Abstract
Livestock farming incurs large and varied environmental burdens, dominated by beef. Replacing beef with resource efficient alternatives is thus potentially beneficial, but may conflict with nutritional considerations. Here we show that protein-equivalent plant based alternatives to the beef portion of the mean American diet are readily devisible, and offer mostly improved nutritional profile considering the full lipid profile, key vitamins, minerals, and micronutrients. We then show that replacement diets require on average only 10% of land, 4% of greenhouse gas (GHG) emissions, and 6% of reactive nitrogen (Nr) compared to what the replaced beef diet requires. Applied to 320 million Americans, the beef-to-plant shift can save 91 million cropland acres (and 770 million rangeland acres), 278 million metric ton CO2 and 3.7 million metric ton Nr annually. These nationwide savings are 27%, 4%, and 32% of the respective national environmental burdens.
Generated Summary
This research article presents a comprehensive analysis of the environmental and nutritional impacts of replacing beef with plant-based alternatives in the American diet. The study employs a methodology that combines Monte Carlo sampling and linear programming to create diverse plant-based diets that meet specific nutritional criteria. The authors evaluate various combinations of plant items from a list of 65, ensuring that the diets adequately replace the beef portion of the Mean American Diet (MAD). The research focuses on minimizing environmental burdens such as land use, greenhouse gas emissions, and reactive nitrogen use, while simultaneously satisfying key nutritional requirements. The core approach involves creating and optimizing plant-based diets, quantifying their environmental and nutritional characteristics, and comparing them to the beef-based diet. The study uses data from the United States Department of Agriculture (USDA) and the National Research Council (NRC) to inform its calculations. The primary goal is to assess the potential benefits of dietary shifts towards plant-based alternatives, providing insights into their environmental sustainability and nutritional adequacy. The researchers have aimed to provide a holistic view of the implications of dietary choices on both environmental and human health.
Key Findings & Statistics
- The study found that plant-based replacement diets require on average only 10% of land, 4% of greenhouse gas (GHG) emissions, and 6% of reactive nitrogen (Nr) compared to what the replaced beef diet requires.
- Applied to 320 million Americans, the beef-to-plant shift can save 91 million cropland acres (and 770 million rangeland acres), 278 million metric tons of CO2 and 3.7 million metric tons of Nr annually.
- These nationwide savings are 27%, 4%, and 32% of the respective national environmental burdens.
- U.S. beef yields at most 250 Mcal ac⁻¹ y⁻¹. By comparison, high fructose corn syrup yields 4200 Mcal ac⁻¹ y⁻¹.
- The average American eats 10 and 40 kcal d⁻¹ (≈2.8 and 2.6 kg y⁻¹) of kidney beans and peanuts.
- While on Nov. 2015 various beef cuts ranged in stores throughout the Midwest and the U.S. as a whole over 4-9 dollars lb⁻¹, the same data show that a lb of dried beans and peanut butter were selling for 1.5 and 3 dollars.
- The plant based diets supply no vitamin B12, while the replaced beef supplies 1.7 µg, 71% of the full recommended adult daily intake.
- Beef supplies ≈68% more monounsaturated fatty acids.
- The plant-based diets supply 2.3 and 1.6 mg of zinc, or 23% and 16% of the full recommended adult daily intake.
- The selenium values are 12 and 3 µg, ≈24% and 5% of the full recommended adult daily intake.
- The replaced and replacement diets are essentially interchangeable in terms of vitamins B₂ and B₆.
- If fully reallocated to such wheat and apples while maintaining the current caloric ratio of the two, the 92 million high quality cropland acres that the considered dietary shift stands to spare can thus support a 600% increase in wheat plus apple caloric availability.
Other Important Findings
- Protein-equivalent plant-based alternatives to the beef portion of the mean American diet are readily devisible and offer mostly improved nutritional profile considering the full lipid profile, key vitamins, minerals, and micronutrients.
- The environmental resources the beef and replacement plant-based diets use are compared in Figure 2a-c. Differences in total high quality cropland are enormous, with best estimate + standard error of 1273 ± 417 and 126 ± 35 m² person⁻¹ y⁻¹ for beef and its plant based replacement diets, a 90% land use reduction. The GHG and Nr differences—901 ± 180 vs 33 ± 5 kg CO₂eq person⁻¹ y⁻¹ and 12 ± 2 vs 0.7 ± 0.5 kg Nr person⁻¹ y⁻¹ (94–96% reductions)—are even larger.
- Figure 1 presents statistics of the composition of the 1500 randomized, optimized beef replacing plant based diets (showing means calculated over 500 unique plant combination and the three environmental optimizations). Legumes and peanuts dominate the diets, and reassuringly, leading items in these diets, such as peanuts, lentils, or kidney beans, are consistent with straightforward, authoritative nutritional advice.
- The plant-based diets supply unsaturated fats in quantities that are of no nutritional concern, which is a positive finding.
- The presented shift from beef to plant-based replacement diets can thus improve nutrition in most metrics, with few, easily corrected exceptions.
- The saved high quality cropland acreage nearly equals the ≈91 million total national corn acreage.
- The almost 0.8 billion acres of spared pastureland represent 40% of the contiguous US land surface area, more than the combined area of the three largest states, Alaska, Texas and California.
- The ≈3.7 million metric tons of Nr savings constitute 33% of the total national N fertilizer use, and twice the Mississippi N delivery into the Gulf of Mexico.
- The ≈278 million metric tons CO₂e averted emissions represent 4% and 47% of the U.S. total and direct agricultural (excluding uncertain emissions related to land use changes) emissions.
Limitations Noted in the Document
- The study acknowledges that the chosen plant-based diets are B12 and zinc deficient, minimally selenium insufficient, and supply less monounsaturated fatty acids compared to beef-based diets. However, it points out that these deficits can be easily addressed through supplements.
- The study does not address all relevant environmental impacts, thus further developing performance metrics, especially ones combining nutritional, environmental, and other societal objectives, is essential for devising coherent, readily mutually comparable results and for identifying synergies and trade-offs among varied environmental objectives.
- The authors mention that assuming no further changes to the U.S. agricultural enterprise beyond the considered replacement of beef with plant items or any rebound effect or indirect land use changes arising elsewhere as a response to this shift, this dietary shift can significantly mitigate several major national environmental challenges, such as the Gulf of Mexico Dead Zone, and multifaceted damage to semiarid western lands.
- The deployment prospects of the explored shift may be limited. The authors suggest that the rise of approximate annual per capita beef consumption from 20 to 40 kg over 1930–1980 and subsequent decline to 25 kg in 2012 suggests that U.S. beef consumption strongly responds to economic, demographic, or cultural stimuli, and is more elastic than the above sentiment suggests.
Conclusion
The research concludes that plant-based alternatives to beef offer substantial environmental and nutritional benefits, making a strong case for dietary shifts. The study demonstrates that protein-equivalent plant-based diets can readily replace beef, offering a more favorable nutritional profile while significantly reducing resource use. “Protein, mass and energy conserving plant-based replacements to beef in the U.S. diet are thus readily achievable, and can significantly reduce resource use and improve diet related health outcomes.” The authors emphasize the substantial environmental advantages, including reduced land use, lower greenhouse gas emissions, and decreased reactive nitrogen use. The findings underscore the potential for significant reductions in national environmental burdens, making a strong environmental argument for the shift. The study also highlights that the shift can bring vast agricultural benefits and help restore populations of key species. However, the researchers acknowledge certain nutritional considerations, such as B12 and zinc deficiencies, but suggest that these can be readily addressed. They also note that further research is needed to understand the social and economic implications of such a dietary shift. Despite these limitations, the study presents a compelling case for the adoption of plant-based diets, emphasizing the potential to improve both environmental sustainability and human health. The research points to the practical and significant benefits that a transition towards plant-based diets could bring at a national scale. The authors’ conclusion reinforces the need for societal change and also encourages further research into the nutritional and environmental benefits.