Mediterranean, Vegetarian, or Vegan—Which Diet is Best for the Planet?

The effect of five widespread diets, including the Mediterranean, vegetarian, and vegan on our planet was examined by a team of Australian scientists. The team argues that the vegetarian diet may be better for the planet, but the Mediterranean diet is the one omnivores would actually adopt.

By Nicole Allenden, Amy Lykins and Annette Cowie

What we eat and how we produce food matters. Food systems are responsible for more than a quarter of the world’s greenhouse gas emissions.

We cannot fully tackle the climate crisis without reducing the greenhouse footprint of our food. The issue is only becoming more urgent, as world population climbs alongside hunger stemming from war disruption of food exports. As people get richer and become urbanized, global consumption of meat and dairy products also grows.

Livestock are the main source of our food emissions and the third highest global source of emissions at 14.5 percent, after energy (35 percent) and transport (23 percent).

To cut these emissions, many advocate switching to plant-rich or plant-only diets. But will people who have a longstanding attachment to meat actually choose to switch over? Our new research suggests the sweet spot is the Mediterranean diet, which includes some meat while remaining plant-rich and healthy.

How our diet affects the planet

Rearing livestock requires massive areas of land as well as inputs of water and feed. More intensive livestock production is linked to biodiversity loss, land degradation, pollution of waterways, increased risk of zoonotic diseases such as COVID-19, and antibiotic resistance.

While methods of cutting livestock emissions are undergoing development, production is only half the story. To have a real impact, we also need to consider demand.

Without reducing the overall demand for meat and dairy, it’s unlikely livestock emissions will fall fast enough and significantly enough. In wealthy countries, such as Australia, we consume meat and dairy at high rates. Reducing these consumption rates could cut greenhouse emissions and reduce other environmental damage.

So which diet should we adopt? Clearly, any acceptable diet needs to be nutritionally adequate. While meat provides essential nutrients, too much of it is linked to diseases such as cancer. It’s important to consider both the environmental and health credentials of a diet. We can add animal welfare to this, as well, which tends to be worse in intensive livestock production.

We hope by identifying healthy, environmentally-sustainable diets with better animal welfare that we can help people make sustainable dietary choices.

Comparison of five diets to save the planet

We looked at five common plant-rich diets and assessed their impacts on the environment (carbon footprint, land, and water use), human health, and animal welfare. We focused on food production in high-income countries.

Among the diets we examined was the Mediterranean diet, which is plant-heavy with small amounts of red meat and moderate amounts of poultry and fish. The  Flexitarian, or semi-vegetarian diet is aimed at meat reduction while, of course, the Vegetarian diet relies on the complete exclusion of meat but allows dairy and eggs. Another diet that was examined was the Pescatarian diet, which only allows fish but no meat. Finally, the fifth diet that was analyzed was the Vegan diet which completely excludes any and all animal products.

All five of these plant-rich diets had less environmental impact than the omnivore diet, with no-meat diets (vegan and vegetarian) having the least impact.

The caveat, however, is that environmental footprint measures used to compare diets are simplistic and overlook important indirect effects of shifting diets.

Overall, the Mediterranean diet was deemed the healthiest for humans while the vegan and vegetarian diets had the best outcomes for animal welfare. When we combined all three measures, vegan and vegetarian diets were found to be the most ‘sustainable’ diets based on reducing our food footprint, staying healthy, and reducing negative impacts on farm animals.

Vegetarian diets are best, but Mediterranean is more popular

There is often a gulf between what we should do in an ideal world and what we actually do. To tackle this, we examined what people are actually willing to eat. Is promoting a vegan or vegetarian diet the most effective way to reduce demand for meat and dairy?

To find out, we asked 253 Australians what they currently eat and which of the five plant-rich diets they would be willing to adopt.

Australia is a high meat-eating country, so it’s not surprising that most of our respondents (71 percent) identified as omnivores.

It’s also no surprise that the diets least likely to be adopted were the vegan and vegetarian diets, as these diets represented a major shift in most people’s eating habits.

As a result, it was the Mediterranean diet, which entails a small reduction in meat consumption, that had the highest likelihood of adoption. Combined with its high health benefits and moderate environmental and animal welfare impacts, we identified it as the best diet to promote.

While some of these results may seem intuitive, we believe by combining social, environmental, human health, and animal welfare elements of food consumption that we gain a more complete picture to spot pitfalls as well as realistic solutions.

For instance, it’s likely a waste of precious time and resources to promote diets like the vegan diet which, realistically, most people are not willing to adopt. Yet, despite the evident lack of enthusiasm from people, most research assessing the environmental impact of different diets has favored vegan and vegetarian diets.

That’s why taking a wider view is important. If we actually want to reduce meat and dairy consumption, we must use approaches that are most likely to work.

In high-income countries, such as Australia, that means we should promote the Mediterranean diet as the best diet to begin to tackle the demand for emissions-intensive meat and dairy. We need to start at a realistic point to begin to create a more sustainable, global food system.

Nicole Allenden is a PhD Candidate, School of Psychology, University of New England; Amy Lykins is an Associate Professor in Clinical Psychology, University of New England; and Annette Cowie is a Principal Research Scientist on Climate.

The article was published in The Conversation with the title “Vegetarian diets may be better for the planet – but the Mediterranean diet is the one omnivores will actually adopt” and is republished under a Creative Commons License.