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If you follow the intersection of food and climate change, you know that you can barely swing a reusable grocery bag these days without running into a new study or article bemoaning the environmental damages of a meat-heavy diet. So imagine the joy that must have leapt into meat-eaters’ hearts when Tuesday, media outlets from around the world ran a story claiming that the environmental villain lurking in your refrigerator is not that salty slab of bacon, but that crisp head of lettuce hiding innocently in the salad drawer. “Bacon lovers of the world, rejoice!” cried one article in Climatewire. That celebration, however, should be short-lived. Sorry to break it to you, meat enthusiasts, but bacon isn’t necessarily better for the environment than lettuce. The issue is that the Carnegie Mellon study on which the claim was based looked at energy, water use, and greenhouse gas emissions on a per calorie basis. Comparing lettuce to bacon is taking a high-calorie meat and comparing it with a low-calorie vegetable — it’s an unfair comparison. In order to equal the calories in two and a half strips of bacon, you would have to eat an entire head of lettuce. Since you have to eat more lettuce to equal the calories of bacon, you have to first grow more lettuce — and that lettuce is going to use more resources like water and energy. “You’d have to eat a lot of lettuce to get up to a significant amount of calories,” Paul Fischbeck, lead author of the study, told ThinkProgress. On a calorie by calorie basis, lettuce might be worse for the environment than bacon — three times worse, according to the study. By weight, however, pork accounts for six times more greenhouse gas emissions than lettuce. “It is absurd to compare the environmental impacts between bacon and lettuce when you’re using calories as the denominator,” Brent Kim, program officer for the Johns Hopkins Center for a Livable Future’s Food Production and Public Health Program, told ThinkProgress. “A serving of lettuce has fewer calories than a stick of gum.” Foods like fruits and vegetables tend to be much lower in calories than meats, grains, and legumes. That’s why people don’t get the majority of their daily calories from fruits and vegetables — they turn to them for nutrients and vitamins, while seeking calories elsewhere. And that’s why comparing the environmental impact of different foods based on their calorie content can be a little misleading — it’s not as if people cutting 400 calories worth of bacon out of their diet are going to supplement that with 400 calories worth of lettuce (or approximately four heads of Romaine). “Ultimately, just as you wouldn’t sensibly compare lettuce with bacon from a nutritional perspective, comparing them on an environmental perspective is misleading,” Martin Heller, a research specialist with the Center for Sustainable Systems at the University of Michigan, told ThinkProgress over email. “Really, what you need to look at is how they contribute to an overall diet.” Bacon and lettuce conundrum aside, that’s what the Carnegie Mellon study actually did. It set out to answer how shifting our current diets — which tend to be high in calories, red meats, and grains and low in fruits and vegetables — to a USDA recommended diet, which is higher in fruits, vegetables, and meats like poultry and seafood, would impact energy use, greenhouse gas emissions, and water use. “The study compares typical diets to USDA dietary recommendations, which are not sustainable,” Kim said. “For the typical American, following those recommendations would mean eating more seafood and much, much more diary, both of which have a larger environmental footprint.” And that’s basically what the Carnegie study confirmed, finding that the USDA recommended diet — with its emphasis on fruits, vegetables, and seafood — had higher emissions, energy use, and water use than current diets: farm energy increased by 38 percent, and greenhouse gas emissions by 6 percent. That, Fischbeck said, was a “big surprise.” But again, consider the issue of calories. In bumping up the fruits and vegetables of an average diet to meet the USDA recommendations, Fischbeck and his colleague relied on consumers’ current preferences for fruits and vegetables, prioritizing things that Americans tend to eat a lot of, like cucumbers, celery, bell peppers, and tomatoes — all things that tend to be pretty low in calories. The study did not look at how changing fruit and vegetable preferences to things that are both higher in calories and lower in emissions — convincing Americans to eat more cabbage or beans, instead of celery and tomatoes — would impact the environment. “If you redistribute what people prefer about vegetables, you could indeed get different results,” Fischbeck said. “We’re not saying that any vegetarian diet is worse than eating bacon. What we’re saying is that based on the preferences we have, those tend to be, on average, more intensive than the pork products.” The study didn’t look at a vegetarian diet — just a diet as recommended by the USDA, which includes eating less meat, but more seafood and diary. But studies that have looked at vegetarian diets have found that “the more vegetarian you go, the lower your greenhouse gas emissions are going to be,” according to Kim. “In general, no matter what denominator you use, the emissions from plant-based foods are going to be lower, and this study is consistent with that,” he added. The Carnegie Mellon study isn’t wrong — if Americans were to reduce their meat consumption and supplement those lost calories with things like low-calorie fruits and vegetables or seafood and dairy, any decrease in emissions from reduced meat consumption could be offset by increased emissions elsewhere. But that doesn’t change the fact that meat production — especially inefficient meat, like beef — has detrimental impacts on the environment; even the Carnegie Mellon study says that “meats and fish/seafood have the highest average GHG emissions” of any of the food groups looked at. The answer isn’t replacing all of the calories that we would get from meat with low-calorie options like lettuce or celery, or high-emissions alternatives like dairy and seafood. It’s finding more efficient alternatives. That can mean switching to vegetables like squash or cabbage, or prioritizing more efficient meat, like chicken.
