Eat green, live longer: Study finds eco-friendly diets also promote longevity

BOSTON — A more sustainable diet can help you and our planet live longer, according to a new study. A team from Harvard report that those who followed a more environmentally sustainable, planet-friendly diet were 25 percent less likely to die during a follow-up period of over three decades in comparison to others following a less sustainable diet.

These findings build on prior research that identified foods that are a “win-win” for both personal health and the environment. These include whole grains, fruit, non-starchy vegetables, nuts, and unsaturated oils. Meanwhile, there are foods that are potentially harmful to both our planet and human health, notably eggs and red or processed meats. These latest conclusions suggest following a more planet-friendly diet can indeed aid in lowering a person’s risk of death from a host of causes including cancer, heart disease, respiratory diseases, and neurodegenerative diseases.

“We proposed a new diet score that incorporates the best current scientific evidence of food effects on both health and the environment,” says Linh Bui, MD, a PhD candidate in the Department of Nutrition at Harvard T.H. Chan School of Public Health. “The results confirmed our hypothesis that a higher Planetary Health Diet score was associated with a lower risk of mortality.”

Current existing evidence shows that plant-based foods have an association with both a lower risk of chronic diseases such as heart disease, colorectal cancer, diabetes, and stroke, and a minimal impact on the environment when it comes to key considerations such as water use, land use, nutrient pollution, and greenhouse gas emissions.

The aim of this newest project was to create a simple tool policymakers and public health practitioners can use to develop strategies for improving public health and addressing the climate crisis.

“As a millennial, I have always been concerned about mitigating human impacts on the environment,” Bui adds in a media release. “A sustainable dietary pattern should not only be healthy but also consistent within planetary boundaries for greenhouse gas emissions and other environmental parameters.”

To create their Planetary Health Diet Index (PHDI), the research team reviewed existing available research pertaining to the relationships between different food groups and health outcomes based on the EAT-Lancet reference diet that accounts for the environmental impacts of food production practices. Next, they applied the index to analyze outcomes among more than 100,000 participants across two large cohort studies conducted in the United States. That data set encompassed over 47,000 deaths during a follow-up period spanning over three decades between 1986 and 2018.

Generally, this led to the finding that people in the highest quintile (the top one-fifth of participants) for PHDI had a 25-percent lower risk of death from any cause in comparison to those in the lowest quintile. Higher PHDI scores were also associated with a 15-percent lower risk of death from cancer or cardiovascular diseases, a 20-percent lower risk of death from neurodegenerative disease, and a 50-percent lower risk of death from respiratory diseases.

However, Bui cautions that the PHDI does not necessarily reflect all food items and their relationships with all major diseases across all countries. Those with specific health conditions, religious restrictions, or different food accessibility due to socioeconomic status or food availability may face difficulties adhering to more sustainable diet patterns. More research may help better define and address such barriers.

“We hope that researchers can adapt this index to specific food cultures and validate how it is associated with chronic diseases and environmental impacts such as carbon footprint, water footprint, and land use in other populations,” Bui concludes.

This research was presented at NUTRITION 2023, the annual meeting of the American Society for Nutrition.