Evaluating the Healthy Eating Index - 2005

We evaluated the performance of the HEI-2005 by assessing its psychometric properties, including content validity, four types of construct validity, and one type of reliability. To do this, we scored one-day dietary intakes obtained from a sample of 8,650 National Health and Nutrition Examination Survey (NHANES) 2001-2002 respondants. We also scored several sets of exemplary sample menus, including those from the MyPyramid website, the National Heart, Lung, and Blood’s DASH program, Harvard Medical School’s Healthy Eating Pyramid, and the American Heart Association’s No-Fad Diet.

Results of the evaluation showed that the HEI-2005 has both validity and reliability:

• Content validity: All of the key Dietary Guidelines food choice recommendations that relate to diet quality are reflected in HEI-2005 components. By design, the HEI does not cover other Dietary Guidelines recommendations, such as those for physical activity, body weight, and food safety.
• Construct validity: This type of validity evaluates whether an index measures what it is supposed to measure, and the HEI performed well on four types of construct validity. First, four sets of menus representing high-quality diets scored high on the HEI-2005. Second, one-day scores between smokers and non-smokers were significantly different, indicating that the HEI can distinguish between groups with known differences in the quality of their diets. Third, an examination of Pearsons correlations of the HEI-2005 total and component scores with energy intake showed that the HEI can assess diet quality independently of diet quantity. Finally, a principal components analysis (PCA) demonstrated that multiple factors underlie the HEI-2005 and that both the individual components and the total score provide insights into diet quality.
• Reliability: We used Cronbach’s coefficient alpha to assess internal consistency, which is the degree to which multiple components within an index measure the same underlying construct. Results suggest that individual components provide additional insights into the quality of the diet beyond those of the total score.

Additional details are available in the Development and Evaluation of the Healthy Eating Index-2005 Technical Report (PDF).