Sustainable diets have been a topic of fervent interest like never before. Now, a recent study published in the Environment Systems and Decisions journal is adding fuel to the ﬁre, prompting sensationalist headlines like “Lettuce Produces More Greenhouse Gas than Bacon Does” or “Vegetarian Diets Hurt the Planet, Too.” Perhaps not surprisingly, a closer investigation of the evidence shows that these headlines aim to provoke, not to inform, as traditional diets featuring an abundant variety of plant foods are the clear environmental winners.
First and foremost, the study in question did not even look at vegetarian or vegan diets. Rather, it measured the diﬀerence in environmental impact if we shift our current American diet to one of three eating patterns: our current American diet but with fewer calories, a USDA recommended eating pattern (based on the Dietary Guidelines) at our current calorie level, or a USDA recommended eating pattern with fewer calories. The study found that switching to a USDA recommended diet at either calorie level would lead to increased greenhouse gas emissions, water use, and energy use, making some journalists question exactly what an earth-friendly diet might look like.
Considerations about the sustainability of food have never made it into the dietary guidelines, so it’s no surprise that the USDA recommended diet isn’t the poster child for sustainability. This shift would require much more dairy consumption, as well as more seafood, fruits, and vegetables. Lots of dairy and intensively raised ﬁsh isn’t going to be easy on the earth, which is precisely why it’s important to consider environmental impact when creating dietary guidelines.
That said, the misguided uproar about the large environmental impacts of fruits and vegetables is completely unfounded. In a chart from the study itself, the researchers show that the greenhouse gas emissions per calorie of meat, poultry, and eggs are actually higher than that of fruits and vegetables. This is consistent with everything we know about agriculture and the environment. After all, livestock also drains environmental resources in other ways not addressed in the study. Three fourths of our land is used to produce animal products, which provide only 17% of our calories, using a vast amount of resources to feed only a small proportion of people.
Additionally, when portraying lettuce as a resource hog, researchers compared environmental impact per calorie. The authors wrongly assumed that if people ate less bacon, they would make up the same amount of calories in vegetables. However, skipping just four slices of bacon would mean that you’d have to replace it with two large heads of lettuce – an amount unfathomable to even the most prudent plant-based enthusiasts.
Even for those that are drawn to large salads and colorful, plant-based meals, fruits and vegetables aren’t the main source of calories, since they have very few calories to begin with. Rather, those embracing traditional, plant-based diets get their calories from grains, beans, nuts, and seeds. Not only do these nourishing plant foods provide more energy, they are also easier on the planet. Indeed, research shows that grains require only 0.51 liters of water per calories, compared to 2.09 liters per calorie of fruits, 1.34 liters per calorie of vegetables, and 10.19 liters for beef. Additionally, when declaring the high environmental impact of fruits and vegetables, authors used our current produce preferences (lettuce, celery, tomatoes, etc.) instead of considering the full spectrum of healthy, low impact vegetables (like cabbage, beans, or lentils).
Traditional diets based on beans, whole grains, seeds, and seasonal produce nurture both healthy people and a healthy planet, and real world data backs this up. According to the United Nations Food and Agriculture Organization, vegetarian diets around the world use less water than meat containing diets. Similarly, a study of over 70,000 people in California found that the diets of vegetarians produce 22-29% less greenhouse gases than that of meat eaters.
Research and common sense tell us that skimping on salads in favor of beef and bacon isn’t the path to optimal planetary (or human) health. For a scrumptious, sound approach to environmental health, take a cue from the old ways of eating, and try our ten tips for embracing a sustainable diet.
Kelly Toups, Whole Grains Council Program Manager