'Small swaps' to climate-friendly diet can significantly reduce carbon footprint, improve health: Study

Realistic, simple dietary swaps can help Americans make a difference in the country's carbon footprint, a new study found.

If all consumers swapped their higher-carbon food products for lower-carbon alternatives—things like swapping cow products to plant-based or poultry products—just once a day, models show it could reduce their personal dietary carbon footprint significantly and the total dietary carbon footprint in the U.S by more than 35%, and come with health benefits.

"We know that food production accounts for about 20% of greenhouse gas emissions worldwide," said Anna Grummon, assistant professor of Pediatrics and Health Policy at the Stanford University School of Medicine and lead author on the study. "We found that making small changes in what we eat can substantially reduce carbon pollution and also make our diets healthier."

The authors of the study, which was published Thursday in Nature Food, simulated the environmental and health impacts of simple dietary substitutions in more than 7,700 Americans. They identified commonly eaten foods with the highest carbon footprints in the diets of those people and modeled what would happen if they replaced them with nutritionally similar, lower-emission options.

They found that small swaps here and there could add up to a big difference.

The study found that food swaps toward diets high in fruits, vegetables, and legumes and lower in red and processed meats can reduce a person's carbon footprint from food production.

Specifically, swapping out beef for lower carbon footprint protein options like poultry or plant-based alternatives could lead to a more than 50% reduction in a person's daily carbon footprint, and swapping out cow's milk for plant-based milks could lead to an almost 8% reduction in a person's daily carbon footprint.

"We modeled replacing one food with another similar food, so replacing a beef cheeseburger with a turkey cheeseburger, or a beef burrito with a chicken or bean burrito, so really trying to keep the swap similar," Grummon said. "Making those, we call them "small changes" or "small swaps," can substantially reduce the carbon pollution from our food production."

The carbon footprint for each food looked at its full life cycle, including the emissions from production, transport, and eventual disposal, said Diego Rose, nutrition program director at Tulane University School of Public Health and Tropical Medicine and senior author on the study. He says this allowed them to look not just at specific foods, but at mixed dishes like a pizza or lasagna.

This idea that more sustainable eating choices can help curb climate change is not new. But this study shows the potential big impact of just small daily choices.

"Of course, the ideal is to make this change all the time, but that's really hard," said Grummon. "Even making a change just once a day or once a week, that can still be beneficial."

The bonus here was the finding that these same swaps could also benefit health.

The researchers used the Healthy Eating Index, based on the USDA Dietary Guidelines, to identify which foods were things people should eat more of—like fruits, vegetables, and whole grains—or less of—like high salt, high saturated fat foods.

"We scored everybody's diet before the simulated change and after," Rose said. After the swaps from higher to lower-carbon foods, overall dietary quality improved by four to ten percent.

"It's a win-win," Rose said. "You can reduce environmental impact and improve your diet quality at the same time."

The relationship between diet, health, and climate change is complex, but many experts agree that meat consumption, beef in particular, represents the majority of the carbon footprint in the American diet with 56% of the carbon footprint in all diets in the US coming from beef. And the U.S dietary guidelines already recommend that if you are getting protein from meat, you should choose lean meats like chicken breast over processed meats.

Representatives from the dairy and beef industry said that their products should still be a part of Americans' diets.

Lori Captain, executive vice president of Sustainability for Dairy Management Inc., an organization funded by U.S. dairy farmers and importers, says that the dairy industry has seen "really significant contributions by U.S. dairy farmers to making environmental improvements," and continues to do so.

The National Cattlemen's Beef Association says that beef and other foods like poultry or plant-based options are not interchangeable. They say that "at a time when hunger and malnutrition are widespread in the United States and globally, there's a growing urgency to encourage nutrient-dense foods like beef…which help contribute to improved nutrition security, health, and well-being."

But that's the benefit of a "small changes" approach, the authors say.

"We're not modeling complete replacement of all red meat, Grummon said. "According to their findings, people of all ages and demographics can make "small swaps" in their daily diet and still see benefits both for their health and for the planet.

"We looked at these changes across different population groups and we'd see that, no matter your race or your age or your gender, these substitutions are beneficial, so it's sort of a story that anyone can do this and anyone can make a difference with it," Grummon said.

Both Grummon and Rose say this study left them hopeful.

"For folks who are interested in reducing their personal carbon footprint, start where you can. If that is changing just one thing a week, start there and then see if that can grow, but don't be intimidated by the size of the problem," said Grummon. "These small changes can add up to be meaningful, even if you're only doing it once a day or once a week."

Dr. Elizabeth Ghandakly, MD JD, is a resident physician in Internal Medicine from The Cleveland Clinic in Ohio and a member of the ABC News Medical Unit.