By Kim Robson:
On the heels of the recent update of the USDA’s dietary guidelines, which promote eating more fruits and veggies, less sugar and salt, and less meat, comes a new study from Carnegie Mellon University, which suggests that growing certain veggies requires more resources per calorie to produce than do pork or chicken products.
The study measured the changes in energy use, blue water footprint, and greenhouse gas (GHG) emissions associated with U.S. food consumption patterns. Contrary to common logic, eating a vegetarian diet could actually contribute to climate change. In fact, following the USDA recommendations to consume more fruits, vegetables and seafood may be more harmful to the environment because those foods require high resource uses and greenhouse gas (GHG) emissions per calorie.
“Eating lettuce is over three times worse in greenhouse gas emissions than eating bacon,” said Paul Fischbeck, professor of Social and Decisions Sciences and Engineering and Public Policy. “Lots of common vegetables require more resources per calorie than you would think. Eggplant, celery, and cucumbers look particularly bad when compared to pork or chicken.”
Fischbeck and his team studied the food supply chain to determine how the obesity epidemic in the U.S. is affecting the environment. Specifically, they examined how growing, processing and transporting food; food sales and service; and household storage and use take a toll on resources in the form of energy use, water use, and GHG emissions.
The results aren’t that simple, however. On one hand, getting our weight under control means eating fewer calories, which has a positive effect on the environment and reduces energy use, water use and GHG emissions from the food supply chain by approximately 9 percent.
On the other hand, eating more of the USDA’s recommended “healthier” foods — fruits, vegetables, dairy and seafood — results in increased environmental impact in all three categories. Energy use went up by 38 percent, water use by 10 percent, and GHG emissions by 6 percent.
“There’s a complex relationship between diet and the environment,” said Michelle Tom, a Ph.D. student in Civil and Environmental Engineering. “What is good for us health-wise isn’t always what’s best for the environment. That’s important for public officials to know and for them to be cognizant of these tradeoffs as they develop or continue to develop dietary guidelines in the future.”
Many experts have blasted the study’s claim as ludicrous. “It is absurd to compare the environmental impacts between bacon and lettuce when you’re using calories as the denominator,” said Brent Kim of the Johns Hopkins Center for a Livable Future’s Food Production and Public Health Program. “A serving of lettuce has fewer calories than a stick of gum.”
It’s not as though vegetarians are going to eat lettuce to make up for the amount of bacon they’re not consuming — and therefore contribute to the associated emissions. Also, to single out lettuce as bad for the planet doesn’t account for the study’s finding that vegetarians might instead consume kale, spinach, potatoes, wheat, and rice — all of which produce fewer emissions than pork does, according to The Huffington Post.
Fischbeck and Tom defended the research: “You can’t lump all vegetables together and say they’re good … You can’t lump all meat together and say they’re bad. My bottom line is that there are no simple answers to complex problems,” Fischbeck told HuffPost. “Diet and the environmental impact of agriculture is not a simple problem.”
Other produce fared better in the Carnegie Mellon study. For instance, cabbage was found to produce only a fifth of the emissions that pork does per calorie, while broccoli generates about half. Meanwhile, beef and lamb produce more emissions than pork or chicken, and beef generates more than lettuce does.
Clear as mud? Personally, I’m going to continue with my ovo-lacto-pescetarian diet, supplemented with the occasional piece of bacon or other meat, but only as a flavor enhancer, never as a main course. I’m a big believer in not demonizing any one food (like salt), but practicing moderation in all things. Next? Tackling my sugar addiction!