There’s plenty of research and nutritional studies dedicated to assessing the health benefits of popular diets. But which of these is the healthiest choice for our environment?

Carbon over calories

Researchers have been making the case that what we eat has an impact on the environment, a thesis that has been gaining traction with each new study that confirms it. As recently as 2021, the United Nations delivered a report that outlined how ineffectual food systems were the cause of up to 18 billion tonnes of carbon dioxide, or one third of the world’s total greenhouse gas emissions. It’s clear then that tackling the ongoing climate crisis will involve re-thinking both what and how we eat.

Now a new study aims to put to rest the debate on which foods are best for our planet. Researchers from Tulane University compared six popular diets, scoring them on both overall nutritional quality and carbon emissions. Data was sourced from a survey by the US Centers for Disease Control. The National Health and Nutrition Examination Survey included responses from over 16,000 participants, examining the keto, paleo, pescatarian, omnivore, vegetarian and vegan diets.

Of these, the paleo and keto style diets had the largest carbon footprints, whilst vegan and vegetarian had the lowest. In fact, researchers found that a vegan diet generated only 0.7kg of carbon dioxide per 1,000 calories consumed, which over 75% less than the keto diet. Not only did paleo and keto take the crown for least environmentally sustainable, but they also ranked lowest for nutritional value too.

Even a partial transition to a plant-based diet would have a meaningful impact for the planet.

Lead researcher Diego Rose spoke to the poor environmental rating of the two diets, noting that they “suspected the negative climate impacts because they’re meat-centric, but no one had really compared all these diets.” Diets that were meat-focused also had the poorest nutritional outcomes, a trend that was reversed when participants opted for plant-based diets.

Researchers concluded that even a partial transition to a plant-based diet would have a meaningful impact for the planet and help align with ongoing emission reduction targets.

“If a third of the omnivores consumed a 2000 kcal vegetarian diet… the savings would be equivalent to eliminating 340 million passenger vehicle miles.”

Vegetables in a white bowl, being held in a garden.
Plant-based diets have the lowest impact. Source: Vo Thuy Tien/Pexels.

This latest study confirms the findings of earlier research conducted in 2019 by scientists at the University of Minnesota and Oxford University. This paper similarly analysed the impact of several food groups on both human health and the environment. The team of researchers explored different types of meat, fish, vegetables, nuts, olive oil, sugar-sweetened beverages and whole grain cereals, assessing each against several biological and ecological factors.

“Foods associated with significant reductions in mortality consistently have a low averaged relative environmental impact.”

In the study, consumption of whole grains, fruits and vegetables were associated with lower risk of disease and mortality, while consumption of sugar-sweetened drinks, red meat (both processed and un-processed) were consistently associated with an increased disease risk.

The environmental impact of plant-based food groups was also favourable, with whole grains, fruits, vegetables, nuts and olive oil associated with a lower impact as compared to red meat, which had the greatest environmental impact. Factors included greenhouse gas emissions, land and water use for each food group.

Unsurprisingly then, the researchers concluded that there were clear associations between health and environmental outcomes, finding that “foods associated with significant reductions in mortality consistently have a low averaged relative environmental impact.”

Food for thought

The results of this research are valuable, but only if acted upon. So, how will the average consumer become educated on the environmental impact of what they eat? More and more, we’ve seen companies advertise emissions related to the ongoing operations, in a bid to become more transparent with sustainability efforts. It begs the question, why not include this messaging directly on food products?

Strong Roots is one company doing just that, with the vegan brand featuring a carbon footprint score on the front of its packaging. Others, like Oatly, have followed suit with their own labeling on plant-based versions of its dairy alternatives. It’s a welcome addition to the nutritional information that we’ve become accustomed to seeing over the years, and one that is overdue for meat and dairy products in particular. Hopefully, by putting this information front and centre, consumers will be able to make more sustainable choices that are coincidentally a healthier option too.

Because as indicated by a growing body of research, it turns out that foods that are good for you, tend to be good for the planet too.

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