CLIMATE

A sustainable diet leaves room for two chicken breasts a week

We should eat less meat and more legumes, campaigns and dietary advice tell us. But how much is "less"? Researchers from DTU have an answer.

Researchers from DTU have calculated how much of a given ingredient you can eat without harming the planet. Photo: Colourbox

Facts

The nine planetary boundaries are scientifically based estimates of how much human impact the planet itself can compensate for.

For example, when humanity collectively consumes more freshwater than the planet is able to produce, we have breached the planetary boundary for freshwater consumption.

The nine planetary boundaries are:

1. Climate change

2. Loss of biodiversity

3. Freshwater use

4. Land area use

5. Emissions of ozone-depleting chemicals

6. Pollution with man-made substances

7. Release of aerosols into the atmosphere

8. Emissions of nitrogen and phosphorus

9. Loss of calcium carbonate in the ocean

Of the nine planetary boundaries, six have already been breached, according to a 2023 study by the Stockholm Resilience Centre, which first defined the boundaries in 2009. Only numbers five, seven and nine are still at a level that the planet itself is believed to be able to compensate for.

Not either-or

The research team's calculations take into account a number of environmental factors such as COemissions, the consumption of water and land use, as well as the health impact of a particular diet. In total, they have examined more than 100,000 variations of 11 types of diets and calculated their respective environmental and health effects.

And the calculations clearly show that a diet with even moderate amounts of red meat - beef or lamb, for example - exceeds planetary limits.

A pescetarian, vegetarian or vegan diet, on the other hand, is likely to stay within the limits of what the planet can support. But this also depends largely on the specific products included in the diets.

In addition, different combinations of diets, such as vegetarian but with dairy or eggs, can also be sustainable.

And that's exactly what Caroline H. Gebara hopes that the study will help more people realise: That a sustainable diet can take many different forms.

"For example, our calculations show that it's possible to eat cheese if that is important to you, while at the same time having a healthy and climate-friendly diet. The same is true for eggs, fish and white meat, but the premise is of course that the rest of your diet is then relatively healthy and sustainable. But it doesn't have to be either-or."

You can read the full study in Nature Food.

Contact

Caroline Herlev Gebara

Caroline Herlev Gebara Postdoc Department of Environmental and Resource Engineering Mobile: +45 27290616