Overconsumption of energy and excessive discretionary food intake inflates dietary greenhouse gas emissions in Australia

Population dietary guidelines have started to include information about the environmental impacts of food choices, but more quantifiable evidence is needed, particularly about the impacts associated with discretionary foods. This paper utilised the 2011-2012 Australian Health Survey food intake data along with a highly disaggregated input-output model to estimate the greenhouse gas emissions (GHGe) of Australians' dietary intake, and compare current patterns of eating which vary in diet quality and GHGe to the recommended diet. The average dietary GHGe were 18.72 ± 12.06 and 13.73 ± 8.72 kg CO₂e/day for male and female adults, respectively. The correlation between total energy and GHGe was r = 0.54 (p < 0.001). Core foods contributed 68.4% and discretionary foods 29.4%. Within core foods, fresh meat and alternatives (33.9%) was the greatest contributor. The modelling of current dietary patterns showed the contribution of discretionary foods to GHGe was 121% greater in the average diet and 307% greater in the "lower quality, higher GHGe" diet compared to the recommended diet. Reducing discretionary food intake would allow for small increases in emissions from core foods (in particular vegetables, dairy and grains), thereby providing a nutritional benefit at little environmental expense. Public health messages that promote healthy eating, eating to one's energy needs and improved diet quality will also contribute to lowering GHGe.