Abstract
Progress towards eliminating hunger and promoting sustainable diets is lagging, with food systems damaging ecosystems and over 700 million people undernourished. Here we develop a linear programming model that identifies food combinations that satisfy both environmental and nutritional constraints. Using US-specific data, the model considers the environmental and nutritional characteristics of more than 2,500 food items consumed in the USA, optimizing diets based on the healthy life gained from the Health Nutritional Index. Aligned with the Paris Agreement’s 1.5 °C target, various diets are found to offer up to 700 min of healthy life gained per week, while reducing climate impacts by a factor of seven. Vegan, vegetarian and flexitarian diets that limit meat consumption to 255 g per week (pork and poultry) best met environmental and nutritional constraints. Grains, legumes and nuts were the primary protein sources. These diets provide a range of specific options for consumers and actionable targets for policy recommendations.
Generated Summary
This research presents a linear programming model designed to identify food combinations that align with environmental and nutritional requirements at an individual level. The study utilized US-specific data, assessing the environmental and nutritional characteristics of over 2,500 food items. It aimed to determine dietary patterns that could meet health targets while operating within planetary boundaries. The model focused on optimizing diets based on the Health Nutritional Index (HENI) and aligned with the 1.5°C target of the Paris Agreement. The study also provided a range of options for consumers and policy recommendations, and included analyses of vegan, vegetarian, and flexitarian diets.
Key Findings & Statistics
- Globally, 700-800 million people suffer from undernutrition, and over 2 billion adults are overweight or obese.
- Approximately 50 and 160 million disability-adjusted life years have been attributed to malnutrition and obesity, respectively.
- Agriculture accounts for around one-quarter of global greenhouse gas emissions, covers 40% of ice-free land areas, consumes 70% of freshwater use, and contributes more than 80% of nitrogen and phosphorus use.
- Vegan, vegetarian, and flexitarian diets that limit meat consumption to 255 g per week (pork and poultry) best met environmental and nutritional constraints.
- Various diets were found to offer up to 700 min of healthy life gained per week while reducing climate impacts by a factor of seven.
- The maximum meat intake that resulted in a feasible solution comprised only three servings of meat (i.e., 255 g) per person per week, limited to pork and poultry.
- The carbon footprint could decrease by a factor of seven, from 35 down to 5 kg CO2 eq cap−1 wk−1 (ranging from factors of 3 to 10 for the other environmental indicators).
- The minimum threshold value for climate change that enabled possible solutions was found to be 0.7 kg CO2 eq cap−1 d−1 or 4.9 kg CO2 eq cap−1 wk−1 (that is, closely aligned with the 1.5 °C target).
- The optimized diets generally contained the highest numbers of servings of grains and vegetables, proposing around 20-40 servings per week of each, followed by nuts, seeds, and fruits (that is, 10-20 servings).
- Meat-free diets show a HENI score of 100-200 min of extra healthy life per week compared with diets that include meats.
- For comparison, in 2021 the meat intakes (excluding seafood) for average European and US citizens were 211 g d−1 and 348 g d−1, respectively (that is, 6–10 times higher than our proposed maximum intake).
Other Important Findings
- The study highlights the possibility of achieving both environmentally sustainable and healthy diets, even when food items such as processed meats are restricted.
- Choosing meats with lower environmental impacts, such as pork instead of beef, is crucial to remain within impact limits.
- The current US diet, with a HENI score close to zero, indicates the need to balance beneficial and harmful foods for better health and environmental sustainability.
- Meat-containing diets seem to be less flexible in terms of achieving a high health score while minimizing climate change impacts, as the impacts of these diets are much higher when not constrained in the model.
- Reducing their climate change impacts seemed to come at the expense of health performance.
- The meat-free diets, however, seem to allow greater flexibility and offer options for pursuing the highest health and sustainability performance.
- The recommended diets exhibit a relatively limited variety of food items.
- The nutritional requirements of various dietary patterns can be met without compromising environmental constraints, suggesting that it is possible to feed everyone with healthy diets.
- A shift from the current average US diet to a diet derived with the model could result in major gains in health and HENI of up to 700 min of healthy life gained each week.
Limitations Noted in the Document
- The model relies on a ceteris paribus principle, considering the impacts of food production based on one year and at a fixed level of consumption.
- Efficiency improvements and other technological gains are important in the transition towards more sustainable food systems and can enhance diet flexibility and contribute to lowering the impacts of products. However, such changes are unlikely to substantially alter the overall conclusions of our study.
- Refining the threshold values could enhance the robustness of the results by strengthening connections between impact indicators and environmental limits.
- The food characteristics are specific to the USA, resulting in diets that reflect US products and environmental intensities.
- The model seeks to select the food items that most easily fulfil the constraints, resulting in solutions with similar food items, even though other items may exist to fulfil the same needs.
- The study did not include impacts from land transformation, nitrogen eutrophication, or chemical toxicity (e.g., from pesticides).
Conclusion
This research demonstrates the potential of various pre-defined dietary patterns to satisfy health and environmental sustainability requirements. It suggests that multiple diets, including those with or without meat, can support both environmental and health objectives. This approach proposes a diverse set of dietary patterns directly at the consumer level, offering individuals a palette of healthy and environmentally sustainable diets from which they can choose. The study’s findings support the feasibility of feeding the US population with healthy diets within planetary limits, emphasizing that meat, particularly red meat, is a limiting factor in achieving sustainable food systems. It indicates the need for substantial reductions in climate change impacts and shifts in dietary habits compared to the current US diet. While meat-free diets offer more flexibility, diets including meat increase the risks of exceeding environmental limits. The study underscores the importance of adopting dietary patterns that include meat with reduced environmental impacts or that are meat-free. The study recommends a shift in dietary guidelines, subsidies, and marketing strategies to emphasize the reduction of red meat consumption and promote foods that support both health and environmental objectives. It advocates for policies that support the transition towards these dietary patterns and food items, emphasizing the need for addressing accessibility and affordability.