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Eat Your Veggies for a Lower Carbon Footprint, New Study Says

A table filled with healthy foods.
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Scientists at the University of California Los Angeles (UCLA) found that diets involving the consumption of plants and unprocessed foods are not only good for your body, they’re also better for the planet than the standard American diet. The research is published in Nutrients.

What you eat affects the health of the planet

Deciding what to eat isn’t always the most straightforward process. There are many individual factors that contribute to our food choices, like specific dietary requirements, for example. Perhaps you rustle up a certain recipe because it brings you pleasure, or because it’s convenient. Maybe you eat based on your knowledge of how food can support your overall health and wellbeing.

While our food choices may be unique, their impact extends beyond us as individuals – it affects the health of the entire planet. Twenty six percent of global greenhouse gas emissions are associated with food production and consumption.

UCLA researchers sought to explore the link between human health and the environment by comparing carbon-footprint values and health benefits of six popular diets:

  • The standard American diet
  • Mediterranean diet
  • Vegan diet
  • Paleo diet
  • Keto diet
  • Climatarian diet

The latter involves reducing the consumption of foods known to have large carbon footprints, such as red meat or out-of-season produce. The team was led by Kiera Dixon, a scientist working in environmental health at the UCLA Fielding School of Public Health.

What is a carbon footprint?

Generally, an item’s carbon footprint is described as the amount of greenhouse gas – particularly carbon dioxide – that is emitted in association with that item during a given period. A food item’s carbon footprint accounts for the gases emitted during its manufacturing, processing, transport and disposal, for example. 

“The purpose of our study was to evaluate food choices that represent consumption patterns found in popular diets and their potential impacts on climate change. We also evaluated the impacts of these diets on human health to provide an understanding about whether diets that are healthy and promote disease prevention also contribute toward a reduction of the environmental burden required for food production,” the authors write. “While all diets require resources from the environment for food production and transportation, some may be more impactful than others.”

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Standard American diet has greatest carbon footprint

Dixon and colleagues leveraged carbon emission information from databases featured in peer-reviewed journal articles, including the SU-EATABLE LIFE database (SEL), published in 2017. The SEL database was supplemented with data from the work of Song et al – Large-Scale Microanalysis of U.S. Household Food Carbon Footprints and Reduction Potentials – published in 2021.

The team quantified the carbon emissions associated with each of the popular diets, and reviewed the typical foods consumed in an average day. They limited their analysis to foods available in North America and standardized the data to 2,000 calories consumed each day.

Their findings, summarized in Table 1, suggest that the standard American diet – which is consumed by over 80% of the US population – takes the trophy as the most carbon-intensive, followed by the keto and paleo diets. These three diets were categorized as higher-emission diets by Dixon and team, while the Mediterranean, vegan and climatarian are lower-emission diets. “The primary determining factor for this observation was the regular consumption of red meat in the higher-footprint variations of the high-emission diets. When higher-impact meat, such as beef, is replaced with lower-impact meat, such as chicken or pork, there is a significant decrease in the carbon footprint of the standard American, keto and paleo diets,” the researchers describe.


Table 1: This table summarizes the overall findings of Dixon, Michelsen and Carpenter’s study. The table lists each type of diet, a description of the typical foods consumed, its carbon emissions per day per person and how these emissions compare to those produced by driving a car.  



Carbon emissions per day per person

Equivalent carbon emissions in distance driven by car

Standard American

Five main food groups; no reduction of salt, sugar, saturated fats or processed food.

5.8 to 18 pounds

6.5 to 20 miles


Focused on whole grains, fruit and vegetables, fish and olive oil; includes animal products but excludes processed food.




Excludes animal-based products.




Excludes processed food and sugars, salts, grains and most dairy.

6.9 to 13

7.7 to 14.6


Focused on protein and fat-rich products; limits sugar and grains.

10.7 to 21.4

12.0 to 24.0


Focused on local, seasonal and fresh food; limits non-sustainable animal products and processed food.

4.1 to 5.6

4.7 to 6.3


Good for your body, good for the planet

The researchers say that their findings support the notion that diets carrying more health benefits for the human body are also healthier for the planet. Diets heavy in red meat are typically classified as the most “unhealthy” due to their association with increased disease risk. “Our results demonstrate that the consumption of red meat is the largest contributing factor toward a high-carbon-footprint diet, as is evidenced by the drop in carbon-footprint values when meat-substitution calculations were carried out,” the authors note.

Taken from Technology Networks. 

“You can decrease your individual carbon footprint quite significantly and still consume meat, but it is highly dependent on the type of meat that you're consuming,” says Malia Michelson, a third-year undergraduate student at UCLA and co-author of the paper.

Dixon and colleagues note that climate-friendly food is typically more expensive, and the ability of populations to reduce the climate footprint of their diet may be affected by financial considerations. To that end, they encourage the government to support people in buying healthier foods by subsidizing their costs. They also suggest that corporations and large organizations could work to make healthier food more accessible, while producers could improve their labeling approaches to improve information for the public about a food’s impact on the climate.

The study carries limitations which must be accounted for, such as the fact that only one component of a food item’s environmental impact was evaluated – its carbon footprint. Additional factors, such as water footprint, could not be included in the analysis due to limited data, the researchers say.

“A future of food consumption that benefits both humans and the environment should be flexible and involve an emphasis on whole, plant-based foods combined with a reduced consumption of meat and processed food. These behavioral changes can be supported by increasing the availability and accessibility of detailed food-life-cycle assessments,” the researchers conclude.

The study was conducted in collaboration with a snack food company, which was seeking to compare the carbon footprints of various diets. The researchers state that the company was not involved in the research or the writing of the publication.

This article is a rework of a press release issued by the University of California Los Angeles. Material has been edited for length and content.

Reference: Dixon KA, Michelsen MK, Carpenter CL. Modern diets and the health of our planet: An investigation into the environmental impacts of food choices. Nutrients. 2023; 15(3):692. doi:10.3390/nu15030692

Meet the Author
Molly Campbell
Molly Campbell
Senior Science Writer