Neighbourhood socioeconomic characteristics are associated with differences in food intake after adjusting for individual characteristics.¹ Neighbourhood-level characteristics could contribute to ethnic and economic differences in dietary patterns. Systematic measurement of environmental variables is a challenge in epidemiology.²

In Baltimore, we are studying the effect of availability and price of food on cardiovascular risk by visiting 366 food stores in neighbourhoods of 1000 participants in a cardiovascular study.³

Within 1 mile of the grocery store (fig 1) reside 83 of the study participants. This store offers money orders, alcohol and lottery tickets, but no fruits or vegetables, no wholewheat bread and no skimed milk. The price of milk, cereal and bread was 20% higher than that in the closest supermarket 1.7 miles away. This store is not an exception.

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Figure 1

 Grocery store in Baltimore City, USA.

A poor diet resulting in obesity is a major factor in the epidemic of non-communicable diseases, which disproportionately affects the poor.⁴ Epidemiologists need to deal with this problem, if recommended diets based on fruits and vegetables, wholewheat bread, and low-fat dairy products are to be made available and affordable to both the high-risk and general populations.⁵