by For immediate release: June 10, 2024
Boston, MA—People who eat a healthy, sustainable diet may significantly reduce their risk of premature death in addition to their impact on the environment, according to a new study led by Harvard School of Public Health TH Chan. This is the first major study to directly evaluate the impacts of adherence to recommendations in the landmark 2019 EAT-Lancet report. The researchers named the dietary pattern outlined in the report – which emphasizes a variety of lightly processed plant foods but allows moderate consumption of meat and dairy foods – the Planetary Health Diet (PHD).
The study was published online June 10 in The American Journal of Clinical Nutrition.
“Climate change is on our planet’s path to ecological disaster, and our food system plays a major role,” said corresponding author Walter Willett, professor of epidemiology and nutrition. “Changing the way we eat can slow down the process of climate change. And what is healthiest for the planet is also healthiest for people.”
Although other studies have found that diets emphasizing plant-based foods over animal-based foods may have benefits for human health and the health of the planet, most have used one-time dietary assessments, which gives weaker results than looking at diets over a long period of time.
The researchers used health data from more than 200,000 women and men enrolled in the Nurses’ Health Study I and II and the Health Professionals Follow-up Study. The participants were free of major chronic diseases at the start of the study and completed dietary questionnaires every four years for up to 34 years. Participants’ diets were scored based on intake of 15 food groups – including whole grains, vegetables, poultry and nuts – to quantify adherence to the PHD.
The study found that the risk of premature death was 30% lower in the 10% of participants who most closely adhered to PHD compared to those in the lowest 10%. All major causes of death, including cancer, heart disease, and lung disease, were lower when more people adhered to this dietary pattern.
In addition, the researchers found that those with the highest adherence to the PHD had a significantly lower environmental impact than those with the lowest adherence, including 29% less gas emissions lower greenhouse, 21% lower fertilizer requirements, and 51% lower crop land use.
The researchers noted that reducing land use is particularly important as a facilitator of reforestation, which is seen as an effective way to further reduce the levels of greenhouse gases that are driving climate change.
“Our study is noteworthy since the US Department of Agriculture has refused to consider the environmental impacts of dietary choices, and will not allow any mention of the environmental effects of diet in the upcoming revision of the US Dietary Guidelines, ” said Willett. “The results show how linked human and planetary health are. Eating healthily promotes environmental sustainability – which is essential to the health and well-being of everyone on earth.”
Other Harvard Chan School authors included Linh Bui, Fenglei Wang, Qi Sun, Frank Hu, Kyu Ha Lee, and Marta Guasch-Ferre.
The study was funded by National Institutes of Health (NIH) research grants UM1 CA186107, P01 CA87969, R01 HL034594, U01 CA176726, U01 CA167552, R01 HL035464, R01 DK120870, and R06870.
“Planetary Health Dietary Index and risk of total and cause-specific mortality in three prospective cohorts,” Linh P. Bui, Tung T. Pham, Fenglei Wang, Boyang Chai, Qi Sun, Frank B. Hu, Kyu Ha Lee , Marta Guasch-Ferre, Walter C. Willett, The American Journal of Clinical Nutrition, June 10, 2024, doi: 10.1016/j.ajcnut.2024.03.019
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image: iStock/udra
For more information:
Maya Brownstein
mbrownstein@hsph.harvard.edu
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The Harvard TH Chan School of Public Health brings together dedicated experts from many disciplines to educate a new generation of global health leaders and produce powerful ideas that improve the lives and health of people everywhere. As a leading community of scientists, educators and students, we work together to take innovative ideas from the laboratory to people’s lives – not only to make scientific progress, but also to work to shape individual behaviour, public policy and health care practices to change. Each year, more than 400 faculty members at the Harvard Chan School teach more than 1,000 full-time students from around the world and train thousands more through executive and online education courses. Founded in 1913 as the Harvard-MIT School of Health Officers, the School is recognized as America’s oldest professional training program in public health.
