Climate-friendly diets also healthier: study

The researchers ranked diets by the amount of greenhouse gas emissions per 1,000 calories consumed and divided them into five equal groups. (Unsplash Photo)

CHICAGO — After examining the carbon footprint of what more than 16,000 Americans eat in a day, a study conducted by researchers at the University of Michigan (UM) and Tulane University shows that more climate-friendly diets are also healthier.

The 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 US 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 are not healthy, namely added sugars and refined grains. They also had lower amounts of important nutrients, such as iron, calcium, and vitamin D.

Overall, diets in the lowest-impact group were healthier, but not on all measures.

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, 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 US 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,” said study co-author Martin Heller of the UM Center for Sustainable Systems at the School for Environment and Sustainability. “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.”

“We hope these findings will help the public and policymakers recognize that improving diet quality can also help the environment,” Heller added.

The study was published online Thursday in the American Journal of Clinical Nutrition.