overhead view of kale on a plate against green background
From vegan to keto, a new study evaluates the health and climate impact of popular diets. Credit – Getty Images—Kilito Chan
Debates over the benefits and pitfalls of different diets have been around as long as, well, the diets themselves. Is the ketogenic diet a good way to lose weight, or a carb-free trip to bad health? Are vegetarians missing out on vital vitamins? What, exactly, is the omnivore’s dilemma? Can vegans eat sugar? And do paleo adherents actually know what our ancient ancestors ate?
A study published this week in The American Journal of Clinical Nutrition can at least put one diet debate to rest: the climate impact of our choices. Our food system is responsible for a third of global emissions—animal agriculture alone makes up 14%—and our diets could have a significant impact on what those emissions look like in the future.
Using data collected from the U.S Centers for Disease Control and Prevention’s (CDC) National Health and Nutrition Examination Survey of nearly 17,000 American adults, researchers at Tulane University identified six popular American diets—vegan, vegetarian, pescatarian, paleo, keto, and omnivore—and compared them on the basis of environmental impact and nutritional quality. The keto diet, which eschews carbs in favor of fats, was the most carbon-intensive, generating approximately 3 kg of carbon dioxide per every 1,000 calories consumed. The paleo diet, which avoids grains, dairy, and legumes, came in second at 2.6 kg of CO2, while the omnivore diet kicked in at 2.2 kg of CO2.
The diets with the lowest carbon footprint—vegan, at 0.7 kg of CO2, and vegetarian at 1.2 kg—were also generally healthier than their carbon intense, meat heavy alternatives, says lead author Diego Rose, the nutrition program director at Tulane University’s School of Public Health and Tropical Medicine, calling it “a win-win for the environment and nutrition.” There was one notable exception: the pescatarian diet, at 1.6 kg of CO2 per 1,000 calories, scored highest in terms of nutrition, based on the USDA’s Healthy Eating Index. (The index is scored out of 100; the closer to…