Lower-carbon diets aren’t just good
for the planet, they’re also healthier
A new study examining the carbon
footprint of what more than 16,000 Americans eat in a day has good news for
environmentally conscious consumers: diets that are more climate-friendly are
also healthier.
The study, conducted by researchers
at the University of Michigan and Tulane University, is the first to compare
the climate impact and nutritional value of U.S. diets using real-world data
about what Americans say they are eating.
The paper is an online
publication in the American Journal of Clinical Nutrition on Jan. 24.
“We hope these findings will help the public and policymakers recognize that improving diet quality can also help the environment,” said study co-author Martin Heller of the U-M Center for Sustainable Systems at the School for Environment and Sustainability.
“People whose diets had a lower
carbon footprint were eating less red meat and dairy—which contribute to a
larger share of greenhouse gas emissions and are high in saturated fat—and
consuming more healthful foods like poultry, whole grains and plant-based proteins,”
said lead author Diego Rose, a professor of nutrition and food security at
Tulane University’s School of Public Health and Tropical Medicine.
Because food production is a major
contributor to climate change, the researchers sought to learn more about the
impacts of Americans’ daily dietary choices. They built an extensive database
of the greenhouse gas emissions related to the production of foods and linked
it to a large federal survey that asked people what they ate over a 24-hour
period.
Researchers ranked diets by the
amount of greenhouse gas emissions per 1,000 calories consumed and divided them
into five equal groups. Then they rated the nutritional value of foods consumed
in each diet using the U.S. Healthy Eating Index, a federal measure of diet
quality, and compared the lowest to the highest-impact groups on this and other
measures.
Americans in the lowest-carbon
footprint group ate a healthier diet, as measured by this index.
However, these diets also contained more of some low-emission items that aren’t healthy, namely added sugars and refined grains. They also had lower amounts of important nutrients—such as iron, calcium and vitamin D—likely because of the lower intakes of meat and dairy.
However, these diets also contained more of some low-emission items that aren’t healthy, namely added sugars and refined grains. They also had lower amounts of important nutrients—such as iron, calcium and vitamin D—likely because of the lower intakes of meat and dairy.
Overall, diets in the lowest-impact
group were healthier, but not on all measures. Rose says this is because diets
are complex with many ingredients that each influence nutritional quality and
environmental impacts.
“This explains the nuanced
relationship we observed between these outcomes,” he said.
Diets in the highest-impact group
accounted for five times the emissions of those in the lowest-impact group. The
highest-impact diets had greater quantities of meat (beef, veal, pork and
game), dairy and solid fats per 1,000 calories than the low-impact diets.
Overall, the high-impact diets were
more concentrated in total proteins and animal protein foods. A companion study
the researchers released last year found that 20 percent of Americans accounted
for almost half of U.S. diet-related greenhouse gas emissions.
“The good news here is that there
are win-win solutions with diets that are healthier for people and planet,”
Heller said. “Big reductions in food-related emissions don’t require
eliminating foods entirely: moderate shifts away from red meat and toward
beans, eggs or chicken can lead to significant improvements in both health and
our diet’s carbon footprint.”