Assessing behaviors associated with fruit and vegetable adequacy

Increased daily intake of fruits and vegetables correlates with a decreased risk for obesity, heart disease, stroke, type 2 diabetes, and certain types of cancer. Given these observations, national and local programs have promoted increased fruit and vegetable consumption. However, most Americans still do not achieve their recommended daily intake of fruits and vegetables.

A need for large scale studies of fruit and vegetable consumption and dietary behaviors. In an effort to understand factors promoting fruit and vegetable intake, various studies have examined demographic and behavioral variables associated with their consumption. Our improved understanding could inform marketing and policy strategies used in social initiatives like the CDC’s “Fruits & Veggies — More Matters” program and the USDA’s Supplemental Nutrition Assistance Program (SNAP).

Several large studies have assessed demographic variables such as age, sex, race, and smoking status associated with fruit and vegetable intake. Other smaller scale studies have examined the relationship between fruit and vegetable intake and particular dietary behaviors, such as dining at fast food restaurants, or dining while watching television. Using insights from these studies, we aimed to broadly assess multiple behaviors associated with fruit and vegetable adequacy while controlling for demographic variables such as age, sex, race/ethnicity, educational attainment, smoking status, and BMI. To do so, we analyzed a large cross-sectional dataset generated from a telephone survey of 4,784 adults living in Indianapolis, Indiana.

Defining fruit and vegetable adequacy in a large scale study. We were particularly interested in creating a more stringent definition of fruit and vegetable adequacy. Due to the high prevalence of obesity, we wanted to avoid simplistic approaches to adequacy, considering that a person consuming a diet replete in sodas and cheeseburgers should not be labeled “adequate” simply for also drinking five glasses of orange juice.

In order to achieve this stringency, we turned to the Healthy Eating Index 2005 (HEI-2005), a tool devised for nutrition composition monitoring and research. The HEI-2005 assigns a numerical score for diet quality relative to the number of calories consumed. For example, a person must eat at least 0.8 cups of vegetables per 1,000 calories to receive the maximum score in the vegetable category. On a 2,500 calorieper-day diet, then, a person must consume two cups of vegetables to achieve the maximum score.

In our analyses, we computed estimated energy requirements for each survey participant using the Harrison-Benedict equation and a multiplier for physical activity. Using these data, self-reported fruit and vegetable consumption quantities, and the HEI-2005 guidelines, we created four independent groups: those receiving the maximum score for both fruits and vegetables (“adequate”), those receiving the maximum score for fruits but not vegetables (“fruit adequate only”), those receiving the maximum score for vegetables but not fruits (“vegetable adequate only”), and those falling short in both categories (“inadequate.”)

Multiple behaviors correlate with increased fruit and vegetable adequacy. Over half of our survey respondents fell within the “inadequate” category, while only about one-tenth met the criteria for adequacy. Controlling for demographic variables, we then assessed various behaviors predicting a respondent’s placement within the “adequate” category versus other categories. Frequent snacking on healthy foods such as fresh fruits, vegetables, or nuts was the single best predictor for placement in the “adequate” category. Other positive predictors included frequent preparation and consumption of meals at home, frequent use of nutritional labels when purchasing food at the market, and the frequent use of symbols such as “heart healthy” icons when ordering food at restaurants. Frequent red meat consumption, by contrast, negatively predicted placement within the “adequate” category.

These results support efforts to promote healthy snacking, such as The Nemours Foundation “Smart Snacking” initiative. Likewise, our data suggest that increased “food awareness” – i.e. the use of labels and symbols – correlates with increased diet quality. In a different aspect, this study demonstrates a novel use for the HEI-2005 in combination with anthropomorphic data, whereby researchers can more precisely assess diet quality in large scale studies. This strategy is not, of course, without limitations, which are further discussed in the original research article found at http://www.cdc.gov/pcd/issues/2011/may/10_0091.htm.