Study says lettuce is "three times worse than bacon" in terms of environmental impact

BLT sandwich
CC BY 2.0 Khush N

If you're wanting to reduce your energy use, water footprint, and greenhouse gas emissions, these researchers say that eating a vegetable-based diet may not be the best route to take.

What is best for the body may not be what’s best for the planet. According to a new study published by researchers at Carnegie Mellon University, eating a vegetarian or vegetable-centric diet can actually increase one’s environmental impact in terms of energy use, water footprint, and greenhouse gas emissions. In fact, the researchers state that lettuce is “three times worse than bacon” when it comes to emissions.

The study examined the environmental impact by shifting the average American diet to three dietary scenarios. In the first scenario, researchers reduced the number of calories consumed but maintained the proportion of meat and vegetables consumed, which cut emissions, water and energy use by 9 percent.

In the second scenario, researchers maintained calorie intake but shifted completely to “healthy” foods (as prescribed by USDA dietary guidelines). This increased energy use by 43 percent, water footprint by 16 percent, and emissions by 11 percent.

In the third scenario, calorie intake was reduced and diet was made healthier by drastically reducing meat consumption. The result was 38 percent increased energy use, 10 percent more water, and 6 percent more emissions.

These findings go against the recent call to reduce meat consumption in order to combat climate change. Various studies cite different numbers for the emissions linked to animal agriculture, but some claim it’s as high as 51 percent.

“The experts examined how growing, processing and transporting food; sales and service; and household storage and use all take a toll on the environment for different foods.” (The Independent)

Many common vegetables require far more resources per calorie than you’d think. Says Paul Fischbeck, study co-author and professor of social and decisions science at Carnegie Mellon University, “Eggplant, celery, and cucumbers look particularly bad when compared to pork and chicken.”

Because most vegetables have low ‘calorie density’ compared to meat, you need more of them in order to satisfy hunger and caloric intake. In response to this study, Grist points out that you'd have to eat 93 cups of shredded lettuce in order to equal the number of calories in four pieces of bacon, which is absurd. Nobody would eat that much lettuce, and that's why measuring foods calorie-for-calorie is misleading.

Despite that, it is an interesting study to ponder. It does not separate more sustainable production methods, such as organic and local, from conventional agricultural, nor can it possibly assess shipping accurately since we all live in different places and have different buying habits. Instead it generalizes practices across the United States. It’s true, however, that far more people buy bagged California-grown lettuce mixes than go out to their backyard gardens to snip salad greens for dinner.

An important takeaway point is to understand that both health and environment are impacted by the dietary choices we make, and that’s something that policy-makers need to pay attention to while outlining future dietary guidelines. I guess vegetarian locavores have the best of both worlds!

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