It's a message that's been repeated by animal rights groups like PETA, environmental organizations like the David Suzuki Foundation, and even the United Nations — the most environmentally-friendly diet choice you can make is eating less meat, if not an entirely vegetarian diet.
Which is why a newly-published study raised a lot of eyebrows, and generated headlines proclaiming that vegetarian diets might actually be harmful to the environment.
As it turns out, though, those headlines weren't quite capturing the real story.
The common argument has been that diets lower in meat can reduce greenhouse gas emissions and, if enough of us do it, we could put a dent in the meat industry and reduce climate change.
CBC Radio's the Current recently hosted a panel that made that argument.
Water-guzzling beef
"Meat is having a really major impact on our environment," according to panelist Laura Wellesley. She's the co-author of a report from the British think-tank Chatham House, called Changing Climate, Changing Diets: Pathways to Lower Meat Consumption.
Simple rules like 'go vegetarian and you'll reduce your footprint' can certainly be true, but are not always true. - Paul Fischbeck, study co-author
"A large share of the emissions — about two-thirds of the emissions — come from the livestock themselves, so their digestive processes and also their manure," she told the Current.
"And around a further sixth comes from the production of crops for animal feed. And of course, you have carbon dioxide emissions as well from the transportation of animal products, heating and cooling of buildings, use of machinery, etcetera."
Beef, she said, is particularly notorious for being environmentally unfriendly. According to a report from the London-based Institution of Mechanical Engineers, it takes more than 15,000 litres of water to produce a kilogram of beef, thanks in part to the water-heavy alfalfa and forage used to raise cows.
Lettuce vs. bacon
Hence the surprise when Carnegie Mellon University researchers published a study with a seemingly contrarian conclusion.
The university even put out a news release with an attention-grabbing headline that said "Eating Lettuce Is More Than Three Times Worse in Greenhouse Gas Emissions Than Eating Bacon."
Lettuce 'happens to have a relatively large impact on the environment,' says Carnegie Mellon University's Paul Fischbeck. (Getty Images)
Paul Fischbeck is a professor of engineering and public policy at Carnegie Mellon, and was one of the study's authors. And he says the headline is accurate — but not the entire story.
"Lettuce is a relatively fragile vegetable. It requires lots of water to grow," he said.
"It's not very dense. And so you get a truckload of lettuce, it doesn't weigh very much, but you still have to drive that truck. It has to get to the market relatively quickly, it has to get home, there's a lot of food loss along the way. And so if you look at the farm-to-fork analysis, lettuce happens to have a relatively large impact on the environment."
Not all vegetables created equal
But that's not the only point that Fischbeck and his co-authors make in their study, which points out that not all vegetables are created equal.
Fischbeck said he doesn't doubt that beans, nuts, and seeds are highly efficient and sustainable foods. But lettuce, for example, is not — nor are water-rich foods like eggplant, cucumber, and celery.
To explain, Fischbeck's study compares calories. If you were to replace, say, 100 calories of bacon — about two pieces — with 100 calories of cucumber, you'd need to eat more than six cups of the vegetable to get the same number of calories as you would through the bacon.
A slice of bacon provides about 50 calories. You'd need to eat more than three cups of sliced cucumbers for the same calorie intake. (Jennifer Quesnel/CBC)
That's why on paper, replacing bacon calorie-for-calorie with vegetables like lettuce or cucumbers would be highly inefficient — simply because it would lead to the production and shipping of massive volumes of produce.
"Simple rules like 'go vegetarian and you'll reduce your footprint' can certainly be true, but are not always true," Fischbeck said.
"Is it better to have a simple message that may in fact be less accurate, or to have a more nuanced message that is in fact more accurate? This is a classic problem when it comes to communication of information to the public."
And on the subject of nuance, Fischbeck says the news coverage of his study didn't have a lot. Some of the headlines on stories about the research might have lead to the belief that a bacon-rich diet could save the planet.
It won't, so don't try, according to Fischbeck, who says such headlines make for grabby journalism, but bad communication.
Khalil Akhtar is a syndicated food columnist with CBC Radio.
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