The Dietary Guideline Index (DGI) [1
] is a comprehensive food-based diet quality index that reflects adherence to the Dietary Guidelines for Australian Adults [2
]. It has been shown to have an inverse relationship with daily fat and energy consumption and a positive relationship with dietary fiber and important micronutrients such as vitamin C, folate, calcium, and iron [1
]. A higher Dietary Guideline Index score has been associated with reduced risk of Type 2 diabetes, hypertension and obesity [4
], and people with a higher score have demonstrated less weight gain over 15 years compared to those with a lower score [6
]. In 2013, the Australian National Health and Medical Research Council released revised Australian Dietary Guidelines (ADG) [7
] based on an updated review of the scientific evidence [8
]. A revision of the Dietary Guideline Index is necessary in order to capture key changes to the guidelines in this measure of diet quality.
Increased longevity combined with the ageing of the baby boomers is leading to growth in the proportion of older people worldwide [9
]. Older adults are an understudied population in nutrition, however, research suggests that poor diet quality among this population is associated with reduced quality of life [10
], increased cardiometabolic risk [4
], and increased risk of mortality [13
]. It is important that older adults maintain good health and quality of life to continue their active contribution to society and to manage the economic pressures of growing health and aged care service demand [9
]. An estimated 80% of health problems associated with old age could be prevented or postponed through lifestyle change and interventions within 50+ age groups are likely to provide benefits [14
]. Peri-retirement is a transitional period of life where adults may experience changes in lifestyle, including changes in family dynamics and employment. These events have potential to influence behaviours such as diet [15
]. Exploring diet quality in peri-retirement aged adults (defined as 55–65 years) will help identify adults at risk of poor diet and will also help shape preventative campaigns that target at risk groups during a time of life in which lifestyle changes are likely to occur.
The aims of this paper are to revise the Dietary Guideline Index (DGI-2013) and to examine the diet quality of peri-retirement aged adults by examining the DGI-2013’s associations with key sociodemographic characteristics, health-related behaviours and body mass index (BMI).
The DGI-2013 is a revised tool that can be used for assessing diet quality of Australian adults based on the Australian Dietary Guidelines. In a sample of peri-retirement aged Australians, a higher diet quality was associated with being female, higher education, not smoking, meeting physical activity guidelines and a lower BMI. These results are consistent with previous studies [1
]. Among the peri-retirement aged adults, overall compliance with the dietary guidelines was poor. Both men and women showed the least compliance with guidelines for limiting discretionary food, followed by the food variety and vegetable components, and they showed greatest compliance with moderating unsaturated-fat and alcohol intake.
Our results suggest that men from urban areas had higher diet quality than those from rural areas. Perhaps men are influenced by rural-related disadvantage such as access and availability of nutritious food [35
], while women, tending to be more health conscious [36
], are more likely to overcome these barriers. It is interesting that men who worked part-time or less had higher diet quality than those working full-time. Lack of time and competing priorities is perceived as a barrier to healthy eating [37
], and, therefore, those who work may have less time to focus on healthy eating. However, income is also a determinant of diet quality [38
], and may be important in peri-retirement adults who experience a drop in income as they change work-loads or retire [39
]. Little is known about the economic determinants of diet among older adults [40
]. There may be complex interactions between diet and socioeconomic exposures, particularly during a life-stage transition such as peri-retirement.
We found a higher diet quality was associated with lower BMI. This is consistent with previous cross-sectional [41
] and longitudinal studies [6
]. Furthermore, the DGI-2013 has been positively associated with health-related quality of life at two-years in the WELL study sample [11
]. This demonstrates convergent validity consistent with the original Dietary Guideline Index, with adherence to the DGI-2013 protecting against negative health-outcomes, a goal of the ADG [7
]. However, further work, particularly in longitudinal analyses, is required to confirm these findings.
Another key finding of this study is that only 31% of men and 53% of women were meeting the daily intake recommendation for lean meat and alternatives, a protein-rich food group. This is substantially lower than earlier results reported from an Australian adult population (19 years old) in which 87%–90% of men and women met the previous guideline [1
]. This is concerning for this age group given protein is important to help maintain muscle mass [44
]. Low compliance rates were also observed for the fruit, vegetable and cereal guidelines, consistent with other studies [1
There are a number of considerations to address when developing and using diet quality indices, including decisions regarding the components or indicators for inclusion in the index [30
]. Previous diet quality indices have incorporated fish consumption as an isolated component of their score due to evidence to support the health benefits of fish [30
]; however, this is not included in the DGI-2013 [46
]. The components in the DGI-2013 were guided by the ADG [7
] which do not include daily intake recommendations for fish. Fish serves are counted towards the serves of lean meat and alternatives. Considerations were made regarding whether the DGI-2013 should include a component reflecting recommendation to substitute poly- and mono- unsaturated fatty acids for saturated fatty acids. Previous dietary indices have included a ratio of fat types [30
]. It is unclear if there are equivalent health effects for poly- vs.
mono- unsaturated fatty acid consumption and similarly for omega-3 fatty acid vs.
], and perhaps a more complex indicator would be required [30
]. In addition, the DGI is designed as a food-based score, people consume whole foods rather than individual nutrients and therefore nutrient-based indicators were not included. Instead, the moderate unsaturated fat component was included inline with the ADG recommendation to include a small allowance of unsaturated oils, fats and spreads. Consideration of alcohol consumption has previously been highlighted as contentious with a suggestion that non-consumers should be disadvantaged in the diet quality scoring system, due to the evidence of positive effects of moderate intake [30
]. However, these findings have been challenged and the ADGs maintain that abstainers have better health outcomes than heavy drinkers [7
This study has a number of strengths and limitations. Firstly, the results were limited by the modest response rate (38%); however, the participant characteristics were comparable to national population statistics. For example, the WELL study participants had similar levels of employment in comparison to national figures (60% vs.
61% in full time or part time employment) and they were marginally more highly educated (28% vs.
19% completing a university degree or higher). Participants were less likely to be overweight or obese in comparison to national data (64% vs.
74%) and were less likely to be current smokers (12% vs.
]. Similar proportions of the WELL sample were meeting fruit (10% vs.
11%) and vegetable (61% vs.
56%) recommendations compared to the national population of the same age [45
The cross-sectional nature limits this study, as a causal relationship cannot be assumed. The applications of the DGI-2013 in the WELL study was also limited by the available dietary intake data, in particular, there was no information collected on portion sizes to compliment the FFQ data; however, this is consistent with previous applications of the DGI [1
]. There were few foods that could be used as indicators of unsaturated fat intake; and participants following a vegetarian diet were not identifiable and, therefore, they may have been disadvantaged in the score calculation. However, the 2011–2012 Australian Health Survey found that only 2% of 51 to 70 years old avoid meat [45
] minimising implications on our findings.
The use of the food-based index to assess diet quality is a significant strength as diet research has shifted from exploring individual nutrients to whole foods and food patterns, to account for the interactions of the nutrients and non-nutrient components of foods in vivo
]. Another strength was the use of a diet quality tool that has previously been shown to reflect intake of key nutrients and discriminate across varying socioeconomic factors, health behaviours and health outcomes [1
]. This study updated this tool so that it reflects the best scientific evidence available [7
]. Exploring this understudied population of peri-retirement aged adults is a significant aspect of this work as it helps improve our understanding of diet within the context of a unique life stage.