health, Columbia University, New York, NY. Correspondence: Requests for reprints should be sent to Kimberly Morland, PhD, Department of Community and Preventive Medicine, Mount Sinai School of Medicine, 1 Gustave L. Levy Place, Box 1057, New York, NY 10029 (e-mail: kimberly.morland{at}mssm.edu).
Objectives. We studied the association between the local food environment and residents report of recommended dietary intake. Methods. Recommended intakes of foods and nutrients for 10 623 Atherosclerosis Risk in Communities participants were estimated from food frequency questionnaires. Supermarkets, grocery stores, and full-service and fast-food restaurants were geocoded to census tracts. Results. Black Americans fruit and vegetable intake increased by 32% for each additional supermarket in the census tract (relative risk [RR] = 1.32; 95% confidence interval [CI] = 1.08, 1.60). White Americans fruit and vegetable intake increased by 11% with the presence of 1 or more supermarket (RR = 1.11; 95% CI = 0.93, 1.32). Conclusions. These findings suggest the local food environment is associated with residents recommended diets.
The relationship between diet and disease is well established. Research linking dietary intake to cancer,14 diabetes,5 hypertension,6,7 birth defects,8,9 and heart disease4,1012 has led to dietary change recommendations. For instance, in 1961, the American Heart Association recommended a reduction in total fat, saturated fat, and cholesterol and an increase in polyunsaturated fats for Americans diets.13 Currently, the American Cancer Society, the American Dietetic Association, the American Academy of Pediatrics, the National Institutes of Health, and the American Heart Association recommend a healthy eating program based on the Department of Agricultures Food Guide Pyramid.14,15 Although recommendations for dietary modifications have spanned more than 4 decades, many intervention trials have had difficulty producing sustainable dietary changes.1618 Researchers have found that dietary choices are influenced by a variety of factors, including knowledge of the causative and preventive effects of certain foods, the cost of food, and the availability of different foods. For instance, the change in US regulatory policy in 1985, allowing producers to advertise the relationship between food products and health, has led to improvements in food choices for some individuals.19,20 Similarly, researchers have found that improving knowledge of the relationship between diet and health influences food choices.21,22 In addition to specific knowledge of the relationship between diet and health, educational attainment is associated with dietary choices.23,24 As well as knowledge, the affordability of food has been documented as a factor influencing peoples diets. For instance, research suggests that even when receiving combined aid from Food Stamps, Aid to Families with Dependent Children, and Supplemental Security Income, some people have not been able to meet their nutritional needs.25 These authors speculate that the migration of supermarkets to the suburbs and a lack of transportation contribute to the malnutrition experienced by low-income Americans. In addition, foods recommended by health authorities are sometimes more expensive and less available in poor areas2629 and, although people with low incomes spend less money, a greater proportion of their income is spent on food.30,31 Furthermore, current research shows a lower prevalence of supermarkets and a higher prevalence of independently owned grocery stores in low-wealth and predominately Black neighborhoods and a greater proportion of households without access to private transportation in these neighborhoods.32 The impact that the availability of healthy foods has on peoples diets has received somewhat less attention. Alcohol research suggests that alcoholic beverage consumption increases with an increase in the availability of alcohol3335; however, fewer studies have researched whether the availability of recommended foods affects their consumption.36 This study measured the association between the physical availability of food stores and food service places and peoples adherence to health authorities recommendations for a healthy diet. The following 4 indicators of a "healthy diet" have been selected because of their causative or preventive relationship with disease and consistent recommendations from health authorities: (1) servings of fruits and vegetables per day, (2) percentage of calories from fat, (3) saturated fat, and (4) dietary cholesterol. The Atherosclerosis Risk in Communities (ARIC) study has been selected for this analysis because (a) these data have already been collected for a large population-based sample with extensive information on dietary intake, (b) the geographic area from which the ARIC population was sampled is diverse with respect to the wealth and racial makeup of residential census tracts, (c) the ARIC participants are heterogeneous in terms of race, income, and education (all characteristics known to be associated with dietary intake), and (d) neighborhood differences in diet have been found for these community members.37 There are both clinical and public health benefits to understanding how the local environment may influence food choices. From a clinical perspective, it is important to know whether the dietary guidelines being prescribed are actually achievable. Clinicians may need to take into account the local food environment when prescribing dietary modifications. The benefit to public health is the opportunity to intervene at an environmental level, while still educating people about the relationship between diet and disease. The difficulty in changing dietary behavior may stem from the environmental factors that either reduce peoples motivation to adopt a healthy diet or make changes difficult or impossible to achieve. These limitations may stem from the characteristics of ones local food environment.
The Local Food Environment 1990 census tracts were used as approximations of neighborhoods, and the local food environment was characterized by the number and types of food stores and food service places located in the census tract where a participant lived.38 Of the 221 census tracts used, 29 were located in Washington County, Maryland, 80 in Forsyth County, North Carolina, 58 in Jackson City, Mississippi, and 54 in the following suburbs of Minneapolis, Minnesota: Brooklyn Center, Brooklyn Park, Crystal, Golden Valley, New Hope, Plymouth, and Robbinsdale. Five tracts were excluded because they contained 10 or fewer housing units and 8 because they had no ARIC participants or because ARIC participants were excluded, leaving 208 tracts available for analysis (Maryland = 28, North Carolina = 78, Mississippi = 48, Minnesota = 54). Names and addresses of food stores and food service places for each of the 4 communities were collected in 1999 from the local health departments and state departments of agriculture. A commercial firm carried out the geocoding using 2 methods. Seventy-five percent of business addresses were linked to census tracts by exact address matching, and the remainder was estimated from zip code centroids.39 Food stores and food service places were assigned an industry code based on the 1997 North America Industry Classification System (NAICS). Food stores are defined as industries that retail food and beverage merchandise from fixed point-of-sale locations, including supermarkets, grocery stores, convenience stores, and specialty food stores. Supermarkets have a larger selection of healthy food40 at lower prices41; therefore, these large corporate-owned "chain" stores are distinguished from small locally owned grocery stores. Food service places are defined as industries that prepare meals, snacks, and beverages by customer order for immediate on-premises and off-premises consumption; they include full-service restaurants, limited-service eating places, and bars and taverns. Limited-service eating places include franchised fast-food restaurants and other restaurants serving over-the-counter meals and snacks. A full description of the NAICS codes and methods for assigning these codes has been described elsewhere.32,42 Supermarkets and grocery stores sell 92% of the volume of annual sales of all food and beverage stores in the United States.43 Furthermore, full-service and limited-service restaurants sell 82% of the volume of sales of all food service and drinking places.44 Therefore, food stores and food service places other than supermarkets, grocery stores, full-service restaurants, and fast-food restaurants were investigated only as covariates, since their contributions to peoples local food environments are negligible.
ARIC Participants
Dietary Intake A healthy diet was defined for individuals as one meeting the US Department of Agriculture and the US Department of Health and Human Services Dietary Guidelines for Americans: (a) at least 2 servings of fruit and at least 3 servings of vegetables per day, (b) 30% or less of calories from total fat, (c) less than 10% of calories from saturated fat, and (d) 300 or fewer milligrams of dietary cholesterol per day.15,47,48
Statistical Methods Models were stratified by race, and 2 series of adjusted models were then calculated for each racial group. The first adjusted model included terms for all types of food stores and food service places to reflect the fact that peoples local food environments are composed of a variety of food stores and restaurants. Because education and income are associated with both diet and where people live, the second adjusted model included education and income in addition to food stores and food service places. Food stores and food service places were dichotomized as any vs none of a particular kind, and people with 12 years of education or more were compared with people with less than 12 years of education. Annual family income was categorized as follows: less than $5000, $5000 to $7999, $8000 to $11 999, $12 000 to $15 999, $16 000 to 24 999, $25 000 to $34 999, $35 000 to 39 999, and $40 000 to $49 999; people in these categories were compared with people with incomes of $50 000 or more. Age had very little influence on the association between the local food environment and residents reported diets; therefore, adjustment for age was not made. Finally because recommended intake of these foods and nutrients are made independent of caloric intake, adjustment for calories was not made in any of the analyses.
Demographic and dietary characteristics of the Black and White participants are presented in Table 1
Reported dietary intake of total fat and saturated fat were similar for Black and White Americans, but fruit, vegetable, and cholesterol intake was higher for Black Americans. The proportion of Americans that ate at least 2 fruits and at least 3 vegetables per day was low, although more Black Americans reported meeting this dietary recommendation. In addition, more Black Americans met the recommendations for saturated fat. Conversely, more White Americans met recommendations for cholesterol. There were fewer supermarkets than any of the other types of food establishment for both groups; however, 5 times more supermarkets were located in census tracts where White Americans resided. Neighborhoods where White Americans resided contained more full-service restaurants but fewer grocery stores. Fast-food restaurants were fairly evenly dispersed across neighborhoods.
Black Americans
The proportion of meeting dietary recommendations for total fat was about 25% higher among Black Americans living in a census tract with at least one supermarket (RR = 1.27; 95% CI = 1.09, 1.49), with a 4% change after adjustments (Table 2
Although 73% of Black Americans lived in areas with a small grocery store, their presence showed little association with the reported diets of Black Americans. Parameter estimates of the association between grocery stores and healthy eating were close to the null and confidence intervals were narrow. Adjustments affected the relative risks and confidence intervals very little (Table 2 Most Black Americans (79%) lived in areas with full-service restaurants. The presence of this type of food service place was more strongly associated with residents intake of saturated fat than with other recommendations. Compared with Black respondents living in areas without full-service restaurants, those living in neighborhoods with at least one full-service restaurant reported a 26% increase in meeting the recommended diet for saturated fat, which was largely unaffected by additional adjustments (RR = 1.26; 95% CI = 0.95, 1.27).
Nearly 60% of Black respondents lived in neighborhoods with at least one fast-food restaurant; however, small parameter estimates and narrow confidence intervals indicated that there was little association between the presence of fast-food restaurants and reported dietary intake of recommended foods and nutrients (Table 2
White Americans
Results of this study show some associations between the local food environment and residents reports of meeting dietary recommendations. Black Americans living in areas with supermarkets have healthier diets in terms of fruits and vegetables, total fat, and saturated fat. We also observed that Black Americans living in neighborhoods with full-service restaurants had healthier diets in terms of saturated fat. These observations were less pronounced for White Americans. Although the risk ratios for supermarkets are in the same direction for the same indicators of healthy eating, the magnitudes of effects were not as great. Adjustment for other covariates resulted in very little change (< 10%) in the magnitude of the effects or the width of the confidence intervals. Once other food stores were controlled for, point estimates and confidence intervals changed little with control for socioeconomic variables that represent mechanisms thought to be associated with healthy eating, such as individuals educational attainment2124 and the ability to afford healthy foods.2531 In addition to socioeconomic factors, by design Black Americans were sampled primarily from North Carolina and Mississippi, whereas White Americans were sampled from Minnesota, Maryland, and North Carolina. Therefore, the associations observed between the local food environment and dietary intake may be specific to the geographic areas studied and results for Black and White Americans may not be comparable. However, when analyses were restricted to North Carolina, where both Black and White Americans were sampled, we still observed an increase in meeting recommendations for fruit and vegetable intake for Black Americans (RR = 1.65; 95% CI = 1.00, 2.71) but a decrease for White Americans (RR = 0.89, 95% CI = 0.70, 1.15). This interaction between race and the local food environment suggests there may be other race-specific mechanisms involved in the relationship between the local food environment and dietary intake. For example, White Americans living in the areas under study had 3 times greater access to private transportation than Black Americans living in similar locations, so that White Americans had a larger geographic area in which to select places to patronize.32 Therefore, White Americans may be less reliant than Black Americans on their immediate neighborhood for food. This issue of transportation is one of many that make defining the local food environment for individuals difficult. Although research has shown that census tracts are good approximations for neighborhoods, without information on peoples shopping habits there is no validation that people actually purchase food within their tract.38 This may be more of an issue for individuals living on the boarder of 2 tracts, people who work outside of their home, or people with access to transportation. In addition, although commercial geocoding is an efficient and costeffective strategy for linking addresses to census tracts, addresses could have been misclassified with respect to neighborhood and residential characteristics, in which case our estimates may be biased. Using the number and type of stores as a proxy for the availability of healthy foods was also a limitation. We assumed that supermarkets offer the widest selection of foods at the lowest prices. However, these analyses may be improved with more specific information regarding the types and costs of foods sold at these establishments. Moreover, because the dietary data were collected before the local food environment data, we had to assume that the proportion of the various types of food stores and restaurants remained constant between 1993 and 1999. Finally, there are other factors that influence peoples dietary choices that we were unable to control for; these may also be associated with the local food environment. Although future studies may offer more information on pathways by which the local food environment is associated with dietary intake, these data show that the local food environment is associated with meeting dietary recommendations for some individuals. These findings are most pronounced for supermarkets, which generally offer a larger selection of foods at lower prices. Local food environments may become more equitable with changes in policy and resources that support a wider variety of healthy foods at lower prices in neighborhood grocery stores and encouragement of supermarkets to locate in low-income and Black neighborhoods.
K. Morlands work was funded by the University of North Carolinas School of Medicine Womens Health Research Grant. S. Wing was supported in part by National Institute of Environmental Health Sciences grant 2 R25 ES0820605 under the "Environmental Justice: Partnerships for Communication" program, and A. Diez Roux was supported by National Heart, Lung, and Blood Institute grant R29 HL59386. We would also like to thank Drs Lori CarterEdwards, Gerardo Heiss, Nancy Milio, Charles Poole, Paul Sorlie, and Hermann A. Tyroler and Corrine Munoz-Plaza for their useful comments.
Human Participant Protection
K. Morland was responsible for conceptualizing the study, obtaining the local food environment data, performing the data analysis, and preparing the manuscript for publication. S. Wing provided advice regarding methods and analysis. A. Diez Roux provided statistical advice and funded the geocoding. S. Wing and A. Diez Roux also contributed to writing and editing the manuscript. Accepted for publication November 26, 2001.
1. Willet WC, Trichopoulos D. Nutrition and cancer: a summary of the evidence. Cancer Causes Control. 1996;7:178180.[Medline] 2. Block G, Patterson B, Subar A. Fruit, vegetables and cancer prevention: a review of the epidemiological evidence. Nutr Cancer. 1992;18:129.[Medline] 3. Levi F, Pasche C, La Vecchia C, Lucchini F, Franceschi S. Food groups and colorectal cancer risk. Br J Cancer. 1999;79:12831287.[Medline] 4. Hercberg S, Galan P, Preziosi P, Alfarez M, Vazquez C. The potential role of antioxidant vitamins in preventing cardiovascular diseases and cancers. Nutrition. 1998;14:513520.[Medline]
5. Swinburn BA, Metcalf PA, Ley SJ. Long-term (5-year) effects of a reduced-fat diet intervention in individuals with glucose intolerance. Diabetes Care. 2001;24:619624.
6. Taubes G. New study says low-fat diet can lower blood pressure. Science. 1997;276:350. 7. Jones WO, Brown J. The relationship of diet to blood pressure control. J Natl Med Assoc. 1979;71:11461148.[Medline] 8. Shaw GM, Schaffer D, Velie EM, Morland KB, Harris JA. Periconceptional vitamin use, dietary folate, and the occurrence of neural tube defects. Epidemiology. 1995;6:219226.[Medline]
9. Botto LD, Mulinare J, Erickson JD. Occurrence of congenital heart defects in relation to maternal multivitamin use. Am J Epidemiol. 2000;151:878884. 10. Hjermann I. A randomized primary prevention trial in coronary heart disease: The Oslo Study. Prev Med. 1983;12:181184.[Medline] 11. Rexrode KM, Manson JE. Antioxidants and coronary heart disease: observational studies. J Cardiovasc Risk. 1996;3:363367.[Medline] 12. Yen PK. Stopping heart disease with diet. Geriatr Nurs. 1998;19:5051.[Medline]
13. Page IH, Allen EB, Chamberlain FL, Keys A, Stamler J, Stare FJ. Dietary fat and its relation to heart attacks and strokes. Circulation. 1961;23:133136. 14. CNN staff, health gurus agree on one diet to fight disease [transcript]. CNN. June 16, 1999. 15. Nutrition and Your Health: Dietary Guidelines for Americans. 5th ed. Washington, DC: US Dept of Agriculture; 2000. Home and Garden Bulletin No. 232.
16. Farquhar JW, Fortmann SP, Flora JA, et al. Effects of communitywide education on cardiovascular disease risk factors: the Stanford Five-City Project. JAMA. 1990;264:359365.
17. Carleton RA, Lasater TM, Assaf AR, Feldman HA, McKinlay S. The Pawtucket Heart Health Program: community changes in cardiovascular risk factors and projected disease risk. Am J Public Health. 1995;85:777785.
18. Luepker RV, Rastam L, Hannan PJ, et al. Community education for cardiovascular disease prevention: morbidity and mortality results from the Minnesota Heart Health Program. Am J Epidemiol. 1996;144:351362. 19. Ippolito PM, Mathios AD. Nutrition information and policy: a study of the US food production trends. J Consumer Policy. 1994;17:271305. 20. Lang JE, Mercer N, Tran D, Mosca L. Use of a supermarket shelf-labeling program to educate a predominately minority community about foods that promote heart health. J Am Diet Assoc. 2000;7:804809.
21. Campbell MK, Denmark-Wahnefried W, Symons M, et al. Fruit and vegetable consumption and prevention of cancer: the black churches united for better health project. Am J Public Health. 1999;89:13901396. 22. Carlson KA, Gould BW. The role of health knowledge in determining dietary fat intake. Rev Agriculture Econ. 1994;16:373385. 23. Shimakawa T, Sorlie P, Carpenter MA, et al. Dietary intake patterns and sociodemographic factors in the Atherosclerosis Risk in Communities study. Prev Med. 1994;23:769780.[Medline]
24. Shea S, Stein AD, Basch CE, et al. Independent associations of education attainment and ethnicity with behavioral risk factors and cardiovascular disease. Am J Epidemiol. 1991;134:567582. 25. Urban Grocery Gap. Washington, DC: US House of Representatives Select Committee on Hunger; 1992:2021. 26. Mooney C. Cost and availability of healthy food choices in a London health district. J Hum Nutr Diet. 1990;3:111120. 27. Sooman A, Macintyre S, Anderson A. Scotlands healtha more difficult challenge for some? The price and availability of healthy foods in socially contrasting localities in the west of Scotland. Health Bull. 1993;51:276284. 28. Lawn J, Robbins H, Hill F. Food affordability in air stage communities. Int J Circumpolar Health. 1998;57(suppl 1):8288.[Medline] 29. Cade J, Upmeier H, Calvert C, Greenwood D. Cost of a healthy diet: analysis from the UK Womens Cohort study. Public Health Nutr. 1999;2:505512.[Medline] 30. Lang T. Food policy and public health. Public Health. 1992;106:91125.[Medline] 31. Obtaining Food: Shopping Constraints on the Poor. Washington, DC: US House of Representatives Select Committee on Hunger; 1987. 32. Morland K, Wing S, Diez Roux A, Poole C. Neighborhood characteristics associated with the location of food stores and food service places. Am J Prev Med. 2002;22:2329.[Medline] 33. Adrian M, Ferguson BS, Her M. Does allowing the sale of wine in Quebec grocery stores increase consumption? J Stud Alcohol. 1996;57:434448.[Medline] 34. Wagenaar AC, Langley JD. Alcohol licensing system changes and alcohol consumption: introduction of wine into New Zealand grocery stores. Addiction. 1995;90:773783.[Medline] 35. Gruenewald PJ, Ponicki WR, Holder HD. The relationship of outlet densities to alcohol consumption: a time series cross-sectional analysis. Alcohol Clin Exp Res. 1993;17:3847.[Medline]
36. Wechsler H, Basch CE, Zybert P, Lantigua R, Shea S. The availability of low-fat milk in an inner-city Latino community: implications for nutrition education. Am J Public Health. 1995;85:16901692. 37. Diez-Roux AV, Nieto FJ, Caulfield L, Tyroler HA, Watson RL, Szklo M. Neighborhood differences in diet: the Atherosclerosis Risk in Communities study. J Epidemiol Community Health. 1999;53:5563.[Abstract] 38. White MJ. American Neighborhoods and Residential Differentiation. New York, NY: Russell Sage; 1987:1820. 39. Geographic data technology. Available at: http://www.geographic.com/home/index.cfm. Accessed November 1999. 40. Salis JF, Nader R, Atkins J. San Diego surveyed for heart healthy foods and exercise facilities. Public Health Rep. 1986;101:216218.[Medline] 41. Curtis KA, McClellan S. Falling through the safety net: poverty, food assistance and shopping constraints in an American city. Urban Anthropol. 1995;24:93135. 42. Economic Classification Policy Committee. NAICS: New Data for a New Economy. Washington, DC: US Bureau of the Census; 1998. 43. 1997 United States Economic Census: Retail Trade. Washington, DC: US Bureau of the Census; 2000. 44. 1997 United States Economic Census: Accommodation and Foodservices. Washington, DC: US Bureau of the Census; 2000.
45. ARIC Investigators. The Atherosclerosis Risk in Communities (ARIC) study: design and objectives. Am J Epidemiol. 1989;129:687702. 46. Consumer and Food Economics Institute. Composition of Foods. Washington, DC. US Dept of Agriculture; 1975/89. Agriculture Handbook No. 8 series.
47. Dixon LB, Cronin FJ, Krebs-Smith SM. Let the pyramid guide your food choices: capturing the total diet concept. J Nutr. 2001;131(2S-1):461S472S.
48. Dixon LB, Ernst ND. Choose a diet that is low in saturated fat and cholesterol and moderate in total fat: subtle changes to a familiar message. J Nutr. 2001;131(2S-1):510S526S. 49. Littell RC, Milliken GA, Stroup WW, Wolfinger RD. SAS System for Mixed Models. Cary, NC: SAS Institute Inc; 1996. This article has been cited by other articles:
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