In order to assess the success of dietary guidelines, researchers use a measure known as the Dietary Guidelines Index (DGI). This comprehensive food-based index measures diet quality and reflects the adherence of a given population to dietary guidelines. The DGI is continuously updated to reflect any changes made on dietary guidelines based on panel reviews of the latest scientific evidence.
In a recent study, researchers from Australia, Finland and the U.S. sought to improve the DGI currently used in Australia by taking into account the age and sex of a given sample population. To the best of their knowledge, a DGI with consistent scoring across childhood/adolescence (youth) and adulthood has not been validated. The researchers discussed their findings in an article published in the journal Nutrition Research.
American dietary guidelines and Australian dietary guidelines
According to the latest American dietary guidelines, the foods that make up a healthy diet are those that can help a person meet his nutritional needs without exceeding limits. Such foods include fruits, vegetables, whole grains, dairy products, protein-rich foods and sources of healthy fats (e.g., seafood, nuts, seeds). The guidelines recommend eating these foods in their natural forms and not as highly processed food products, which have very low nutritional values.
In addition, the American dietary guidelines also suggest that Americans reduce or limit the amount of saturated fats, added sugars, sodium and total calories they consume. Among popular diets in the U.S., the guidelines consider the Mediterranean diet and the vegetarian diet as perfect examples of a healthy eating pattern. (Related: Study in diet trends reveals that a poor diet is WORSE for your health than drinking and smoking.)
Similar to the American dietary guidelines, the updated 2013 Australian Dietary Guidelines emphasize the consumption of five specific food groups, namely, vegetables and legumes, fruits, grains, lean meats and poultry (protein sources), and dairy products. One of the guidelines' primary objectives is to help Australians achieve and maintain a healthy weight by eating nutritious foods and becoming physically active.
According to Warwick Anderson, CEO of Australia's National Health and Medical Research Council, the Australian dietary guidelines were developed to address the rising incidence of obesity and Type 2 diabetes in the country. By promoting healthy eating and providing research and evidence-based advice, the experts behind these recommendations hope that they can enable Australians to make better dietary decisions to improve their health.
An age- and gender-specific measure of diet quality
In their study, the international team hypothesized that a DGI that reflects age- and gender-specific guidelines could be a valid measure of diet quality in youth and adulthood. They believe that measuring diet quality over time is important due to its huge impact on health.
They based the DGI on the 2013 Australian Dietary Guidelines to reflect the current understanding of diet quality in Australia. The current DGI comprises nine indicators with a maximum score of 100 points.
The researchers calculated DGI scores for participants of the Australian Childhood Determinants of Adult Health study, which included a 24-hour food record during youth (ages 10-15 years) and a 127-item food frequency questionnaire during adulthood (ages 26-36 years).
The researchers also evaluated construct validity (distribution of scores, principal components analysis, correlation with nutrient density of intakes) and criterion validity (linear regression with population characteristics).
The researchers reported that the DGI scores they calculated were multi-dimensional in underlying structure and normally distributed. They found a significant association between a lower DGI among youth and smoking, lower academic achievement and lower socioeconomic status.
DGI scores were also negatively correlated with consumption of calories, sugar and fat, but were positively correlated with consumption of fiber, protein and micronutrients. Among adults, low DGI scores were associated with low education, low self-reported health, high waist circumference, insulin resistance and high total and low-density lipoprotein serum cholesterol.
Based on these results, the researchers believe that their proposed DGI is an appropriate measure of diet quality in youth and adulthood because higher scores reflect nutrient-dense, instead of energy-dense, intake and discriminate between population characteristics in a manner consistent with literature.
Sources include:
EatForHealth.govcms.gov.au [PDF]
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