Can a planet-friendly diet reduce your risk of dying from disease?

A diet that promotes plant-based protein now has a more humane argument for helping the environment: It could reduce your risk of dying from some major diseases.

“It was just one cause of death. It was across the board,” said Walter Willett, a professor of epidemiology and nutrition at the Harvard TH Chan School of Public Health.

Willett co-authored a new study that looked at the Planetary Health Diet (PHD) – which he helped develop in 2019 as part of the EAT-Lancet Commission – and its effects on mortality. The diet advises eating plant-based proteins such as nuts and legumes, more fruit and vegetables as well as healthy unsaturated fats – and reducing animal-based protein sources and added sugars.

The new study, published in the peer-reviewed American Journal of Clinical Nutrition, looked at decades of dietary data from more than 200,000 health care workers in the United States. It scored how closely the participants’ eating habits compared to the Planetary Health Diet. The closer they ate to the PHD – for example, eating more nuts and less red meat – the greater the benefit.

“All major causes of mortality were lower,” Willett said, “Including heart disease, cancer, neurodegenerative conditions such as Alzheimer’s disease, Parkinson’s disease and a strong benefit for [respiratory] mortality.”

Willett also noted that the top 10 percent of participants who followed the diet saw a 30 percent lower risk of death from all causes.

The death data was obtained from more than 54,000 participants who died during the study period.

Specific foods were associated with a lower risk

Kathryn Bradbury, a senior research fellow in the School of Population Health at the University of Auckland, called the research comprehensive, and said it involved external factors.

“They also looked at other things that the people were doing in terms of their exercise and their smoking habits,” says Bradbury, who was not involved in the study. She highlighted the specific foods in the study that had a greater impact.

“If you ate a lot of whole grains, a lot of nuts and a lot of healthy fats like olive oil and sunflower oil,” Bradbury told CBC News from Auckland, “the most important things for your reduce risk of death.”

She added that red meat reduction was also important in their analysis.

Three sample plates from the EAT-Lancet Commission’s Planetary Health Diet, showing more plant-based protein sources, more vegetables and whole grains. (EAT-Lancet Commission)

Make a change

For Toronto-based chef, author and food activist Joshna Maharaj, the study is clear and important.

“It’s a beautiful, basic, basic wisdom,” Maharaj said, trying to give more academic support to what sustainability advocates have long talked about.

But she stresses that this isn’t just about cutting back on certain foods like red meat – it’s about growing food more organically.

“There is an ecological way to eat meat,” Maharaj said. “You can eat less of it and pay more for it, but raising and eating animals can be part of a system that works.”

Maharaj says that current industrial meat production is taxing on the environment, through the chemicals used and the land used to support factory farming.

Farmers market or big box grocery chain? Guess the origin of these food items

Can you tell the difference between a local product and a grocery store import? Test your food knowledge with Samira Mohyeddin, host of the CBC Radio series Unforked, and Toronto chef and author Joshna Maharaj.

She says Canadians who want to make a change can start by looking in their fridge and learning about their own consumption patterns.

“Don’t worry about making a magical change,” said Maharaj.

Plates and policies

The good news for Canada is that the country’s revised food guide in 2019 already encourages more plant-based proteins as well as limiting processed foods and sugary drinks.

“Canada’s food guide is largely consistent with a sustainable dietary pattern,” says Benoît Lamarche, scientific director of Laval University’s NUTRSS center, and author of a recent paper comparing the guide to the PHD.

An example of a healthy plate from Canada's food guide.  Half the plate is fruit and vegetables, a quarter is whole grains and a quarter is proteins.
An example of an ideal, healthy plate from Canada’s food guide. (Canada’s Food Guide (2019))

But there is still a challenge in how to communicate an ideal plate of food to people. For example, Canada’s food guide shows a neat quadrant focused on general proteins, telling people how much versus what types of protein.

“We need protein, but total protein is not a good indicator of how healthy we are eating,” Lamarche said. “The source of the protein is a better marker of our diet quality.”

Beyond eating healthy food, a sustainable diet must consider affordability, cultural relevance and whether it’s really good for the environment, Lamarche said.

Can diet really save the planet?

​​​​The new study also found that following the PHD had a lower environmental impact, based on calculations that foods in this diet would emit less greenhouse gases, use less water, fertilizers and top of land required.

“That’s huge,” Willett told CBC News from Cambridge, Mass., “because it really means we could let some of our cultivated land go back to forest … which would definitely help the situation stabilize global climate.”

Cattle graze on a sunny day in a field near Toscare, New South Wales, Australia, November 19, 2023.
Cattle graze in a field near Toscaire, New South Wales, Australia, in November 2023. (Peter Hobson/Reuters)

Climate change, driven largely by the burning of fossil fuels, is also exacerbated by agricultural emissions, including methane, a short-lived and more potent greenhouse gas. A negative feedback loop occurs as food production is then threatened by drought and other extreme weather events, reinforcing and contributing to climate change.

According to Our World in Data’s analysis of UN figures, an estimated 80 percent of the planet’s agricultural land is used for grazing and livestock feeding.

“If, on a population level, everyone reduced their intake of animal-sourced foods,” said Bradbury, “It would be much more effective, because we want to be using that land to grow directly crops of plants that we ate.”

Willett says there is an urgent need to address the impact of our food on the climate.

“It’s scary and it’s unique because it’s not linear, it’s accelerating. And we’re hitting tipping points that will be irreversible.”

Leave a Reply

Your email address will not be published. Required fields are marked *