Abstract
The Planetary Health Diet (PHD), also known as the EAT-Lancet reference diet, was developed to optimize global dietary quality while keeping the environmental impacts of food production within sustainable planetary boundaries. We calculated current national and global adherence to the PHD using the Planetary Health Dietary Index (PHDI). In addition, we used data on diet and mortality from three large US cohorts (n = 206,404 men and women, 54,536 deaths) to estimate the total and cause-specific mortality among adults 20 y of age and older that could be prevented by shifting from current diets to the reference PHD. The PHDI varied substantially across countries, although adherence was universally far from optimal (mean PHDI = 85 out of 140). By improving the global PHDI to 120, approximately 15 million deaths (27% of total deaths) could be prevented annually. Estimates of preventable deaths due to this shift ranged from 2.5 million for cardiovascular diseases to 0.7 million for neurodegenerative diseases. Our analysis suggests that adopting healthy and sustainable diets would have major direct health benefits by reducing mortality due to multiple diseases and could contribute substantially to achieving the United Nations Sustainable Development Goals. These numbers of preventable deaths are based on evidence that human biology is similar across racial and ethnic groups, but the exact numerical estimates should be interpreted with caution because some assumptions used for the calculations build on limited data. Refinement of these estimates will be possible when additional regional data on diet and mortality become available.
Generated Summary
This research article presents a study on the global adherence to a healthy and sustainable diet, specifically the Planetary Health Diet (PHD), and its potential to reduce premature mortality. The study utilized data from 171 countries/territories and employed a Planetary Health Diet Index (PHDI) to assess dietary quality. Additionally, it analyzed data from three large U.S. cohorts to estimate the association between PHD adherence and mortality. The study’s methodology involved calculating current national and global adherence to the PHD, estimating the total and cause-specific mortality among adults 20 years and older that could be prevented by shifting from current diets to the reference PHD. This approach, distinct from meta-analyses of individual dietary factors, assessed the impact of the PHD on mortality by analyzing repeated dietary assessments within large cohorts to account for the interactions among multiple dietary components. The primary goal was to identify areas needing dietary improvement, guide policymaking, and prioritize public health initiatives. The study aimed to evaluate the potential reduction in the global burden of total and cause-specific mortality achievable with adoption of the PHD by estimating the population attributable fractions (PAFs).
Key Findings & Statistics
- The global mean PHDI score in 2018 was 85 out of a perfect score of 140.
- Among the PHDI components, dairy foods (9.4 out of 10.0), added sugar (8.8 out of 10.0), eggs (8.6 out of 10.0), and poultry (8.3 out of 10.0) received higher scores.
- Added unsaturated fats (3.2 out of 10.0), nuts and seeds (2.6 out of 10.0), non-soy legumes (1.1 out of 5.0), and soybeans/soy foods (0.4 out of 5.0) were among the food groups with the lowest scores.
- The mean PHDI in lower-middle-income countries was the highest (92), while that in low-income countries was lower (79).
- The relatively high PHDI in lower-middle-income countries was attributed to high component scores for whole grains (10.0 out of 10.0), dairy foods (10.0 out of 10.0), red/processed meat (9.6 out of 10.0), poultry (10.0 out of 10.0), eggs (10.0 out of 10.0), and added sugar (9.3 out of 10.0).
- In contrast, while component PHDI scores for low-income countries reflected low intakes of most animal protein sources, the scores also indicated limited consumption of added unsaturated fat and healthy plant-based foods, such as non-starchy vegetables, whole fruits, nuts and seeds, and non-soy legumes.
- Across different geographic regions, the Middle East and North Africa had the highest PHDI of 98, followed by South Asia (93).
- Latin America and the Caribbean (70) and North America (78) showed the lowest PHDI among all the geographic regions.
- Lebanon (102), Tunisia (102), Greece (101), Egypt (100), Libya (100), and Cyprus (99) were among the countries with the highest PHDI.
- Globally, it was estimated that improving dietary quality from the current state to a reference healthy diet with a PHDI of 120 could prevent about 15 million premature deaths among adults per year.
- This accounted for 27% (95% CI: 24%, 30%) of deaths due to all causes in 2019.
- Estimates of preventable deaths: 2.5 million for cardiovascular diseases, 2.0 million for respiratory diseases, 1.6 million for infectious diseases, 1.4 million for cancer, and 0.7 million for neurodegenerative diseases.
- The PAFs were estimated to be: 49% of deaths due to respiratory diseases, 32% of deaths due to neurodegenerative diseases, 22% of deaths due to infectious diseases, 15% of deaths due to cancer, and 14% of deaths due to cardiovascular diseases in 2019.
Other Important Findings
- The PHD emphasizes consumption of vegetables, fruits, whole grains, legumes, nuts, and unsaturated oils; includes modest optional consumption of seafood and poultry; limits consumption of red meat, processed meat, added sugar, salt, refined grains, and starchy vegetables.
- Consistent evidence supports that individuals adhering to the PHD have a lower risk of type 2 diabetes and cardiovascular diseases.
- The PHD, also known as the EAT-Lancet reference diet, has undergone extensive evaluation for its association with noncommunicable disease risks and mortality.
- The PHD index (PHDI) was recently developed and applied to three large cohorts with many repeated dietary assessments.
- The PHDI ranges from 0 to 140, with a minimum score indicating nonadherence to the PHD and a maximum score indicating perfect adherence.
- The study highlights the importance of shifting towards the PHD to reduce the burden of mortality from multiple diseases and to contribute to achieving the United Nations Sustainable Development Goals.
- The study suggests that improving dietary quality shifting toward the PHD is an effective and realistic approach to achieve the third United Nations Sustainable Development Goal (SDG), which targets a one-third reduction of premature mortality from noncommunicable diseases.
Limitations Noted in the Document
- The PHDI was calculated using dietary data based on self-reported intake, which is subject to measurement error.
- The study assumes causality when estimating PAFs based on PHDI scores, though the effects were estimated from observational studies.
- The study populations of the NHS, NHS II, and HPFS consist predominantly of European Americans, limiting the generalizability of the findings.
- The study’s estimates of preventable death estimates are susceptible to additional uncertainties.
- The PHDI may not be optimal for measuring adherence specifically to the PHD.
- The study did not account for the benefits of limiting sodium intake due to limited data on national sodium intakes.
- The potential reduction in mortality for persons under age 20 y that could result from improvements in diet quality was not estimated in the current study.
- The study’s estimates of preventable death estimates are susceptible to additional uncertainties.
Conclusion
The findings of this global study indicate that adherence to the Planetary Health Diet (PHD) varies substantially across countries, with significant implications for public health. The study reveals that the PHD offers a practical and sustainable dietary model. The relatively high PHDI scores in regions consuming the traditional Mediterranean Diet support this view. By improving global dietary quality while maintaining sustainable food production, approximately 15 million premature deaths could be prevented annually. The study’s estimates of the population attributable fraction (PAF) for cause-specific mortality provide valuable insights for public health, particularly in guiding country-specific policymaking. Cardiovascular diseases remain the leading cause of mortality worldwide, and the study found that dietary shifts could have the greatest impact on reducing deaths from these diseases. The research also highlights the potential to alleviate the burden of respiratory and neurodegenerative diseases through dietary improvements. In summary, this research emphasizes the critical need for global adoption of healthy and sustainable diets to reduce premature mortality and protect planetary boundaries. The study’s findings underscore the potential of the PHD as a key strategy for achieving the United Nations Sustainable Development Goals and driving positive change in global health outcomes. Further research and data collection are warranted to refine estimates and tailor interventions to specific regional needs. In conclusion, The study highlights the importance of dietary interventions in achieving the third United Nations Sustainable Development Goal and driving positive change in global health outcomes, underscoring the PHD as a promising approach for reducing mortality and promoting a sustainable food system.