The Planetary Health Diet reduces risk of early death and helps the environment; here's what it entails

One of the healthiest ways to eat also may be most beneficial to the environment, new research shows. 

People who follow the Planetary Health Diet — which emphasizes minimally processed, plant-based foods and allows for modest consumption of meat and dairy — may be lowering their risk of premature death while also limiting their environmental impacts, according to a study published Monday in the American Journal of Clinical Nutrition.

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"Climate change has our planet on track for ecological disaster, and our food system plays a major role," said researcher Walter Willett, a professor of epidemiology and nutrition at Havard's T.H. Chan School of Public Health. "Shifting how we eat can help slow the process of climate change. And what's healthiest for the planet is also healthiest for humans."

The Planetary Health Diet, or PHD, recommends eating plenty of fruits and vegetables, getting protein from plant-based foods like nuts and legumes, and consuming healthy, unsaturated fats – which include foods like avocados, salmon and peanut butter. It also calls for people to decrease their consumption of animal-based protein and added sugars. 

Willett helped develop the diet in 2019 as part of the EAT-Lancet Commission, which set out to improve human health while reducing the environmental impact of feeding the global population.

The latest research – the first large study to focus on the impacts of adhering to PHD – relied on data from 200,000 people who had completed dietary questionnaires every four years for up to 34 years. Harvard researchers measured how closely the participants adhered to the PHD by scoring their diets on the consumption of 15 food groups, including whole grains, vegetables, poultry and nuts. 

How does the PHD impact health?

The participants who most closely adhered to the PHD were 30% less likely to have a premature death than those who followed the diet the least closely. Every major cause of death was lower when more closely following the PHD, including cancer, heart disease and lung disease. The development of neurodegenerative conditions, like Alzheimer's and Parkinson's, also was lower with close adherence.

"It wasn't just one cause of death," Willett told CBC. "It was right across the board."

According to the study, the foods most closely connected to a reduced risk of premature death included whole grains, nuts and health fats like olive oil and sunflower oil. Reducing red meat consumption also was key to decreasing risk. 

How does the PHD impact the environment?

Researchers also found that the people who most closely followed the Planetary Health Diet had a "substantially lower" environmental impact people whose diets were the least in line with the PHD. Their greenhouse gas emissions were 29% lower, their fertilizer needs were 21% lower and their cropland use was 51% less. Reducing the amount of land used is particularly important in aiding re-forestation efforts, which helps decrease the levels of greenhouse gases that drive climate change, researchers said.

Raising livestock for human consumption not only contributes to deforestation and uses up land, but it also contributes to biodiversity loss and water pollution, CNN reported. Further, burps and droppings from cattle, sheep and goats can generate methane, a greenhouse gas that is 80 times more powerful than carbon dioxide in warming the Earth over a span of 20 years. Adult cows generate nearly 15% of the total global greenhouse gas emissions.

"Our study is noteworthy given that the U.S. Department of Agriculture has refused to consider the environmental impacts of dietary choices, and any reference to the environmental effects of diet will not be allowed in the upcoming revision of the U.S. Dietary Guidelines," Willett said in a news release. "The findings show just how linked human and planetary health are. Eating healthfully boosts environmental sustainability – which in turn is essential for the health and wellbeing of every person on earth."