After investigating the way foods are grown, transported and processed, a student-professor at Carnegie Mellon University (CMU) has concluded that if you follow the U.S. Department of Agriculture (USDS) guidelines for healthy eating, you may be doing more harm to the environment than if you ate a less healthy diet.

In an article on csmonitor.com, Paul Fischbeck, professor of social and decisions sciences and engineering and public policy, said in a statement that consuming lettuce is causing three times more greenhouse gas (GHG) emissions than consuming bacon.

Fischbeck added that many common vegetables require more resources per calorie than one would imagine, and vegetables like eggplant, celery and cucumbers look particularly bad when compared to pork or chicken.

The research looked at the amount of energy consumed to grow, process and transport food to the consumer, as well as energy used in storage at the markets and the home, and took into account water use and GHG emissions also.

The results show that many foods have a much higher GHG emission level per calorie than many of the alternatives.  According to the researchers, eating the diet recommended by the USDA increased energy use about 38 percent, water use by 10 percent and GHG emissions went up six percent as well.

Michelle Tom, a co-author of the study, said what was good for us may not always be the best for the environment, and that it was important for public officials to be aware of this as they develop guidelines for food consumption in the future.  She also acknowledges that the relationship between our diets and the effect on the environment is a complex one.

Senior research fellow Anthony Froggatt at Chatham House, who was unaffiliated with the research team, but is researching the connections between meat production and GHGs, said the results of the study were surprising.  He admitted that vegetables like lettuce can be incredibly water and energy intensive, but the results could be different depending on how the foods are produced and handled.

Froggatt added we usually look at proteins instead of calories, and reducing meat consumption in favor of plant-based proteins can still be counted on to be environmentally friendly.

The findings of the study appeared in the journal Environment Systems and Decisions.