Building an evidence base towards sustainable diets in the Irish population

Background: Climate change, food demand and diet-related disease underline an urgent need for more sustainable and healthy food practices. Dietary guidance in the form of Sustainable Food Based Dietary Guidelines have been recommended at a national level to mitigate the environmental impact of food consumption, while improving health. For the Irish population to transition to sustainable diets, an improved knowledge base is required on the quality of current dietary patterns and the environmental impact of such. Objective: This thesis was designed to analyse diets reported in the Irish Population from a nutrition, environment, and cost perspective, and to complete preliminary modelling of healthier and more sustainable diets for sub-groups of the population. Methods: Food intakes on children, teenagers, and adults were taken from IUNA food consumption databases (FCDB). Nutrient based diet quality scores were calculated and evaluated as a metric of diet quality. Environmental data on greenhouse gas emissions and water use were taken from a UK life cycle assessment study, and agricultural impacts (cropland, nitrogen, and phosphorous use) from the FAOSTAT database to adults. A food price database was compiled, and dietary optimisation was completed using FICO Xpress software. Results: An evidence base was created by assigning three nutrient based scoring systems and linking data on environmental factors and food price to the FCDBs. In the nutritional analysis, teenagers and young adult females had significantly lower nutritional adequacy than the rest of the Irish population (58% probability of meeting nutrient recommendations). Lower nutritional adequacy was highlighted in females, those with a lower education level, and those from a more urban location. The Irish population was found to exceed planetary boundaries for GHGe (by up to 226%) but were well within the planetary boundaries for water use (<40%) across all groups. In relation to the agricultural boundaries, adult diets exceeded planetary boundaries considerably for all factors, from 277% - 382%. Dietary expenditure was found to be linked to life stage, and average cost ranged from €3.80 to €11.70 per day. Healthier diets were found to be more expensive (by €1.82 to €4.74 per day) and adults in education had a significantly higher dietary expenditure than all other social class groups (€10.90 per day). Dietary expenditure was found to be directly associated with environmental impact, and this may present a secondary motivation for consumers to transition to sustainable diets in Ireland. Affordable, environmentally, and nutritious food categories (e.g., milk, potatoes, cruciferous vegetables) and foods with multiple negative benefits were identified (unprocessed white meat and dishes, meat alternatives and dishes, vegetable soup and dishes, high energy beverage.). In the dietary modelling, GHGe reductions varied between population sub-groups (45% to 67%) and improvements of nutrient intakes ranged from 20% to 56% closer to nutrient recommendations. Several nutrients were improved from baseline diets in the Irish population (e.g., folate, iodine, and vitamin E) although inadequacy was introduced for nutrients in some population groups (e.g., biotin, cobalamin, and selenium). Conclusion: This thesis includes an in-depth analysis of nutrient intakes, environmental impact, and dietary expenditure across the Irish population and successfully trialled a methodology for integrating these factors to design sustainable diets which consider dietary preferences. The diversity of consumption patterns, nutritional needs, environmental impact, and dietary expenditure found between sub-groups highlight a need for context-specific research and subsequent guidelines.