Abstract
Background Sustainable diets are intended to address the increasing health and environmental concerns related to food production and consumption. Although many candidates for sustainable diets have emerged, a consistent and joint environmental and health analysis of these diets has not been done at a regional level. Using an integrated health and environmental modelling framework for more than 150 countries, we examined three different approaches to sustainable diets motivated by environmental, food security, and public health objectives. Methods In this global modelling analysis, we combined analyses of nutrient levels, diet-related and weight-related chronic disease mortality, and environmental impacts for more than 150 countries in three sets of diet scenarios. The first set, based on environmental objectives, replaced 25–100% of animal-source foods with plant-based foods. The second set, based on food security objectives, reduced levels of underweight, overweight, and obesity by 25–100%. The third set, based on public health objectives, consisted of four energy-balanced dietary patterns: flexitarian, pescatarian, vegetarian, and vegan. In the nutrient analysis, we calculated nutrient intake and changes in adequacy based on international recommendations and a global dataset of nutrient content and supply. In the health analysis, we estimated changes in mortality using a comparative risk assessment with nine diet and weight-related risk factors. In the environmental analysis, we combined country-specific and food group-specific footprints for greenhouse gas emissions, cropland use, freshwater use, nitrogen application, and phosphorus application to analyse the relationship between the health and environmental impacts of dietary change. Findings Following environmental objectives by replacing animal-source foods with plant-based ones was particularly effective in high-income countries for improving nutrient levels, lowering premature mortality (reduction of up to 12% [95% CI 10–13] with complete replacement), and reducing some environmental impacts, in particular greenhouse gas emissions (reductions of up to 84%). However, it also increased freshwater use (increases of up to 16%) and had little effectiveness in countries with low or moderate consumption of animal-source foods. Following food-security objectives by reducing underweight and overweight led to similar reductions in premature mortality (reduction of up to 10% [95% CI 9–11]), and moderately improved nutrient levels. However, it led to only small reductions in environmental impacts at the global level (all impacts changed by <15%), with reduced impacts in high-income and middle-income countries, and increased resource use in low-income countries. Following public health objectives by adopting energy-balanced, low-meat dietary patterns that are in line with available evidence on healthy eating led to an adequate nutrient supply for most nutrients, and large reductions in premature mortality (reduction of 19% [95% CI 18–20] for the flexitarian diet to 22% [18–24] for the vegan diet). It also markedly reduced environmental impacts globally (reducing greenhouse gas emissions by 54–87%, nitrogen application by 23–25%, phosphorus application by 18–21%, cropland use by 8–11%, and freshwater use by 2–11%) and in most regions, except for some environmental domains (cropland use, freshwater use, and phosphorus application) in low-income countries. Interpretation Approaches for sustainable diets are context specific and can result in concurrent reductions in environmental and health impacts globally and in most regions, particularly in high-income and middle-income countries, but they can also increase resource use in low-income countries when diets diversify. A public health strategy focused on improving energy balance and dietary changes towards predominantly plant-based diets that are in line with evidence on healthy eating is a suitable approach for sustainable diets. Updating national dietary guidelines to reflect the latest evidence on healthy eating can by itself be important for improving health and reducing environmental impacts and can complement broader and more explicit criteria of sustainability.
Generated Summary
This study employs an integrated health and environmental modeling framework across more than 150 countries to assess the impacts of various sustainable diet strategies. It examines three distinct approaches: reducing animal-source foods, improving food security by addressing energy imbalances, and implementing public health objectives through balanced dietary patterns. The analysis integrates nutrient levels, diet-related and weight-related chronic disease mortality, and environmental impacts, providing a comprehensive view of how dietary changes influence health and the environment. The research utilizes a comparative risk assessment, assessing mortality changes based on nine dietary and weight-related risk factors. The environmental analysis incorporates country-specific data for greenhouse gas emissions, cropland use, freshwater use, nitrogen application, and phosphorus application to evaluate the relationships between health and environmental impacts. This approach allows for a detailed evaluation of the health and environmental implications of different dietary scenarios across various regions.
Key Findings & Statistics
- The first set of scenarios, focusing on environmental objectives, involved replacing animal-source foods with plant-based alternatives. Complete replacement (ani-100) in high-income countries could lead to a 12% reduction (95% CI 10–13) in premature mortality.
- However, the same scenario increased freshwater use by up to 16%.
- The second set addressed food security, and reducing underweight and overweight led to a 10% reduction (95% CI 9–11) in premature mortality.
- The third set focused on public health objectives, implementing balanced, low-meat dietary patterns, yielding substantial reductions in premature mortality: the flexitarian diet reduced mortality by 19% (95% CI 18–20), while the vegan diet achieved a 22% reduction (95% CI 18–24).
- Adopting a balanced diet also led to large reductions in environmental impacts globally, including a 54–87% reduction in greenhouse gas emissions, 23–25% in nitrogen application, 18–21% in phosphorus application, 8–11% in cropland use, and 2–11% in freshwater use.
- The study found that in low-income countries, approaches that diversify diets could increase resource use.
- The research indicates that a diet with a high reduction of meat and a high inclusion of fruits, vegetables, legumes, and nuts reduces premature mortality.
- The reductions in premature mortality were two to three times greater in high-income and middle-income countries (12-14% in the ani-100 scenario), where a larger portion of animal-source foods can be substituted, than in low-income countries (5%; figure 3).
- The scenarios focused on improving energy balance (kcal-25, kcal-50, kcal-75, and kcal-100), total energy intake was reduced to achieve recommended values in high-income and middle-income countries, whereas it was increased to achieve recommendations in low-income countries (appendix p 27).
- Across risk factors, reductions in obesity contributed the most to the overall reduction in premature mortality (61-65% across the scenarios), followed by reductions in underweight (42-43%) and reductions in overweight (excluding obesity; 15–17%).
- Globally, moving to the balanced dietary patterns resulted in large reductions in greenhouse gas emissions (54–87% across the scenarios), medium-level reductions in nitrogen application (23–25%) and phosphorus application (18–21%), and small to moderate reductions in cropland (8–11%) and freshwater use (2–11%).
Other Important Findings
- The study highlights that public health strategies focused on balanced, predominantly plant-based diets are more effective in reducing environmental pressures, preventing nutrient deficiencies, and decreasing diet-related mortality compared to approaches focused solely on environmental or food security goals.
- The study suggests that updating national dietary guidelines to reflect the latest evidence on healthy eating can be a crucial step in improving health and environmental sustainability, complementing broader sustainability criteria.
- The study emphasizes that the health and environmental impacts of dietary changes vary significantly across regions and environmental domains.
- The study found that progressively replacing animal products with plant-based foods led to large reductions in greenhouse gas emissions (from 20% in the ani-25 scenario to 84% in the ani-100 scenario).
- The study found that the flexitarian, pescatarian, vegetarian, and vegan diets led to the greatest alignment of health and environmental impacts.
- The study noted that increases in nut consumption in the four scenarios led to reductions in premature mortality.
Limitations Noted in the Document
- The study acknowledges that its analysis did not incorporate all aspects relevant to sustainable diets, such as biodiversity impacts and economic factors.
- The study notes that the mortality estimates are based on changes in dietary risk factors in equilibrium and may not fully capture real-world complexities, such as the time lag between dietary changes and mortality changes.
- The study’s reliance on food-availability data might limit the inclusion of certain risk factors, such as processed meat and whole grains, which could affect the estimated benefits of dietary changes.
- The study acknowledges that the environmental assessment relies on current country-level data, and scenario changes are in line with other assessments with similar detail.
- The study recognizes that regional differences in yields, water use, and fertilization intensity lead to variations in environmental impacts.
Conclusion
The research emphasizes that sustainable diets must balance health, environmental considerations, and regional contexts. Public health approaches emphasizing balanced, plant-based diets show the most promise in reducing environmental pressures, nutrient deficiencies, and diet-related mortality. The study underscores the importance of updating national dietary guidelines to align with current evidence on healthy eating, which can contribute significantly to sustainability. The study’s findings highlight the regional variability in the health and environmental impacts of dietary changes, emphasizing that environmental and health benefits can be greatest when considering a global perspective, while also focusing on region-specific strategies. The success of such strategies depends on combining technological, dietary, and management innovations. The balanced dietary patterns such as flexitarian, pescatarian, vegetarian, and vegan diets, demonstrate the greatest potential for aligning health and environmental improvements, particularly in high-income countries. The research suggests that in low-income countries, dietary changes must be coupled with improvements in food production and distribution to prevent increased resource use. The results suggest that environmental concerns should be addressed, especially by reducing animal-source foods, while also acknowledging the challenges of increased freshwater use. The analysis also finds that approaches focused solely on environmental or food security goals may not achieve the same level of health and environmental benefits as public health-focused strategies. Ultimately, the study advocates for the development of food-based dietary guidelines that take into account both dietary composition and energy balance to enhance health and environmental outcomes. This comprehensive approach can improve public health and reduce environmental impacts.
IFFS Team Summary
- Models at sustainable diets globally, in the context 150 low, middle and high income countries, and the relative ecological impact
- Uses a standard nutritional profile for incremental levels of meat reduction, health prevention, as well as semi veg, veg, and vegan diets
- i.e. each diet must attain certain level of calories, protein, and micronutrients
- i.e. each diet must attain certain level of calories, protein, and micronutrients
- Diets that were the most plant based, especially vegan achieved the most ecological benefits AND greatest health benefits
- “ Flexitarians ” reduce premature mortality by 19%, and vegans by 21% (the document actually mentions vegans)
- See FULL ENTRY in the Food Security Reference List for Animal Agriculture Ecology and Food Security list
- more ecological information is given there
- more ecological information is given there