N° 23 | May 2008

Distance to food stores & adolescent male fruit and vegetable consumption: mediation effects

Many children in the USA do not consume five servings of fruit and vegetables per day. Current behavioral models explain a relatively small percentage of the variance in children's fruit and vegetable consumption. Improved understanding of the factors that influence youth fruit and vegetable consumption and how they interact is needed to guide intervention design. A limitation of existing research has been the consideration of psychosocial or environmental influences, separately, on fruit and vegetable consumption. Social cognitive theory suggests that the association between environmental variables and behavior could be either direct or indirect (e.g. a facilitating or buffering effect). An indirect association would suggest that the association is mediated by other variables such as psychosocial variables or home availability of fruits and vegetables. The purpose of this study was to examine associations between distance to food stores and restaurants and fruit and vegetable consumption and the possible mediating role of psychosocial variables and home availability.

Fruit and vegetable consumption of 204 Boy Scouts was assessed by a food frequency questionnaire in 2003. Participant addresses were geo-coded and distance to different types of food stores and restaurants calculated. Fruit and vegetable preferences, home availability and self-efficacy were measured. Regression models were run with backward deletion of non-significant environmental and psychosocial variables. Mediation tests were performed.

Residing further away from a small food store (SFS) (convenience store or drug store) was associated with increased fruit, juice, and low fat vegetable consumption, but proximity to large food stores was not associated with any of the dietary variables. Shopping behavior is considered to be conditional on local supply and the service areas of local grocery stores. If this were true, eating behavior would be a function of distance to a large grocery sto reas people would need to drive further to get to where they do their regular large shopping. We did not find this association in our data, but we did show that fruit and vegetable consumption was inversely associated with access to small stores. Since small stores usually provide a limited supply of fruits and vegetables [46], reduced proximity to these stores may limit consumption of higher calorie foods, which negatively impact fruit, juice, and vegetable consumption. Moreover, among adolescents, who do not drive, it may be that access to small stores is more important than access to the larger grocery stores that require car access (in the city of Houston).

Twenty six percent of the association between distance to the nearest small food store and low fat vegetable consumption was mediated by preferences. Although the data are cross-sectional and therefore the ability to detect a causal association is not possible, the results indicate that participants who lived further away from small grocery stores had increased preferences for fruit and vegetables. Thus, adolescents who have less access to the smaller food stores, which traditionally carry a wider variety of processed foods and less fresh fruit and vegetables, are perhaps more likely to consume fruit and vegetables [at home or in other locations] and develop preferences for them. Moreover, this group of adolescents are perhaps less likely to visit small stores and buy processed foods. Alternatively, it may be the case that families that like fruit and vegetables elect to live in neighborhoods that are further away from small food stores. Further research will need to clarify these relationships.

Residing closer to a fast food restaurant was associated with increased high fat vegetable, fruit, and juice consumption. This seems logical because high fat vegetables such as French Fries are sold at these restaurants. Thus, perhaps adolescents who live close to a fast-food restaurant are more likely to consume the high fat vegetables provided at these stores, a simple facilitating effect. The association with fruit and juice is more difficult to tease out, but it may be that this association is a function of the fruit and juice that these stores sell, or children mistakenly reporting fruit pies or fruit flavored beverages as fruit consumed. Further research will need to clarify this, as well.

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