Comparing the Environmental and Nutritional Impact of Popular Diets

Researchers at Tulane University in New Orleans have conducted an in-depth analysis of six popular diets and their associated environmental and nutritional impacts.^[0] The keto and paleo diets, which prioritize high amounts of fat and low amounts of carbs and eschew grains and beans in favor of meats, nuts, and vegetables, respectively, 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).

Vegan diets had the lowest environmental impact, producing only 0.7kg of CO2 for every 1,000 calories consumed, compared to vegetarian and pescatarian diets. It is interesting to note that pescatarian diets had the best overall nutritional quality and surpassed both vegetarian and vegan diets. Those who consumed a Mediterranean diet, which incorporated a wide variety of vegetables, fruits, whole grains, healthy fats and lean protein, were deemed to have a higher nutritional quality and a smaller carbon footprint than their omnivorous counterparts.^[1] The same was true for the DASH diet, a heart-healthy plan that limits red meat consumption.^[1]

The study’s senior author Diego Rose, professor and nutrition program director at Tulane University School of Public Health and Tropical Medicine, said that while researchers have examined the nutritional impact of keto and paleo diets, this is the first study to measure the carbon footprints of each diet, as consumed by U.S. adults and compare them to other common diets. A 2021 United Nations-backed study found that 34% of greenhouse gas emissions come from the food system, with beef being responsible for 8-10 times more emissions than chicken production and over 20 times more emissions than nut and legume production.^[2]

Rose believes that this research brings to light significant issues regarding how to promote dietary practices that are advantageous for both individuals and the environment.^[2] Policymakers should think about how different policies could bring about better results and promote healthier, more eco-friendly diets.^[3] Noting that those on omnivorous diets who opted for the plant-forward Mediterranean or fatty meat-limiting DASH diet versions, both carbon footprints and nutritional quality scores improved, Rose concluded that “there’s a way to improve your health and footprint without giving up meat entirely.^[4]

0. “The carbon footprints of six popular diets – so how does YOURS stack up?” Daily Mail, 1 Mar. 2023, https://www.dailymail.co.uk/sciencetech/article-11802529/The-carbon-footprints-six-popular-diets-does-stack-up.html

1. “How the keto diet compares to greener eating, in two charts” Insider, 3 Mar. 2023, https://www.insider.com/how-the-keto-diet-compares-to-greener-eating-two-charts-2023-3

2. “Study of popular diets finds over fourfold difference in carbon footprints” Dynamite News, 5 Mar. 2023, https://www.dynamitenews.com/story/study-of-popular-diets-finds-over-fourfold-difference-in-carbon-footprints

3. “Study reveals the environmental impacts of various diets” Earth.com, 1 Mar. 2023, https://www.earth.com/news/study-reveals-the-environmental-impacts-of-various-diets/

4. “Keto, vegan, vegetarian and more: Which diets are best for the environment?” WSB Radio, 2 Mar. 2023, https://www.wsbradio.com/news/local/keto-vegan-vegetarian-more-which-diets-are-best-environment/JZL35FLAOFAFBCWSR4SHHFX7HQ/