Doctor of Philosophy (PhD)
Department of Biomedical Science - Faculty of Health & Behavioural Sciences
Gillen, Lynda Jacqueline, The effectiveness of structured food pattern advice for achievement of macronutrient targets in nutrition intervention, PhD thesis, Department of Biomedical Science, University of Wollongong, 2005. http://ro.uow.edu/theses/337
Dietary advice to individuals in Medical Nutrition Therapy for the prevention and treatment of disease should be based on the best available evidence. A review of the evidence identifies appropriate nutrients on which to base advice. However, evidence to support the application of advice for the achievement of nutrient targets in free-living individuals has not been adequately determined. In this doctoral program the hypothesis tested was that structured advice based on the pattern of intake from food group sources of required nutrients will result in better achievement of dietary targets and thereby clinical outcomes than advice based on existing core food guides. In developing a more comprehensive food guidance system, nutritional therapy for diabetes treatment provides an appropriate example in which individual macronutrients and the type of fat are targets of advice. A cross-sectional survey of the food habits of a sample of women with Gestational Diabetes Mellitus was conducted to confirm the relevance of food patterns to specific clinical outcomes, in this case, glucose tolerance. Secondly, foods commonly consumed by these women enabled the identification of food groups likely to impact on macronutrient and fat profiles within the diet. Subsequent determination of a total diet model demonstrated that a structured approach to dietary advice relating to nine food groups (vegetables, starch, fruit, milk, soymilk, meat, oily fish/soybeans, monounsaturated and polyunsaturated fats) for the identification of sources of saturated and unsaturated fats would achieve nutritional adequacy and targets for energy and individual macronutrients with minimal variation. This then formed the basis of individualised advice in dietary intervention trials. Applying the newly developed advice system in an intervention trial demonstrated its feasibility in women with Gestational Diabetes Mellitus. Compared with a similar group receiving standardised low fat advice, 80% achieved saturated and polyunsaturated fat targets compared with nil in the standard intervention group, without detrimental changes to the overall macronutrient profile. The clinical effectiveness of the advice system was again demonstrated in a second trial. In this study men and women with Type 2 Diabetes Mellitus followed two alternative patterns of advice based on the newly developed food guidance system for six months. In these two groups respectively, 79% and 100% of subjects, achieved targeted proportions of total polyunsaturated fat compared to 25% in a control group (p(less than)0.05). In addition, greater improvements were achieved for HDL cholesterol (+18% and +21% compared to +13% control, p(less than)0.05) and triglyceride levels (-12% and -11% compared to -2% control). In summary, this thesis has outlined the development and evaluation of an advice system to support nutrition intervention in people with diabetes. Individualised advice based on a structured food pattern identifying food group sources of target nutrients was both feasible to implement and effective in practice. The application of this knowledge will help support nutrition intervention research as well as provide an evidence-based approach to Medical Nutrition Therapy.