Evaluating the GHG emissions, land use, and water use associated with contemporary dietary patterns in the Republic of Ireland

Dietary patterns are intrinsically linked to greenhouse (GHG) emissions, land use, and water use via food production systems. Analysing and comparing contemporary dietary patterns and their environmental impact is critical to identifying which should be promoted to enhance global sustainability. A cross-sectional survey of adult consumption patterns was conducted across Ireland with a representative sample size of 957 respondents. Subsequently, a farm-to-fork life cycle assessment (LCA) was employed via OpenLCA 2.0.4 to assess three primary environmental impacts (global warming, land use, and water use) across the population. Thirteen distinct dietary patterns were analysed: total population, rural, urban, self-reported (omnivore, flexitarian, pescatarian, vegetarian, and vegan), and data-derived ('meat-focused', 'dairy/ovo-focused', 'vegetable-focused', 'seafood-focused', and 'potato-focused'). Mean calculated diet-related GHG emissions were 5.52 kgCO₂eq person^-1 day^-1, with the 'meat-focused' diet representing the highest (6.62 kgCO₂eq person^-1 day^-1) and the vegan diet being the lowest (2.0 kgCO₂eq person^-1 day^-1). The 'meat-focused' diet was also associated with the highest per capita land use. The estimated mean water usage was 104 L person^-1 day^-1, with the 'potato-focused' diet using the most water and the pescatarian diet using the least. Future (2050) dietary scenarios compared to 'business-as-usual' patterns were projected; findings suggest substantial environmental impact reductions could be achieved if segments of the Irish population transition to vegetarian, vegan, and 'vegetable-focused' diets. The authors consider that employing data-derived dietary patterns (as opposed to "traditional" dietary classification) in LCA studies may yield increasingly accurate results, as dietary definitions vary significantly between individuals.