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20% of U.S. Diets Responsible for Almost Half of Country’s Food-Related Emissions, Study Finds

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If you've been deliberating about going vegetarian, a study published Tuesday in Environmental Letters might give you the final push.


The study was the first to look at the environmental impact of individual diets in the U.S., and found that 20 percent of Americans account for 46 percent of the country's food-related greenhouse-gas emissions. Seventy percent of the emissions that resulted from the diets of that 20 percent came from meat consumption, according to a press release about the study published by the University of Michigan on EurekAlert!.

The consumption of beef accounted for 72 percent of the difference between the highest and lowest 20 percent of emitters, the release also reported. Overall, the top 20 percent of diets caused 7.9 times the greenhouse gas emissions as the bottom.

"A big take home message for me is the fact that high-impact diets are such a large part of the overall contribution to food-related greenhouse gases," the study's lead author and University of Michigan researcher Martin Heller said in the release.

To obtain these results, researchers at the Center for Sustainable Systems at the University of Michigan's School for Environment and Sustainability and Tulane University's Department of Global Community Health and Behavioral Sciences calculated the impact of individual diets by determining the greenhouse gas emissions and non-renewable cumulative energy demand of 332 food commodities in the Food Commodities Intake Database developed by the Environmental Protection Agency. These were linked to the recollections of more than 16,000 Americans of their previous day's diet collected by the U.S. National Health and Nutrition Examination Survey from 2005 to 2010. The study focused only on food-production-related emissions and did not include packaging, cooking, freezing, distribution or processing, factors Heller said in the release could raise total emissions by at least 30 percent.

While the study confirmed previous research finding that meat and dairy contribute the most to U.S. diet-related emissions overall, it also found that beverages, including water, coffee, tea, soft drinks and alcohol, played a larger role than expected, accounting for almost 6 percent of emissions and 16 percent of non-renewable cumulative energy demand.

According to the release, the top 20 percent of dietary emitters also consumed two times as many calories as the bottom 20 percent. However, when the data was adjusted for caloric intake, the top quintile was still responsible for five times the emissions of the bottom.

For Heller, the results indicated that individual dietary choices can make a difference in reducing national emissions.

If that top 20 percent, representative of 44.6 million Americans, reduced the greenhouse gas emissions of their diet to the national average every day, and production followed suit, that would account for 9.6 percent of the emissions reductions needed for the U.S. to meet its 2025 commitments under the Paris agreement, the study found. According to the release, food production was responsible for about 8 percent of U.S. emissions in 2010.

"Reducing the impact of our diets—by eating fewer calories and less animal-based foods—could achieve significant reductions in greenhouse gas emissions in the United States. It's climate action that is accessible to everyone, because we all decide on a daily basis what we eat," Heller said in the release.

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