Can we really eat a healthy balanced diet and help to look after the planet at the same time? This study shows that by changing the types and amounts of foods we eat, it is possible to eat in a way that meets our nutritional needs while also reducing pressures on the environment.
We are becoming much more aware that farming practices and the processing and transport of our food can have a massive impact on the environment. One indicator of this impact is greenhouse gas emissions (GHGE) – such as carbon dioxide, methane, nitrous oxide – which cause heat from the Earth’s surface to be retained in the lower atmosphere and are largely responsible for global warming.
We now know that animal source foods especially red meat are among the largest contributors to GHGE, whereas vegetables, fruits and legumes/pulses/nuts are associated with the lowest GHGE.
Achieving a sustainable diet in Europe
A sustainable diet has a low impact on the environment, provides enough nutrients, is affordable and is culturally acceptable to the people who eat it. This study has looked at the dietary changes that would be needed to achieve a nutritionally adequate diet with lower GHGE in five European countries.
“The Food and Agriculture Organization (FAO) defines sustainable diets as “protective and respectful of biodiversity and ecosystems, culturally acceptable, accessible, economically fair and affordable, nutritionally adequate, safe and healthy, while optimizing natural and human resources”.’ – Vieux et al, 2018.
Food swaps were needed for a nutritionally adequate diet
The authors found about people’s usual diets by asking groups of 18–64-year-olds in five countries (France, UK, Italy, Finland, Sweden) to complete a food survey. Then they estimated the nutrient content and GHGE for 151 food items, grouped into 10 main food groups.
Using a computer programme, the authors designed diets for men and women in each country that met nutritional needs while reducing GHGE, remaining as close as possible to the average diet of the national population.
They found that in most countries, men and women were failing to eat the best diet when it came to nutrient content. To achieve a diet with adequate nutrients, it was necessary to swap some foods in the average diet for foods from different food groups. However, these swaps were associated with an increase in GHGE.
‘Setting nutritional goals with no consideration for the environment may increase GHGE.’ – Vieux et al, 2018.
How much can we reduce GHGE by changing our diet?
Next the authors looked at the food swaps within food groups that would be needed to maintain nutrient content and at the same time reduce GHGE.
The maximum reduction in GHGE that was theoretically possible was 62–78%. But this could only be achieved by altering the amounts of at least 99% of food items in the average diet. Such sweeping changes were likely to make these theoretical diets culturally unacceptable to the populations of these countries, say the authors.
Eat more fruit, vegetables and dairy products
In every country and for both men and women, eating more fruit, vegetables and starchy foods and less sugar and fat could help to reduce GHGE by 30% and would be good for our health too, say the authors.
Achieving these benefits would also require us to make changes to the amounts of animal-based foods (meat, fish, milk and dairy products) we eat. These changes would vary from country to country and according to gender. For example, people in some countries would need to eat more fish while in general, people need to eat less meat but drink more milk than most do now. More dairy products need to be eaten by men and women in Sweden and France, and by men in Finland, Italy and the UK.
When it comes to protecting the planet, GHGEs are only part of the picture, the authors point out. Future studies on sustainable diets need to take into account other factors that have an impact on the environment, such as use of fertilisers, water use, land use and biodiversity – the variety of species living on our planet.