Systematic review on the impacts of dietary change on greenhouse gas emissions, land use, water use, and health

Agriculture is an important driver of environmental change, including water use, land use, and GHG emissions, among other impacts, and adding to the increasing strains on global environmental systems. Dietary change may therefore provide an important route to alleviating some of these environmental impacts, as well as improving health. A growing body of research has examined the environmental impacts of dietary change, using a variety of underlying models, data, and types of dietary change. The authors systematically assessed these studies to summarise this growing and varied area of research.

The review considered 63 studies, which included a total of 210 scenarios of dietary shifts. There were 14 common dietary patterns assessed across the studies included, often referred to as “sustainable diets”. The review showed that reductions above 70% of GHG emissions and land use, and 50% of water use, could be achieved by the assessed dietary changes (with medians of these impacts across all studies showing reductions of between 20–30%). Environmental benefits were largely proportional to the amount of meat reduced. The review also found modest health benefits, though the number of studies examining health outcomes were limited.

While the evidence overwhelmingly pointed to reduced environmental impacts from reduced animal-source foods, there were some examples of trade-offs and complexities (e.g. reduced GHG emissions but increased water use when switching to a vegan diet, and increased emissions and land use from adopting US dietary guidelines high in recommended dairy intakes). The results of this work may only be applicable to high-income countries, and the heterogeneity of diets, production methods, and food systems means that any potential environmental impacts of dietary change will be region- and context-specific. The authors also suggest that future work should begin assessing dietary change against a wider set of indicators, including environmental, as well as economic, health, and sociocultural, to more comprehensively assess their sustainability.

Abstract

Food production is a major driver of greenhouse gas (GHG) emissions, water and land use, and dietary risk factors are contributors to non-communicable diseases. Shifts in dietary patterns can therefore potentially provide benefits for both the environment and health. However, there is uncertainty about the magnitude of these impacts, and the dietary changes necessary to achieve them. We systematically review the evidence on changes in GHG emissions, land use, and water use, from shifting current dietary intakes to environmentally sustainable dietary patterns. We find 14 common sustainable dietary patterns across reviewed studies, with reductions as high as 70–80% of GHG emissions and land use, and 50% of water use (with medians of about 20–30% for these indicators across all studies) possible by adopting sustainable dietary patterns. Reductions in environmental footprints were generally proportional to the magnitude of animal-based food restriction. Dietary shifts also yielded modest benefits in all-cause mortality risk. Our review reveals that environmental and health benefits are possible by shifting current Western diets to a variety of more sustainable dietary patterns.

Reference

Aleksandrowicz, L., Green, R., Joy, E.J.M., Smith, P., Haines, A. (2016) The impacts of dietary change on greenhouse gas emissions, land use, water use, and health: a systematic review. PLoS ONE, 11(11): e0165797. doi:10.1371/journal.pone.0165797

You can find the article here (open access).

If you are interested in sustainable healthy diets, see the FCRN’s paper on this here. Tara Garnett also recently wrote a perspective in Science which you can find here.