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Article Excerpt
Since the first edition of the Dietary Guidelines for Americans in 1980, the U.S. Department of Agriculture (USDA) and the U.S. Department of Health and Human Services (DHHS) have recommended eating a variety of foods to ensure individuals consume all essential nutrients for both general health and chronic disease prevention (USDA & DHHS, 1980; USDA & DHHS, 1985; USDA & DHHS, 1990; USDA & DHHS, 1995; USDA & DHHS, 2000). Over the course of the five editions, guidance has evolved: "eat a variety of foods" (1980, 1985, 1990, 1995), "choose a variety of grains daily, especially whole grains" (2000), and "choose a variety of fruits and vegetables daily" (2000). The five food groups consist of grains, vegetables, fruits, milk and milk products, and meat and beans. No single food or food group supplies adults and children 2 years and older with all the essential nutrients and other important food substances in the amounts needed for good health. Analysis of data from the first National Health and Nutrition Examination Survey (NHANES I) Epidemiologic Follow-up Study demonstrated that those who consume foods from only one or two food groups had a significantly higher risk of all-cause mortality. This was the case even after other major risk factors such as race, education, smoking, and dietary fiber consumption were controlled (Kant, Schatzkin, Harris, Ziegler, & Block, 1993).
Whole grains, fruits, and vegetables contain concentrated amounts of vitamins, minerals, antioxidants, dietary fiber, phytochemicals, and other substances that may protect against several chronic diseases. For example, increased consumption of good sources of dietary fibers--such as grains, fruits, vegetables, and beans--can lower blood cholesterol levels; help to regulate blood sugar; and lower the risks of cardiovascular disease, diabetes, and colon cancer (Marlett, McBurney, & Slavin, 2002). Similarly, regular consumption of whole grains has been associated with a reduction in cardiovascular disease, diabetes, cancer mortality, and premature death (Lang & Jebb, 2003).
A recent research review illustrated that while there are thousands of beneficial plant substances, no single plant substance alone provides the protective effects from chronic diseases. Also, when these plant substances are taken as supplements rather than consumed as they naturally occur in plant products, their protective effects are minimal (Buttriss, 2004). Therefore, the basis for recommending a variety of whole grains, fruits, and vegetables is well founded.
Within the nutrition field, the definition of variety is inconsistent; and misinterpretation of the term can potentially lead to confusion or unintended consequences. Focus group research on the 2000 Dietary Guidelines found that consumers interpreted eating a "variety" to mean that one should eat foods from all food groups, which may lead to eating a variety of foods high in fat and added sugars (Prospect Associates, 1998).
Methods used to measure variety also matter in examining the link between food consumption and health outcomes. Researchers have used at least three different methodologies to measure variety: (1) count the number of unique foods (1) (used in our methodology) (Bernstein et al., 2002; Krebs-Smith, Smiciklas-Wright, Guthrie, & Krebs-Smith, 1987); (2) count the number of foods from each Pyramid food group (Kant et al., 1993; Kim, Haines, Siega-Riz, & Popkin, 2003); and (3) divide foods as consumed into groups (Drewnowski, Henderson, Driscoll, & Rolls, 1997; Haines, Siega-Riz, & Popkin, 1999; McCrory et al., 1999; Wirfalt & Jeffery, 1997). For example, the first two methods would classify a vegetable stir-fry by the unique foods it contains (e.g., onions, carrots, and string beans); the third method would classify this mixed dish as a "vegetable stir-fry."
In 1995, the USDA Center for Nutrition Policy and Promotion (CNPP) constructed the Healthy Eating Index (HEI) to measure individuals'...
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