dietary guidelines and greenhouse gases
September 8, 2014

Following USDA Dietary Guidelines Could Increase Greenhouse Gas Emissions

Chuck Bednar for redOrbit.com - Your Universe Online

If Americans followed dietary guidelines passed by the USDA in 2010 while maintaining their current caloric intake, it would increase food-related greenhouse gas emissions by 12 percent, researchers claim in a new study appearing in the September 5 edition of the Journal of Industrial Ecology.

On the other hand, if they reduced the amount of calories they consumed each day to the recommended level of approximately 2,000 calories while adopting a healthier diet, greenhouse gas emissions would decrease by one percent, study authors Martin Heller and Gregory Keoleian of the Center for Sustainable Systems at the University of Michigan’s School of Natural Resources and Environment explained in the new study.

“The take-home message is that health and environmental agendas are not aligned in the current dietary recommendations,” Heller said in a statement Friday. He added that the findings are of particular relevance since the USDA’s Dietary Guidelines Advisory Committee is currently considering food sustainability as a factor when determining the next set of dietary recommendations.

In its 2010 dietary guidelines, the agency recommended that Americans consume more fruits, vegetables, whole grains, fat-free and low-fat dairy products, seafood, less salt, saturated fat, trans fat, cholesterol, added sugar and refined grains, the researchers explained. While the guidelines do not explicitly state that people should eat less meat, an appendix to the report does recommend eating significantly less meat than is currently consumed.

Those recommendations echo those of a team of UK researchers, who published research in the journal Nature Climate Change last Sunday which warned that, unless global red meat and dairy product consumption was reduced, greenhouse gases resulting from food production could increase by as much as 80 percent by the year 2050.

“The average efficiency of livestock converting plant feed to meat is less than 3 percent, and as we eat more meat, more arable cultivation is turned over to producing feedstock for animals that provide meat for humans,” lead investigator Bojana Bajzelj, a research associate in the University of Cambridge’s Department of Engineering, told BBC News at the time.

“The losses at each stage are large, and as humans globally eat more and more meat, conversion from plants to food becomes less and less efficient, driving agricultural expansion and releasing more greenhouse gases,” she added. “Agricultural practices are not necessarily at fault here – but our choice of food is.”

The authors of the new study also report that a drop in meat consumption would help cut diet-related greenhouse gas emissions, and that consuming more dairy products would increase those emissions. In 2010, food production was responsible for roughly eight percent of the country’s greenhouse gas emissions, and generally speaking, animal-based foods are responsible for more greenhouse gas emissions per pound than plant-based foods.

“The production of both beef cattle and dairy cows is tied to especially high levels of greenhouse gas emissions,” the university explained. Cows are inefficient at converting plant-based food into milk or muscle, meaning that more food needs to be grown in order for them to eat their fill. Growing that feed typically requires the use of fertilizers and other substances that require much energy to process, as well as farm equipment that requires fuel.

In addition, the researchers note that the gaseous emissions and manure of cows release a lot of methane. Because of those combined factors, the greenhouse gas emissions associated with diets are dominated by meat products, with Heller and Keoleian noting that beef accounts for just four percent by weight of the available food while contributing 36 percent of the affiliated greenhouse gas emissions.

The Michigan researchers report that switching to diets which do not contain animal products would result in the largest total reduction in food-related greenhouse gas emissions, but Heller emphasizes that he is not advocating a nationwide switch to vegan diets. He said that he feels animals have to be part of a sustainable agricultural system, but added that reducing consumption of these goods would benefit both personal and ecological health.

Professor Keith Richards, who was a co-author of the Nature Climate Change study, shared similar thoughts in August: “This is not a radical vegetarian argument; it is an argument about eating meat in sensible amounts as part of healthy, balanced diets. Managing the demand better, for example by focusing on health education, would bring double benefits – maintaining healthy populations, and greatly reducing critical pressures on the environment.”

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