A new study has confirmed a vegetarian diet does the least harm to the planet.
The research, published in the journal The Lancet Planetary Health, measured the impacts on global warming, land use and water for three diets recommended in federal guidelines.
It compared the impacts of vegetarian, mediterranean, and U.S. style diets that include lean meats.
The dietary guidelines, set by the U.S. Departments of Health and Human Services and the U.S Department of Agriculture, influence more than $80 billion in federal spending on food-related programs such as the National School Lunch and Breakfast Programs, nutrition programs for women, infants and children and meal programs for the elderly.
Hampshire College's new president, Miriam Nelson -- a nutrition policy researcher -- co-authored the study.
"If we could slowly decrease the amount of animal foods, especially beef, pork and chicken," said Nelson, "and increase the amount of plant-base foods, people would actually be healthier, but we will also have more sustainable diets over time."
Although the U.S. government chose not to include sustainability in its dietary guidelines in 2015, other countries have, including the Netherlands, Sweden and Brazil.