Evidence-to-practice gap in the translation of dietary intake advice for the prevention of cardiovascular disease

Research Doctorate - Doctor of Philosophy (PhD)The term cardiovascular disease (CVD) covers a wide range of conditions that affect the heart and blood vessels, the most recognised of which are myocardial infarctions (heart attacks) and strokes. CVDs may be acute or chronic and approximately 21% of Australian adults were affected by CVD in 2011-2012. A key strategy in CVD prevention and treatment is addressing modifiable risk factors, including those conferred by lifestyle such as smoking status, physical activity levels and nutrition. Dietary patterns influence several biomedical CVD risk factors such as high blood pressure, serum cholesterols, high body mass and type II diabetes. However, modifying dietary patterns to align with National recommendations for preventing chronic diseases such as CVD involves many environmental, social and individual factors that impact on food choices. The translation of current best evidence for the prevention and treatment of CVD needs to account for a wide range of individual influences and be applicable to a wide range of population groups. The aims of this thesis were to assess gaps in the process of translating best-practice nutrition and dietary evidence to populations who may benefit from interventions targeting prevention of CVD events. The process was assessed in four areas of the translation spectrum: Eating patterns that contribute to the evidence for prevention of CVD. ; Strategies that may be used by clinicians and practitioners to translate current evidence. ; Identification of populations at increased risk of CVD that may be amenable to changes in dietary patterns. ; Quantification of translation of best-practice evidence by measuring long-term changes in dietary patterns efficacious for CVD prevention. The literature review identified that unsaturated fats and unrefined carbohydrates are the macronutrients most likely to influence the underlying biomedical factors, which play a role in CVD development. Eating patterns with increased intakes of unrefined plant-based foods, such as the Mediterranean, Portfolio and DASH diets contain the types of fats and carbohydrates that are most beneficial to CVD health. Characteristics that make these eating patterns unique, such as the high unsaturated to saturated fat intake of the Mediterranean diet, the use of functional and nutraceutical foods of the Portfolio diet (soy foods and products containing plant sterols), and the low sodium focus of the DASH diet also individually contribute to reducing dietary CVD risk. A systematic review of the literature was used to identify dietary interventions that had translated dietary evidence to populations with or at high risk of CVD or health professionals who were most likely to treat CVD patients. The results of the review aimed to inform strategies undertaken in two dietary translation studies in populations at high risk of CVD. The strategies identified in the published studies were of limited value in informing the best approach as few studies provided sufficient details regarding how the translation was accomplished. Identification of populations at increased risk of CVD, who may be amenable to changing their dietary pattern in terms of CVD risk, was investigated through two secondary data analyses and two intervention studies. Both secondary data analyses assessed diet-related CVD risk in young people (< 15 years old) with at least one risk factor for CVD previously identified. The first investigated associations between dietary intakes, anthropometric and serum lipid data in prepubertal children with overweight or obesity as the known CVD risk factor. Results from this analysis indicated an association between multiple risk factors for CVD and dietary intakes in boys, with no association found in girls. The other secondary data analysis investigated low socioeconomic status as a CVD risk factor in a population of adolescent girls. The dietary patterns of the girls were shown to be sub-optimal, with 47% of the girls’ dietary intakes being derived from energy-dense, nutrient-poor food and few girls meeting dietary guideline recommendations. The intervention studies translated current evidence-based dietary advice to two different populations at increased risk of CVD. The first study targeted families with a demonstrated family history of CVD. This allowed both adults and children who may share genetic risks and lifestyle behaviours within a home environment to be targeted. This study identified that CVD risk in this particular population was not always accurately perceived. Also, many influences, including facilitators and barriers were demonstrated to impact on family and individual eating patterns. However, families were able to make a number of small dietary changes within their home environment. The second intervention study tested the translation of evidence-based dietary advice on serum lipids in a population who self-identified as at increased risk of CVD through increased serum cholesterol. The dietary advice delivered in a single personalised counselling session achieved reductions of 0.51mmol/L in total cholesterol, 0.28 mmol/L in LDL cholesterol and 0.38 mmol/L in triglycerides over an average of 9.5 ± 2.5 weeks. This was most likely mediated through a 1006kJ per day reduction in energy from nutrient poor foods. The final area of research in this thesis was the validation of a method of measuring the translation of dietary advice for the prevention of CVD by quantifying efficacious changes in the dietary patterns of individuals at increased risk of CVD. A food frequency questionnaire (FFQ) previously validated in a healthy population was modified to include additional food items specifically associated with heart health. Dietary estimates were provided using both the original and modified versions of the FFQ by 39 study participants who self-identified as having increased serum cholesterol levels. Better estimates of dietary fatty acid intakes were achieved using the modified FFQ. Populations who identify as having CVD health conditions may be regularly consuming foods or supplements regarded as beneficial to that condition but which have been inadequately assessed using standard dietary assessment measures. This thesis identified that there are gaps in the current translation of dietary evidence for the prevention of CVD where improvements may be possible. Although dietary patterns are considered a modifiable risk factor, adapting intakes towards dietary recommendations for improving heart health remains challenging. However, dietary modifications can be an effective component of primary and secondary CVD prevention and effective strategies that translate evidence-based dietary advice for populations with or at risk of CVD are needed