This Is the Best Diet to Save the Planet

The vegan diet is often lauded as the most environmentally friend way to eat, but scientists have highlighted that cutting down on animal products can also help to protect the planet against climate change.

A worldwide move towards plant-focused diets is "essential for meeting climate change mitigation targets," scientists wrote in the journal Global Environmental Change. But how this is achieved depends on the country.

The team, from Johns Hopkins University, Maryland, looked at the carbon and water footprints of nine plant-rich diets from 140 countries, and compared them with what is typically eaten. A total of 74 food items were considered.

What are known as ruminant meats—such as cattle, sheep, and goat—had "by far" the biggest greenhouse gas footprint, with 6.54 kg (14.4 pounds) of bovine meat some 316 times more greenhouse gas intensive than pulses. Plant foods were the least intensive, on average.

In 97 percent of countries, vegan diets had the lowest per capita greenhouse gas footprint. And if all countries adopted this plant-only diet, the amount of greenhouse gases released due to food production would drop by 70 percent per person, the team concluded.

As dairy production pumps out a relatively high level of greenhouse gases, diets involving one animal product for one meal per day was more sustainable than a lacto-ovo vegetarian diet, which cuts out all fish and meat, but includes dairy products.

In 64 percent of the countries studied, diets that excluded dairy had a lower greenhouse gas footprint than vegetarian diets including eggs and dairy products.

In most countries, the two-thirds vegan diet—where two out of three meals per day are based entirely on plants—was less greenhouse gas intensive than a vegetarian diet packed with dairy and eggs.

Meanwhile, diets that were high in plant foods, but that also feature animals low down in the food chain—like foraging fish, mollusks, and insects—also had relatively small water and greenhouse gas footprints, comparable to the vegan diet.

"These findings suggest populations could do far more to reduce their climate impact by eating mostly plants with a modest amount of low-impact meat than by eliminating meat entirely and replacing a large share of the meat's protein and calories with dairy," the authors wrote.

Keeve Nachman, assistant professor in the department of Environmental Health and Engineering at Johns Hopkins University and co-author of the study, told Newsweek one of the most "striking" findings was that people in low and middle income countries will need to eat more animal products to reduce hunger and developmental problems. As a result, people in high income countries will have to make "ambitious changes" to their diets to reduce their environmental impact.

Nachman acknowledged the team did not take into account the processing, transportation, retail and preparation of the diets—but he argued the "bulk of the greenhouse gas emissions are thought to occur in the farming and production stage so this would not make a lot of difference."

Asked what the average American person should be eating if they would like to help tackle climate change, he said the paper shows they could make a "significant difference" to their greenhouse gas and freshwater footprint if they cut down on how many animal products they eat.

That might include one meatless day a week, which would cut the average person's greenhouse gas emissions by 156 pounds a year. Nacham said this is the equivalent to reducing annual mileage in a typical U.S. passenger vehicle by 174 miles.

"If the entire population of the U.S. cut out meat one day a week, that would save more than a trillion liters of water per year—equivalent to 43 percent of the water used to irrigate golf courses across the U.S. each year," he said.

The study is the latest to point to a plant-based diet as the most environmentally friendly. However, the lifestyle is also thought to provide health benefits.

A study published in the journal Science last year mirrored these findings, concluding that cutting down on animal products by half worldwide and not buying from high-impact producers would achieve a 73 percent reduction in emissions of an entirely plant-based diet.

Lessening the consumption of oils, refined sugar, stimulants, and alcohol by a fifth would slash greenhouse gas emissions created by these products by 43 percent.

"As an individual, you can have that impact today—not 20, 50 or 100 years into the future when it might be too late," Oxford University's Joseph Poore, co author of Science study, told Newsweek at the time.

Meanwhile, a study published last week linked vegetarian, vegan and pescetarian diets to a lower risk of coronary heart disease. But vegetarians and vegans were found to be likely to have strokes than meat eaters.

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Researchers have looked at the greenhouse gas and water footprints of plant-forward diets across 140 countries. This stock image shows people gathered around a dining table. Getty
This story is part of a Covering Climate Now project from the Columbia Journalism Review.