Paleo and keto diets bad for health and the planet, says study
The health benefits of a meat-based versus a plant-based diet are often hotly debated both in the research community and by self-styled health gurus on social media platforms. A new study adds another checkmark to the plant-based column, this time looping in the environmental impact from choosing the paleo or keto diets over veganism. The findings, the researchers hope, could help people choose diets that are not only nutritious, but environmentally friendly as well.
When it comes to the more extreme ways of eating, the paleo and keto diets are on one side of the field, while veganism is on the other. Paleo dieters focus on meats, vegetables, fruits and nuts while avoiding beans and grains, while Keto practitioners dial back nearly all carbohydrates, focussing instead on meats and fats. Vegans avoid all animal products and animal byproducts in their diet.
While it’s possible to find studies touting some benefits and some drawbacks on human health from both ways of eating, researchers out of Tulane University took a slightly different approach to comparing the eating plans: they tracked how much carbon dioxide paleo and keto diets release into the atmosphere versus a plant-based diet. Carbon dioxide is a key contributor to global warming trends, so understanding how it gets into the atmosphere can help mitigation efforts.
To compile their results, the researchers used information from a database they had previously developed called dataField, which tracks the carbon footprint of various foods. They also examined the nutritional impacts of the various types of diets by applying point values derived from the federal Healthy Eating Index to data from over 16,000 adults participating in the CDC’s National Health and Nutrition Examination Study.
They found that for every 1,000 calories consumed, the keto diet generates nearly 3 kg of carbon dioxide, while the paleo diet releases 2.6 kg of the greenhouse gas into the atmosphere. Vegans, on the other hand, only release 0.7 kg of carbon dioxide for each 1,000 calories they consume, meaning that paleo and keto diets create nearly four times the greenhouse gas emissions as vegan diets. In the middle of the field, omnivores–who made up 86% of those in the study released 2.2 kg of carbon dioxide per 1,000 calories.
The researchers say their findings indicate that if only a third of omnivores switched to a vegetarian diet, the environmental impact would be akin to removing the carbon output of 340 million passenger vehicle miles on any given day.
Healthwise, the study gave the highest marks to pescatarian diets, which release 1.66 kg of carbon dioxide into the atmosphere per 1,000 calories consumed, so it forms a kind of compromise between nutritional quality and carbon emissions. Vegan and vegetarian diets followed close behind in terms of having high nutritional content, while keto and paleo diets lagged.
“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,” said study senior author Diego Rose. “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.”
The study has been published in The American Journal of Clinical Nutrition.
New Atlas, 2 March 2023