Events & Media

No, Bacon is not Better for the Environment than Lettuce Is
Misleading viral headlines and weird diets: 37 heads of lettuce per day?

By Sangwon Suh
Professor, Bren School of Environmental Science & Management

On Dec. 15, the global media heralded a headline that read: “Eating lettuce is over three times worse in greenhouse gas emissions than eating bacon.”

It got a lot of attention. But the headline, which referred to a newly published study by a group of researchers at Carnegie Mellon University, not only misrepresented the science behind the study, but may also undo years of efforts by scientists around the world intended to help the public make informed dietary choices for the health of humans and the planet.

Sangwon Suh

Interestingly, the peer-reviewed scientific article that the media referred to does not even mention the word “lettuce” or “bacon.” The lettuce-versus-bacon comparison first appeared as an interview statement by Paul Fischbeck, one of the co-authors of the article, in the Carnegie Mellon press release. It was then reproduced virally throughout global media outlets and social networks.

The critical point that the statement does not make clear is that the researchers’ comparison was based on equal calorie counts of lettuce and bacon. To put this into perspective, consider that, on average, lettuce contains about 0.15 calories per gram, while bacon contains about 5.4 calories per gram. Said another way, you would need nearly 30 times as much lettuce as bacon to reach a given calorie count, so a 2,000-calorie daily diet translates to 13 kg (about 29 pounds, or 37 heads) of lettuce versus 0.37 kg (or 0.82 pounds) of bacon.

But who would gobble down 37 heads of lettuce in a day? The comparison misses the point that different foods serve different nutritional purposes in a balanced diet. What is even more unfortunate is that the bacon-lettuce comparison was presented in the global news media and social networks as if it represented the science. It doesn't.

Even the underlying peer-reviewed article that the press release and the media refer to as the source of the statement does not support the claim. The original study compares a number of dietary scenarios, and nowhere did it compare lettuce to bacon. My colleagues and I are preparing a commentary addressing a number of technical issues in the paper, but the study itself is comprehensive and subtle ― and does not address the lettuce-versus-bacon issue that the media focused on.

Study after study has shown that vegetarian, vegan, and Mediterranean diets are better for the environment than meat-intensive diets across a wide range of impacts, including climate change, water consumption, fossil-energy use, and toxic impacts to humans and ecosystems.

For example, a study by the International Resource Panel (IRP) of the United Nations Environmental Programme (UNEP) titled “Assessing the Environmental Impacts of Consumption and Production” identifies meat and dairy products as a major source of negative environmental impacts. A study by the US Environmental Protection Agency, “Sustainable Materials Management: The Road Ahead,” ranks animal products as one of the categories that most significantly and adversely affect the environment. And in the journal Energy Policy, a study titled “The relative greenhouse gas impacts of realistic dietary choices” concludes that going vegetarian or vegan reduces GHG emissions by 22 percent and 26 percent, respectively. A study published in Nature, “Global diets link environmental sustainability and human health,” also highlights the global environmental benefits of vegetable-rich and Mediterranean diets.

This does not mean that all vegetables (or all varieties of meat, for that matter) are created equal. Some vegetables are more chemical- or water-intensive to grow than others, and vegetables grown in or near sensitive ecosystems or where water is scarce are certainly more burdensome to the environment. Likewise, the environmental impacts of meat-oriented diets can vary widely depending on, among other factors, the type of meat and the location of feed sources.

Accounting for such details does matter and requires a sophisticated strategy for collecting and analyzing data and communicating the scientific results to consumers. Despite such variabilities, the literature strongly and consistently favors reasonable (not 37 heads of lettuce per day!) vegetable-rich diets over meat-rich diets from an environmental perspective.

So yes, you can and should keep vegetables in your diet ― to support your own health and the planet’s, too.