Using a personalised nutrition approach to deliver and evaluate sustainable healthy diets

Following a lower-impact, or more ‘sustainable diet’, is expected to improve the environment and human health. However, the question remains as to whether required dietary changes are acceptable and will meet nutrient requirements for all. Personalised nutrition interventions show promise for greater and more long-term dietary change. This thesis will develop and evaluate personalised nutrition feedback for a more sustainable healthy diet. A sustainable diet and corresponding personalised feedback framework were developed and tested before use in the MyPlanetDiet randomised controlled trial. The primary outcome of MyPlanetDiet was a reduction in diet-related greenhouse gas emissions (GHGE). Healthy adults following moderate-to-high GHG-emitting diets were randomised to receive personalised feedback based on a sustainable diet (intervention) or based on Healthy Eating Guidelines (control) for 12 weeks. Dietary assessments (24-hour recalls), fasting serum samples (clinical chemistry), and fasting anthropometry were collected at baseline and endpoint. At baseline, participants (n=355) who adhered to more HEG had lower diet-related GHGE, higher diet quality, and more favourable anthropometry. The MyPlanetDiet intervention group significantly decreased diet-related GHGE over the 12-week study period (p=0.003) and compared to the control group (p<0.001). Control and intervention groups (n=292) had higher diet quality, intakes of fruits, vegetables, fish, and legumes, and lower intakes of red meat, poultry, pork and eggs at endpoint. There were no differences between groups or over time in metabolic markers during the study. Participants were clustered into metabolic phenotypes based on baseline concentrations of total cholesterol, HDL-cholesterol, triacylglycerides and glucose. Three distinct metabolic phenotypes were identified, and two phenotypes exhibited positive metabolic response during the study. Overall, a more sustainable diet is achievable with no negative health effects at least in the short-term and positive metabolic health outcomes for sub-groups. This thesis supports the effectiveness and safety of following a more sustainable diet.