"It's superb that we have this information," Behrens said. "You can trace the impact of any consumption across the world."
For this study, Behrens gathered data on the average diets of people living in 39 countries as well as the dietary recommendations put out by governments in those countries. To make sure the results represented the recommended ways of eating and not just eating less, he kept the calorie counts of both diets the same, and only altered the percentage of the different food groups that people actually eat, and how much their governments suggest they eat.
Next, he fed those data points into Exiobase and compared the outcome.
Specifically, he looked at three ways the environment is affected by our diets -- greenhouse gas emissions, land use and eutrofication, which is the addition of nutrients to water sources that can lead to toxic algae blooms and lack of oxygen in the water. Eutrofication is usually caused by the discharge of animal waste (dung) and plant fertilizer.
The results were far from uniform, but in broad strokes, he found that the wealthiest countries would lower their environmental impact if their citizens followed nationally recommended diets, primarily because most of these recommendations call for a significant reduction in the amount of meat citizens consume.
"In general, meat is worse than other types of food because every time something eats something else, you get a loss of energy," Behrens said. "Eating any animal is going to have more of an impact compared to other food groups."
Poorer countries such as India and Indonesia would see their environmental impact go up, mostly because the nationally recommended diets call for more calories than many citizens consume in those countries.
Still, the overall effect, if everyone followed nationally recommended diets, would be a decrease in greenhouse gases, eutrofication and land use, he said.
A few countries, including Britain, Switzerland and China, have acknowledged that their dietary recommendations will also help create a healthier Earth, but that message is rarely conveyed to citizens, Behrens said.
He thinks it's a lost opportunity.
"Dietary recommendations can be a great way to talk about human health and the health of the environment," he said. "The main point is you can win both ways."
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