Abstract
The food system is responsible for more than a quarter of all greenhouse gas emissions while unhealthy diets and high body weight are among the greatest contributors to premature mortality. Our study provides a comparative analysis of the health and climate change benefits of global dietary changes for all major world regions. We project that health and climate change benefits will both be greater the lower the fraction of animal-sourced foods in our diets. Three quarters of all benefits occur in developing countries although the per capita impacts of dietary change would be greatest in developed countries. The monetized value of health improvements could be comparable with, and possibly larger than, the environmental benefits of the avoided damages from climate change.
Generated Summary
This research, a region-specific global health model, investigates the health and environmental impacts of dietary changes by linking health outcomes with environmental consequences. The study employs a comparative risk assessment model to estimate age and region-specific mortality associated with changes in dietary and weight-related risk factors, specifically focusing on the consumption of red meat, fruits, vegetables, and the prevalence of overweight or obesity. The research incorporates emissions accounting and economic valuation modules to quantify the health and environmental impacts of dietary changes. Four dietary scenarios were analyzed: a reference scenario (REF) based on FAO projections, a scenario based on global guidelines on healthy eating and energy intake (HGD), and scenarios based on vegetarian (VGT) and vegan (VGN) dietary patterns. The economic valuation involves the value of statistical life (VSL) and the cost-of-illness approach.
Key Findings & Statistics
- The food system is responsible for more than a quarter of all greenhouse gas emissions.
- Unhealthy diets and high body weight are among the greatest contributors to premature mortality.
- Transitioning toward more plant-based diets could reduce global mortality by 6-10% and food-related greenhouse gas emissions by 29-70% compared with a reference scenario in 2050.
- The economic benefits of improving diets could be 1-31 trillion US dollars, which is equivalent to 0.4-13% of global gross domestic product (GDP) in 2050.
- In the HGD scenario, the changes include increasing global fruit and vegetable consumption by 25% (99 g⋅d⁻¹) and decreasing global red meat consumption by 56% (42 g⋅d⁻¹).
- Compared with the reference scenario, we project that adoption of global dietary guidelines (HGD) would result in 5.1 million avoided deaths per year [95% confidence interval (CI), 4.8–5.5 million] and 79 million years of life saved (CI, 75–83 million).
- The equivalent figures for the vegetarian (VGT) diet are 7.3 million avoided deaths (CI, 7.0–7.6 million) and 114 million life years saved (CI, 111–118 million) and for the vegan (VGN) diet 8.1 million avoided deaths (CI, 7.8–8.5 million) and 129 million life years saved (CI, 125–133 million).
- About 45–47% of all avoided deaths were from reduced coronary heart disease (CHD), 26% from stroke, 16–18% from cancer, and 10–12% from type 2 diabetes mellitus (T2DM).
- In the HGD scenario, the changes include increasing global fruit and vegetable consumption by 25% (99 g⋅d⁻¹) and decreasing global red meat consumption by 56% (42 g⋅d⁻¹).
- We project GHG emissions associated with food consumption to increase by 51%, from 7.6 ± 0.1 giga tonnes (Gt)·y⁻¹ in 2005/2007 to 11.4 ± 0.2 Gt-y⁻¹ in 2050.
- Food-related GHG emissions in the HGD scenario were 8.1 ± 0.1 Gt-y⁻¹, which is 29% less than REF emissions in 2050 and 7% greater than emissions in 2005/2007.
- The two vegetarian diets resulted in food-related GHG emissions at midcentury (VGT, 4.2 ± 0.1 Gt-y⁻¹; VEG, 3.4 ± 0.1 Gt-y⁻¹) that were 45–55% lower than the 2005/2007 levels and 63–70% lower than REF emissions.
- Emissions reductions in the HGD scenario were largely attributable to reduced red meat consumption (3.2 ± 0.1 GtCO2, 97%) whereas reductions in red meat (6.1 ± 0.1 GtCO2, 85%) and poultry (1.08 ± 0.01 GtCO2, 15%) were responsible for lower VGT emissions, and lower consumption of red meat (76%), poultry (13%), and eggs and dairy (1.2 ± 0.03 GtCO2, 15%) for lower VGN emissions.
- In relation to an emissions pathway that is believed to be likely to limit global temperature increase to below 2 °C (32), we project that the ratio of food-related GHG emissions to GHG emissions from all sources increases from 16% in 2005/2007 to 52%, 37%, 19%, and 15% in 2050 in the REF, HGD, VGT, and VGN scenarios, respectively.
- For the HGD scenario, we estimate that the monetized value associated with diet-related changes in mortality amount to 21 trillion (or 10¹²) US dollars per year ($21 trillion-y⁻¹) in 2050 with a range of $10-31 trillion y⁻¹. The values we obtain for the VGT diet are $28 trillion-y⁻¹ ($14–42 trillion-y⁻¹), and for the VGN diet $30 trillion-y⁻¹ ($15–46 trillion y⁻¹).
- For the HGD scenario, we estimate that the monetized value associated with diet-related changes in mortality amount to 21 trillion (or 10¹²) US dollars per year ($21 trillion-y⁻¹) in 2050 with a range of $10-31 trillion y⁻¹. The values we obtain for the VGT diet are $28 trillion-y⁻¹ ($14–42 trillion-y⁻¹), and for the VGN diet $30 trillion-y⁻¹ ($15–46 trillion y⁻¹).
- We found that adoption of diets meeting dietary guidelines (HGD) would have monetized environmental benefits of $234 billion y⁻¹, with values in the range $89-729 billion-y-¹ for different assumptions about discount rates.
- The benefits were greater for diets with fewer animal-sourced foods: for VGT, $511 billion-y-¹ ($194-1,589 billion-y⁻¹) and, for VGN, $570 billion y⁻¹ ($217–1,773 billion y⁻¹).
Other Important Findings
- The study shows that reducing red meat consumption, increasing fruit and vegetable intake, and reducing overall energy intake could lead to significant reductions in total mortality.
- The greatest number of avoided deaths occurred in developing countries, particularly in East and South Asia.
- Changes in regional diets significantly impact global GHG emissions.
- Food-related GHG emissions per capita fell twice as much in developed countries compared with developing countries in the HGD and VGT scenarios.
- The economic valuation of health benefits using the cost-of-illness approach showed significant health-related cost savings with the adoption of healthier diets.
- The value-of-statistical-life approach yielded higher estimates of the economic benefits associated with dietary change.
- The economic benefits of reduced GHG emissions were explored using the social cost of carbon.
Limitations Noted in the Document
- The study acknowledges uncertainties related to food demand and mortality projections.
- There are potential deviations from linear dose-response relationships.
- The study’s inability to remove all possible confounding effects when deriving relative risk parameters.
- The health impacts of dietary patterns are inferred from observational studies, which are complicated by multiple confounding factors.
- The study did not assess the market responses associated with dietary changes, such as price changes.
Conclusion
The research underscores the significant benefits of dietary changes towards plant-based diets, emphasizing reductions in mortality and GHG emissions. The study highlights the potential for reducing total mortality by 6-10% and food-related greenhouse gas emissions by 29-70% by 2050. Economic benefits of improving diets could reach 1-31 trillion US dollars. The study underscores the importance of regional variations, with developing countries potentially experiencing the greatest benefits in avoided deaths. The greatest number of avoided deaths (∼72%) occurred in developing countries, in particular in East Asia (31–35%) and South Asia (15–19%). Reducing red meat consumption was the risk factor that had the most positive effect on health in East Asia (78–82%), Western high- and middle-income countries (64–71%; 58–65%), and Latin America (42–48%). Increasing fruit and vegetable consumption was responsible for the majority of avoided deaths in the least developed regions (South Asia, 75–83%; Sub Saharan Africa, 72–84%). Reduced energy intake and the consequent fewer people overweight and obese were particularly important in the Eastern Mediterranean (41–79%), Latin America (32–48%), and Western high- and middle-income countries (29–40%; 20–33%). The study underscores that adopting global dietary guidelines would not be enough to reduce food-related GHG emissions to the same extent that total GHG emissions will need to fall to achieve a climate stabilization pathway. The study suggests that, to achieve climate stabilization, a balance will need to be struck between the degree of adoption of plant-based diets, advances in mitigation technologies of the food sector, and disproportionate reductions in non-food-related GHG emissions.
IFFS Team Summary
- Faunalytics Review: Weighing the Health and Climate Benefits of Eating Less Meat
- Transitioning to a more healthy plant based diet reduce global mortality by 6-10%
- It would decrease global GHG from food by 29-70% , compared to conventional diet
- The positive economic impact of reduced climate change for the future is also considered, and great economic variability exists in this complex domain
- Article was used as a reference for the 2017 Canada food guide process
- The largest absolute environmental and health benefits will be in developing countries
- Western high-income and middle-income countries gain most in per capita benefit
- Specifically compares Healthy Global Diet to Vegetarian and Vegan diets with respect to health and ecological impact
- Also identifies pulses as an ideal plant based protein source
- The Lancet Planetary Health
- https://www.thelancet.com/action/showPdf?pii=S2542-5196%2818%2930206-7
- https://www.thelancet.com/journals/lanplh/article/PIIS2542-5196(18)30206-7/fulltext?dgcid=raven_jbs_etoc_email
- 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
- 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)
- Plant based diets reduce
- GHG emissions by 54–87%
- nitrogen application by 23–25%
- phosphorus application by 18–21%
- cropland use by 8–11% (this statistic does not likely reflect a full switch to pulses)
- freshwater use by 2–11%
- (note that there is regional variation)
- these numbers reflect a shift towards plant foods, but not a full switch from animal protein to pulses
- In developing countries there is a decrease in resource use as more pulses are consumed, while meat is still consumed, but also an increase in resource use as more fruits and vegetables are added to a diet that is subsistence based.
- In developing countries, the environmental impact increases because net food consumption must increase to achieve nutritional targets
- levels of pulses, fruits and vegetables increase dramatically under plant based scenarios
- people in many developing countries have especially low levels of fruit and vegetable consumption,
- (much water is needed to increase)
- to quantify the diverse impact of animal foods in developing countries on biodiversity etc is beyond the scope of this study
- sustainable diets are more context specific and complex depending on local resources
- may involve low levels of animal protein and increased plant foods
- High income countries achieved the largest benefits with respect to health and environment, with incremental plant diet
- Study places emphasis on pulses as the main plant protein, and does specify vegan diets
- Calcium intake may be slightly lower on a vegan diet, and B12 may be absent.
- note that both are easily supplemented