Last summer I decided to switch things up and eat vegetarian for a month. I did it for three primary reasons: to improve my health; to sustain myself without the by-products of animal slaughter; and to lessen my environmental impact.

Reason #1 failed, thanks to my own shoddy meal planning. Did you know pierogies are vegetarian? And nachos?

Reason #2 succeeded. I sustained myself without animal flesh, although I still ate eggs and dairy.

Reason #3 I couldn’t prove on my own, but I had always assumed I had lessened my environmental footprint.

As reported by the Washington Post, a new Carnegie Mellon study casts doubts upon the longstanding belief that a vegetarian diet is less harmful to the environment than a diet that contains meat.

The study, published last month in the journal Environment Systems and Decisions, claims that eating more vegetables, fruit, dairy, and seafood is “more harmful to the environment because those foods have relatively high resource uses and greenhouse gas (GHG) emissions per calorie.”

“There’s a complex relationship between diet and the environment,” says Dr. Michelle Tom, one of the researchers behind the study. “What is good for us health-wise isn’t always what’s best for the environment.”

According to the results of the study, a “healthy” diet of fruit, dairy, vegetables and seafood caused energy use to rise by 38 percent, water use to rise by 10 percent, and GHG emissions to rise by 6 percent.

For example, it takes nearly 3 times as much greenhouse gas to produce the same caloric equivalent of head lettuce as it does pork.

“We were very surprised by our results,” CMU reasearcher Paul Fischbeck told the Post. “It’s not what we set out to do – in fact, we expected the exact opposite.”

Behind the splashy “bacon is better for the environment than lettuce” headline, there is the much more complicated issue of how and where our food is produced, and how much of it goes to waste.

Furthermore, this is just one study among many that have studied the issue, many of which have arrived at different results. While some studies seem to confirm the CMU findings, according to the Post, “six other studies, all cited by the federal committee providing expert advice to Dietary Guidelines for Americans, indicated that diets including less meat are better for the environment.”

You can read the full article on the Washington Post website, and an abstract of the study can be found on Springer.

The study was funded by CMU’s Steinbrenner Institute for Environmental Education and Research, and the Colcom Foundation.

Brian Conway

Brian Conway is a writer and photographer whose articles have appeared in the Chicago Tribune and local publications. In his free time, he operates Tripsburgh. Brian lives in the South Side.