As nutrition and sustainability continue to converge, it is important to examine the existing evidence highlighting the environmental benefits of soyfoods.
Nutrition is the process of taking in food and using it for growth, metabolism, and repair. Historically, to become a nutrition expert, one must develop a solid background in biochemistry and physiology, and to varying degrees, learn about foods. But according to the Society for Nutrition Education and Behavior (SNEB), a nutritionist also needs to know a thing or two about climate change.
Greater understanding of climate change may in turn lead to greater awareness of soyfoods. While there is debate about the precise contribution of agriculture to climate change and assessing the environmental impact of foods is a developing science, accumulating evidence indicates soyfoods have a role to play in reducing greenhouse gas (GHG) emissions.
The position of the Society for Nutrition Education and Behavior is that “environmental sustainability should be inherent in dietary guidance, whether working with individuals or groups about their dietary choices or in setting national dietary guidance.”1 This position aligns with that of the Food and Agriculture Organization (FAO) of the United Nations, which recently established 17 Sustainable Development Goals (SDGs) that can be broadly organized around 4 principal domains: nutrition, economics, society, and the environment.
Soyfoods may play an especially important role as sources of protein that minimally contribute to GHG emissions in comparison to other protein sources. This advantage pertains to both the traditional soyfoods and foods based on soy protein ingredients (soy protein isolate and soy protein concentrate) such as soy-based burgers.
Greenhouse gases absorb and emit radiant energy within the thermal infrared range, causing the greenhouse effect. In simple terms, greenhouse gases trap heat and make the planet warmer. The three main greenhouse gases are nitrous oxide, methane, and carbon dioxide. Since these gases do not all trap heat to the same extent, a common measure was developed to compare the emissions from various greenhouse gases based on their global-warming potential (GWP), by converting amounts of other gases to the equivalent amount of carbon dioxide with the same GWP. Hundreds of studies have evaluated the GWP of foods and overall diets.
In 2011, Gonzalez et al.2 determined that of the more than 20 animal and plant sources evaluated, growing soybeans was the most environmentally advantageous way to produce protein. This determination was based on the protein delivery efficiency (energy input required to grow and harvest soybeans) and the GHG emissions (kg CO2 equivalents) per gram protein. Since proteins differ in quality, Tessari et al.3 considered amino acid content in their evaluation of the land use and GHG emissions associated with different protein sources. They concluded that “the theoretical advantage of producing vegetal rather than animal proteins, is either markedly blunted, abolished or even reverted, with the notable exceptions of soybeans.” The approach adopted by Tessari et al.3 can be debated, since proteins are not consumed in isolation, but the comments related to soybeans are notable nonetheless.
While soybeans can be boiled and eaten in the same way as other dried beans, throughout much of the world, soy is consumed in the form of the traditional Asian soyfoods such as tofu and soymilk. Since additional processing steps are involved in the making of these foods, a true environmental assessment of soybeans as a source of protein should consider the ramifications of these additional processes. Doing so led to a 2018 paper by Poore and Nemecek,4 which reported that on a per 100 g protein basis, beef resulted in 25 times more GHG emissions than tofu and required about 75 times more land. Cow’s milk resulted in 3.2 times more GHG emissions than soymilk and requires almost 13 times more land.
Finally, in much of the Western world, in addition to the traditional soyfoods, soy is consumed in the form of meat analogues. Research also shows these products have advantages over their meat counterparts. For example, van Vliet et al.5 reported that GHG emissions were about 4 times greater for feedlot-finished beef in comparison to one of the more popular soy-based burgers. Also, GHG emissions (CO2 kg/kg protein) associated with soy protein isolate (which is by definition at least 90% protein), whey protein concentrate, chicken and pork were 2.4, 16, 17, and 24, respectively.6
In summary, emerging evidence highlights the environmental advantages of soyfoods. These advantages may increasingly factor into the view health professionals have of these foods.
- Rose D, Heller MC, Roberto CA. Position of the Society for Nutrition Education and Behavior: The importance of including environmental sustainability in dietary guidance. Journal of nutrition education and behavior. 2019;51:3-15 e1.
- González AD, Frostell B, Carlsson-Kanyama A. Protein efficiency per unit energy and per unit greenhouse gas emissions: Potential contribution of diet choices to climate change mitigation. Food Policy. 2011;36:562-70.
- Tessari P, Lante A, Mosca G. Essential amino acids: master regulators of nutrition and environmental footprint? Scientific reports. 2016;6:26074.
- Poore J, Nemecek T. Reducing food’s environmental impacts through producers and consumers. Science. 2018;360:987-92.
- van Vliet S, Kronberg SL, Provenza FD. Plant-based meats, human health, and climate change. Frontiers Sustainable Food Systems. 2020;4.
- Braun M, Muñoz I, Schmidt JH, et al. Sustainability of soy protein from life cycle assessment. FASEB J. 2016;30:894.5.