Climate change mitigation and health effects of varied dietary patterns in real-life settings throughout North America.

BACKGROUND Greenhouse gas emissions (GHGEs) are a major consequence of our dietary choices. Assessments of plant-based compared with meat-based diets are emerging at the intersection of public health, environment, and nutrition. OBJECTIVES The objective was to compare the GHGEs associated with dietary patterns consumed in a large population across North America and to independently assess mortality according to dietary patterns in the same population. DESIGN Data from the Adventist Health Study 2 (AHS-2) were used to characterize the differential environmental and health impacts of the following 3 dietary patterns, which varied in the quantity of animal and plant foods: vegetarian, semivegetarian, and nonvegetarian. The GHGE intensities of 210 foods were calculated through life-cycle assessments and by using published data. The all-cause mortality rates and all-cause mortality HRs for the AHS-2 subjects were adjusted for a range of lifestyle and sociodemographic factors and estimated according to dietary pattern. RESULTS With the use of the nonvegetarian diet as a reference, the mean reductions in GHGEs for semivegetarian and vegetarian diets were 22% and 29%, respectively. The mortality rates for nonvegetarians, semivegetarians, and vegetarians were 6.66, 5.53, and 5.56 deaths per 1000 person-years, respectively. The differences were significant. Compared with nonvegetarians, mortality HRs were lower for semivegetarians (0.86) and vegetarians (0.91). CONCLUSIONS Moderate differences in the caloric intake of meat products provided nontrivial reductions in GHGEs and improved health outcomes, as shown through the mortality analyses. However, this does not mean that diets lower in GHGEs are healthy.