approach can capture these multiple dimensions. The most commonly used summary measure of diet quality is the HEI-2005, and improvement in HEI scores among both the general population and low-income groups is a performance measure for the goal of “improving the nation’s nutrition and health” in USDA’s Strategic Plan for 2005-2010.
HEI-2005 scores show that most Americans, including SNAP participants and other low-income groups, are falling short of meeting the current DGA. This failure among Americans at all income levels highlights that the HEI-2005 (or other measures of diet quality) should not be used as a sole measure of the adequacy of SNAP allotments. SNAP participants—and other Americans—may have reasons for choosing foods with low nutrient density, and limited household resources for obtaining food is just one of these reasons. A related challenge to assessing access to a healthy diet is entailed in measuring diet quality. A number of methodologies are used to collect data on dietary intake. Interviewer-administered 24-hour dietary recalls are appropriate for a less educated population for monitoring and surveillance purposes. This method decreases respondent burden and greatly improves data quality compared with other methods; however, it is expensive, and a protocol using multiple 24-hour recalls is challenging to complete.
A limited number of datasets include dietary intake at the individual level. Most national-level datasets cannot be used to assess individual-level diet quality because this type of data cannot be aggregated by income level or program participation. Given these limitations, NHANES is currently the best dataset available for examining diet quality in low-income, including SNAP, populations because it is based on state-of-the-art data collection on dietary intake, includes the full 18-item Core Food Security Module, and includes information on SNAP participation. Nevertheless, NHANES is only one dataset, and although it examines a nationally representative sample, only about 5,000 persons located in 15 counties across the country are sampled each year. Furthermore, inherent challenges arise in identifying whether respondents within the same household are related and with linking individuals to external data sources. In addition, NHANES measures SNAP participation through self-report and includes substantial measurement error. Linking the NHANES data to another administrative data source with more accurate reporting of SNAP participation might improve understanding of the association between SNAP participation and dietary intake. Another limitation of NHANES is that, because it is cross-sectional, it does not permit tracking changes in food security or access to a healthy diet over time.
More research is needed to test the validity of the HEI as a comprehensive measure that captures overall diet quality, whether it is internally reliable and therefore highly correlated with other important components of