Evaluating the environmental impacts of dietary recommendations

Dietary choices drive both health and environmental outcomes. Information on diets come from many sources, with nationally recommended diets (NRDs) by governmental or similar advisory bodies the most authoritative. Little or no attention is placed on the environmental impacts within NRDs. Here we quantify the impact of nation-specific NRDs, compared with an average diet in 37 nations, representing 64% of global population. We focus on greenhouse gases (GHGs), eutrophication, and land use because these have impacts reaching or exceeding planetary boundaries. We show that compared with average diets, NRDs in high-income nations are associated with reductions in GHG, eutrophication, and land use from 13.0 to 24.8%, 9.8 to 21.3%, and 5.7 to 17.6%, respectively. In upper-middle-income nations, NRDs are associated with slight decrease in impacts of 0.8-12.2%, 7.7-19.4%, and 7.2-18.6%. In poorer middle-income nations, impacts increase by 12.4-17.0%, 24.5-31.9%, and 8.8-14.8%. The reduced environmental impact in high-income countries is driven by reductions in calories (similar to 54% of effect) and a change in composition (similar to 46%). The increased environmental impacts of NRDs in low- and middle-income nations are associated with increased intake in animal products. Uniform adoption of NRDs across these nations would result in reductions of 0.19-0.53 Gt CO2 eq.a(-1), 4.32-10.6 Gt PO43- eq.a(-1), and 1.5-2.8 million km(2), while providing the health cobenefits of adopting an NRD. As a small number of dietary guidelines are beginning to incorporate more general environmental concerns, we anticipate that this work will provide a standardized baseline for future work to optimize recommended diets further.