Abstract
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 (~54% of effect) and a change in composition (~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 PO4 eq.a−1, and 1.5–2.8 million km2, 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.
Generated Summary
This research quantifies the environmental impact of nationally recommended diets (NRDs) compared to average diets across 37 nations, representing 64% of the global population. The study focuses on greenhouse gases (GHGs), eutrophication, and land use, given their impacts on planetary boundaries. The methodology involves analyzing nation-specific NRDs against average diets, using a consumption-based approach that considers both local and global environmental impacts. Data on dietary composition and recommendations were collected from various sources, including governmental and advisory bodies. These dietary data were then coupled with a multiregional, environmentally extended, input-output (MRIO) database to assess the environmental impacts associated with different diets. The study also includes an isocaloric approach, scaling NRDs to match the total caloric intake of average diets while maintaining the original proportions of food categories. The research aims to provide a standardized baseline for future work to optimize recommended diets by assessing and comparing them with the current dietary habits and to understand the effects of shifting to NRDs across different income levels.
Key Findings & Statistics
- Compared to average diets, NRDs in high-income nations are associated with reductions in GHG emissions by 13.0 to 24.8%, eutrophication by 9.8 to 21.3%, and land use by 5.7 to 17.6%.
- In upper-middle-income nations, NRDs are associated with slight decreases in impacts: 0.8-12.2% for GHG, 7.7-19.4% for eutrophication, and 7.2-18.6% for land use.
- In poorer middle-income nations, impacts increase: 12.4-17.0% for GHG, 24.5-31.9% for eutrophication, and 8.8-14.8% for land use.
- The reduced environmental impact in high-income countries is driven by a reduction in calories (approximately 54% of the effect) and a change in diet composition (about 46%).
- The increased environmental impacts in low- and middle-income nations are linked to an increased intake of animal products.
- Uniform adoption of NRDs across the studied nations could lead to reductions of 0.19-0.53 Gt CO2 eq.a¯¹, 4.32-10.6 Gt PO4 eq.a¯¹, and 1.5-2.8 million km² in land use.
- In average diets, GHG emissions significantly increase with income, ranging from 1.1 kg CO2 eq per person per day in lower-middle-income nations to 2.4 kg CO2 eq per person per day in high-income nations.
- Animal products (meat, fish, and dairy) account for 65% to 70% of emissions in the diets of upper-middle- and high-income nations.
- Eutrophication impacts for average diets show a similar pattern, increasing from 13.1 kg PO4 eq per person per day in lower-middle-income nations to 32.1 kg PO4 eq per person per day for high-income nations.
- The average land use in high-income nations was over 3.5 times that of the low-middle-income average.
- If shifts in caloric intake are also considered, the reductions in high-income nations increase to 0.63 kg CO2 eq.p¯¹.d¯¹ (-24.7%), 8.3 kg PO4 eq.p-1.d-1 (-21.3%), and 0.1 ha.p¯¹ (-17.6%).
- The net result of following NRDs for the countries examined here results in reductions of 0.19 Gt CO2 eq.a¯¹ and 4.32 Gt PO4 eq.a¯¹ in an isocaloric estimate and 0.53 Gt CO2 eq.a¯¹ and 10.6 Gt PO4 eq.a¯¹ in a nonisocaloric estimate.
Other Important Findings
- Nationally recommended diets (NRDs) generally recommend a substantial reduction in sugars, oils, meat, and dairy, with the most significant reductions in high-income nations.
- India and Indonesia are the only nations with recommendations for increases in meat intake, potentially due to the prevalence of undernutrition and micronutrient deficiencies.
- The environmental impacts of average diets significantly increase with income.
- Exceptions to the general trends in high-income nations, showing larger increases in environmental impacts, include Poland, South Korea, and Switzerland.
- Brazil and South Africa are exceptions in the middle-income nations, with the former showing large reductions from meat and dairy.
- In general, eutrophication impacts follow a pattern similar to GHG impacts.
- Trade-linked data reveal that diets associated with NRDs increase import dependence in Australia and Canada while reducing import dependence significantly in Japan.
- Further impact mitigation in high-income nations may be achieved by lowering the recommendations for dairy.
Limitations Noted in the Document
- The study acknowledges that the absolute estimates of environmental impacts are slightly lower than those found in the existing LCA literature. This difference is potentially due to the study only considering food-related emissions and omitting those related to cooking, preparation, and waste, and to differences in allocation and aggregation.
- Variations in results could arise from differences in cooking times and technologies not captured in the data.
- The study’s reliance on the EXIOBASE 3.3 database and the specific categorization of food products could introduce limitations.
- The study’s focus on the isocaloric approach, scaling NRDs to match the caloric intake of average diets, may not fully capture the impacts of changes in overall caloric consumption.
- The study does not account for the potential effects of seasonal variations in food production or the impact of local and regional factors on food choices and production methods.
- The assessment of environmental impacts in the study may be influenced by the choice of the MRIO database (EXIOBASE 3.3) and the specific food categories within it, potentially affecting the comparability with other studies.
Conclusion
This research underscores the critical need to incorporate environmental considerations into dietary recommendations. The findings highlight that adopting NRDs in high-income nations can lead to significant environmental benefits, particularly in terms of reducing GHG emissions, eutrophication, and land use. However, the study also reveals that the impact of NRDs varies across income levels, with potential negative environmental consequences in lower-income nations due to increased animal product intake. A key takeaway is the need for NRDs to be adapted to the specific dietary challenges and environmental contexts of different regions. The study emphasizes that the environmental impacts of NRDs are not uniform and that a one-size-fits-all approach is unlikely to be effective. The authors suggest that modifying the recommendations to reduce the consumption of meat, dairy, and fish products, particularly in high-income nations, would be beneficial. The study also points out the necessity for lower- and middle-income nations to adapt their diets, ensuring adequate nutrition while considering the environmental implications. The study emphasizes that incorporating environmental sustainability into dietary guidelines is crucial for improving public health and environmental outcomes. This work stresses that while reductions in food waste and other interventions are important, integrating environmental concerns into national dietary recommendations is essential to support a sustainable food system and mitigate environmental impacts.
IFFS Team Summary
- Comprehensive article regarding diet and climate change – well referenced
- references this article which states that diet accounts for 19-29% of global GHG
- http://www.annualreviews.org/doi/pdf/10.1146/annurev-environ-020411-130608
- developed countries have greater impact on climate due to increased animal product consumption
- concurrent benefit for health and climate if more micro and macronutrients were obtained from plant sources
- news article with some key points:
- http://beta.latimes.com/science/sciencenow/la-sci-sn-dietary-guidelines-environment-20171204-story.html
- “Animal products (meat, fish, and dairy) account for 22%, 65%, and 70% of emissions in the diets of lower-middle–, upper-middle–, and high-income nations, respectively.”