Evaluating the environmental impacts of dietary recommendations

Nationally recommended diets are a prominent method for informing the public on dietary choices. Although dietary choices drive both health and environmental outcomes, the authors found that very few recommendations mention environmental impacts. Even though these recommendations don’t specifically mention environmental outcomes, they still might be better than other diets simply on the basis of health advice. The authors found that following a nationally recommended diet in high-income nations results in a reduction in greenhouse gases, eutrophication, and land use. In upper-middle–income nations, they found a smaller reduction in impacts, and in lower-middle–income nations the they found find a substantial increase (see figure 3 in the paper, figure 1 below).

Figure 1. Relative differences in environmental impacts between nationally recommended and average diets for high-income and lower-income nations. Red line indicates median relative difference; left and right box limits show first and third quartiles, respectively; whiskers show range from minimum to maximum; and blue crosses show the mean, population-weighted impact.
 

The method they used was an environmentally-extended input-output model, unified with FAO data. Typical approaches use LCA to make calculations of this type. The weakness of the authors’ approach compared to LCA is the coarseness of the food groups (12 in this study, and aggregated to 6 for reporting), but the advantage is the fact that the researchers could follow the environmental impacts through the global supply chain, and get nation specific estimates on the consumption-based environmental impacts. This, and the fact that the authors were able to include many middle-income nations is a major strength of the article.

The work shows that impacts vary around the world, depending on national income and dietary patterns. There are a number of findings in the paper in specific cases, but in general the work will help policy makers in future work to further optimize nationally recommended diets.

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 PO₃⁻⁴ 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.
 

Reference

Behrens, P., Kiefte-de Jong, J. C., Bosker, T., Rodrigues, J. F. D., Koning, A. de, and Tukker, A. (2017). Evaluating the environmental impacts of dietary recommendations. Proceedings of the National Academy of Sciences of the United States of America. DOI: 10.1073/pnas.1711889114 .

You can find the article here (open access).

For media coverage of the study results, see 'UK could cut food emissions by 17% by sticking to a healthy diet' (Carbon Brief) and 'Eating for your health is also better for the environment, study shows' (LA Times).

Also, see the 2016 FCRN and FAO report 'Plates, pyramids and planets' (pdf) on developments in national healthy and sustainable dietary guidelines.