Here’s the 571-page report by the Advisory Committee on upcoming Dietary Guidelines:

Scientific Report of the 2015 Dietary Guidelines Advisory Committee, February 2015

Page 7:

“The major findings regarding sustainable diets were that a diet higher in plant-based foods, such as vegetables, fruits, whole grains, legumes, nuts, and seeds, and lower in calories and animal-based foods is more health promoting and is associated with less environmental impact than in the current U.S. diet.”