The Healthy Eating Index (HEI) has been evaluated by assessing its psychometric properties, including content validity, four types of construct validity, and one type of reliability. Since 2005, analyses have been conducted to evaluate the HEI’s psychometric performance.
To do this, we scored dietary data from the most recent National Health and Nutrition Examination Survey (NHANES) for each version of the HEI. Data from 2001-2002 NHANES were used to evaluate HEI-2005; data from NHANES 2003-2004 were used to evaluate HEI-2010; and data from NHANES 2011-2012 were used to evaluate HEI-2015.
We also scored several sets of exemplary sample menus. For the HEI for ages 2 and older, this has included the United States Department of Agriculture's (USDA) website, the National Heart, Lung, and Blood Institute's (NHLBI) DASH program, Harvard Medical School's Healthy Eating Pyramid, and the American Heart Association's No-Fad Diet.
Results of the evaluations showed that the HEI has both validity and reliability:
- Content validity: For HEI-2005, HEI-2010 and HEI-2015, all of the key food choice recommendations of the Dietary Guidelines that relate to diet quality are reflected in HEI 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 fairly high on the HEI–2005, HEI-2010 and HEI-2015. Predictably, as the HEI was refined over time, some menus scored lower on later versions of the HEI, reflecting the refinement of advice on subgroups such as dark green vegetables and components such as added sugar.
- Second, one-day scores between smokers and non-smokers were significantly different in all versions, indicating that the HEI can distinguish between groups with known differences in the quality of their diets.
- Third, an examination of Pearson's correlations of the HEI 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 each version of the HEI and that both the individual components and the total score provide insights into diet quality. A new addition to the evaluation of construct validity in 2010 came with a new statistical method known as the Markov Chain Monte Carlo (MCMC) method, which allowed us to estimate distributions of HEI scores of estimated usual intake in the population (rather than only the mean scores) to assess whether the distribution was wide enough to detect meaningful differences.
Reliability: For all versions, 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.
For additional details:
- Reedy J, Lerman JL, Krebs-Smith SM, Kirkpatrick SI, Pannucci TE, Wilson MM, Subar AF, Kahle LL, and Tooze JA. Evaluation of the Healthy Eating Index-2015. J Acad Nutr Diet. 2018 Sep;118(9):1622-1633.
- Guenther PM, Kirkpatrick SI, Reedy J, Krebs-Smith SM, Buckman DW, Dodd KW, Casavale KO, Carroll RJ. The Healthy Eating Index-2010 is a valid measure of diet quality according to the 2010 Dietary Guidelines for Americans. J Nutr. 2014 Mar;144 (3):399-407.
- Guenther PM, Reedy J, Krebs-Smith SM, Reeve BB. Evaluation of the Healthy Eating Index–2005. J Am Diet Assoc. 2008 Nov;108(11):1854-64.