Study reveals the environmental impacts of various diets

According to recent studies, about 34 percent of greenhouse gas emissions come from the food system, particularly from food production, with beef production being responsible for eight to ten times more emissions than chicken production, and over 20 times more emissions than nut and legume production. Now, a team of researchers led by Tulane University has used data from more than 16,000 adult diets collected by the CDC’s National Health and Nutrition Examination Survey to examine popular contemporary diets – such as the keto, paleo, vegan, or omnivorous diets – in terms of their nutritional quality and environmental impact. 

The analysis revealed that the keto diet, which prioritizes high amounts of fats and low amounts of carbs, and the paleo diet, which eschews beans and grains in favor of meats, nuts, and vegetables, scored among the lowest on overall nutrition quality and were among the highest on carbon emissions (with 3kg and 2.6kg of CO2 for every 1,000 calories consumed, respectively).

“We suspected the negative climate impacts because they’re meat-centric, but no one had really compared all these diets – as they are chosen by individuals, instead of prescribed by experts – to each other using a common framework,” said study senior author Diego Rose, a professor of Nutritional Sciences at Tulane.

By contrast, vegan diets were found to have the least environmental impact, generating only 0.7kg of CO2 per 1,000 calories consumed, followed by vegetarian and pescatarian diets. The latter scored the highest on nutritional quality, with vegetarian and vegan diets following closely behind. 

The omnivore diet – the most common diet, represented by 86 percent of the survey participants – was in the middle in terms of both quality and sustainability. According to the experts, if a third of people on omnivorous diets started eating a vegetarian diet, on average for any given day, it would be equivalent to eliminating 340 million passenger vehicle miles.

“Climate change is arguably one of the most pressing problems of our time, and a lot of people are interested in moving to a plant-based diet. Based on our results, that would reduce your footprint and be generally healthy. Our research also shows there’s a way to improve your health and footprint without giving up meat entirely,” Rose explained.

“I think the next question is how would different policies affect outcomes and how could those move us toward healthier, more environmentally friendly diets,” he concluded. 

The study is published in the American Journal of Clinical Nutrition. 

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By Andrei Ionescu, Earth.com Staff Writer

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