Assessment of the Environmental Impact of Food Consumption in Ireland—Informing a Transition to Sustainable Diets

Dietary changes are required to mitigate the climatic impact of food consumption. Food consumption databases can support the development of sustainable food based dietary guidelines (SFBDG) when linked to environmental indicators. An improved knowledge base is crucial to the transition to sustainable diets, and multiple environmental indicators should be considered to ensure this transition is evidence based and accounts for trade-offs. The current study aimed to quantify the environmental impact of daily diets across population groups in Ireland. Nationally representative food consumption surveys for Irish children (NCFSII; 2017–2018), teenagers (NTFSII; 2019–2020), and adults (NANS; 2008–2010) were used in this analysis. Blue water use (L) and greenhouse gas emissions (GHGe; kgCO₂eq) were assigned at food level to all surveys. Cropland (m²), nitrogen (kgN/t), and phosphorous use (kgP/t) were assigned at the agricultural level for adults. Multiple linear regressions, Spearman correlations, and ANCOVAs with Bonferroni corrections were conducted. Higher environmental impact diets were significantly associated with demographic factors such as age, education status, residential location, and sex, but these associations were not consistent across population groups. The median greenhouse gas emissions were 2.77, 2.93, and 4.31 kgCO₂eq, and freshwater use per day was 88, 144, and 307 L for children, teenagers, and adults, respectively. The environmental impact of the Irish population exceeded the planetary boundary for GHGe by at least 148% for all population groups, however the boundary for blue water use was not exceeded. Meat and meat alternatives (27–44%); eggs, dairy, and dairy alternatives (15–21%); and starchy staples (10–20%) were the main contributors to GHGe. For blue water use, the highest contributors were meat and meat alternatives in children; savouries, snacks, nuts, and seeds in teenagers; and eggs, dairy, and dairy alternatives in adults (29–52%). In adults, cropland use, nitrogen use, and phosphorous use exceeded planetary boundaries by 277–382%. Meat, dairy, and grains were the main contributors to cropland, nitrogen, and phosphorous use (79–88%). The quantified environmental impact of Irish diets provides a baseline analysis, against which it will be possible to track progress towards sustainable diets, and the basis for the development of Sustainable Food Based Dietary Guidelines in Ireland.