A diet quality index (DQI) provides a summary measure of overall diet quality. It represents a collection of scores applied to selected dietary components deemed to be representative of a healthy diet. Internationally, measures of overall diet quality have been associated with chronic disease risk and health outcomes.
This paper presents preliminary work in developing an Australian DQI, named the Australian Healthy Eating Index (Aust-HEI). The Aust-HEI is based on previously published DQIs and adapted for use with nutrition data from a food frequency questionnaire and short dietary questions. This preliminary work utilises data from the 1995 National Nutrition Survey (NNS) food frequency questionnaire (FFQ) and short dietary questions (SDQ). The Aust-HEI focuses on usual consumption of food and dietary behaviours, and consists of seven variables representing three dietary aspects—dietary variety, fruit and vegetable consumption, and fat (particularly saturated fat) consumption. These three elements have all been shown to relate to chronic disease risk, and are weighted equally in the Aust-HEI.
Application of the Aust-HEI would enable the derivation of a single measure for healthy dietary behaviours (particularly in relation to chronic disease risk) from a survey incorporating a limited nutrition component. While this would not take the place of collecting detailed nutrition data, it would enhance presentation and interpretation of data collected in more general surveys.
As there are no Australian longitudinal data with which to assess chronic disease outcomes in relation to the Aust-HEI scores, this preliminary work was developed to have construct validity (i.e. in the derivation of each score and its relation to the overall score) and was assessed for internal consistency. As a measure of healthy dietary behaviours, the Aust-HEI demonstrates internal consistency and construct validity. Individuals scoring low on any one component tend to score low overall, which implies that the overall DQI score provides a balanced representation of all three elements. It also suggests that the derivation of each component score is logical.
To follow on from this preliminary work, validation of the Aust-HEI using longitudinal data on morbidity or mortality outcomes is recommended. Existing data sources, such as the Australian longitudinal study on women’s health, should be investigated as a possible source of such data. In addition, for future survey analysis to utilise the Aust-HEI most effectively, the model proposed here should be refined in conjunction with the development of a new FFQ that better reflects current food choices.
It appears that use of the Aust-HEI to derive a comprehensive measure for dietary behaviour would add value to chronic disease risk factor monitoring, as it is a relatively robust and internally consistent summary measure of healthy dietary behaviours. By using both a FFQ and SDQ, the Aust-HEI provides an indication of a range of dietary choices and behaviours, by addressing dietary variety, fruit and vegetable consumption, and saturated fat consumption.