Healthy and sustainable diet: how to meet both nutritional needs and climate challenges?

Apr 10, 2024
Sébastien Bouley

The agriculture and food system accounts for 34% of greenhouse gas (GHG) emissions. France has committed to reducing GHG emissions by 46% by 2025. A joint study by the French Society of Nutrition (SFN) and the Climate Action Network (RAC) carried out by Nicole Darmon showed that a 50% reduction in meat consumption combined with an increase in the consumption of adequate vegetables reduces the carbon impact by 35% while satisfying nutritional recommendations for adults.

Sustainable food:

According to ADEME’s definition, sustainable food is the set of food practices that aim to feed human beings in sufficient quality and quantity, today and tomorrow, while respecting the environment, by being economically accessible and remunerative throughout the food chain. It therefore has 4 dimensions: environmental, economic, nutritional and socio-cultural.

Climate challenge:

According to current estimates, global warming is expected to reach 1.5°C between 2030 and 2052 based on current trends. It is important to take action to limit global warming. To do this, we need to reduce greenhouse gas (GHG) emissions across all sectors, including food systems. The agriculture and food system accounts for 34% of global greenhouse gas emissions due to greenhouse gas emissions from ruminants and nitrous oxide emissions from fertilizers and livestock manure. According to the GIEC report, it would be possible to reduce the share of GHGs generated by food systems by 44% by, among other things, decreasing the consumption of food products of animal origin.

Meeting climate issues and nutritional recommendations:

To what extent can we reduce the consumption of animal products without exposing the consumer to the risk of nutritional deficiencies? is the question to consider. The requirements for vitamin B12, iodine, calcium, EPA-DHA and bioavailable iron can be difficult to meet when the consumption of animal proteins is reduced too much, according to the mathematical models based on current consumption data. In addition, given the ageing of the French population, care must be taken to ensure that the protein and amino acid needs of older people are well met.

Existing models and scenarii:

Research has been done to define what a sustainable diet would be. This work can be classified into 4 main categories:

  1. the proposal of theoretical diets that are supposed to be more sustainable and designed on the basis of a priori considerations (e.g. the EAT-Lancet reference diet, substitution of animal products by plant products, etc.), with a posteriori verification of the potential interest of these diets in the light of various criteria in sustainability,
  2. the assessment of the sustainability of existing diets based on individual food consumption surveys and the analysis of associations between different sustainability criteria,
  3. the identification of diets that are more sustainable than others within existing diets, with a view to isolating, among existing diets, those that best reconcile different requirements of sustainability,
  4. the design of theoretical diets by a multi-criteria approach without a priori based on the technique of optimization under constraints: this method makes it possible to go further than the existing one, by generating diets that meet several requirements on different dimensions of sustainability.

Mathematical optimization under constraints was used because this technique makes it possible to simultaneously integrate many requirements corresponding to the different dimensions of durability. Nicole Darmon used this method to identify how the PNNS4 recommendations could evolve to take into account the need to reduce the environmental impact, i.e. to reduce adult meat consumption by 50%. As a starting point, the average diet of more than 2,000 adults (2121 adults, including 1234 women and 887 men) was considered from the INCA 3 survey (2014-2015). A total of 17 models were tested depending on whether the reduction of the carbon impact was increased and whether a maximum daily intake of 2 or 3 dairy products was considered.

Healthy and sustainable food:

The results show that a 50% reduction in meat consumption would reduce the carbon impact by 20 to 50% depending on the changes associated with meat reduction. The compromise that seems the most acceptable from a cultural, environmental and nutritional adequacy point of view is to set the level of reduction of the environmental impact at (-35%). To achieve this objective, the recommendations of PNNS 4 would evolve by:

– Recommend eating no more than 450g of meat per week, including all meats, poultry and processed meats. The consumption of cold meats(“charcuterie”) should not exceed 150g per week as currently in the recommendations of the PNNS4.

– Recommend consuming 2 small handfuls of salt-free nuts, i.e. 25 to 30g per day, with a preference for walnuts.

– Recommend consuming 65 to 100g (baked weight) per day of legumes per day.

Dietary recommendations that evolve as part of a sustainable diet with a reduction in carbon impact of (-35%) Current PNNS 4 New dietary recommendations
For all meats ≤ 500g/week of meat excluding poultry. Prefer poultry.

And

≤ 150g/week of cold cuts. Prefer white ham

≤ 450g/week for all meat, poultry and processed meats, including a maximum of 150g/week for cold cuts
For legumes At least 2 times a week 65 à 100 g (baked weight) par jour
For nuts 1 small handful of salt-free nuts, i.e. 15 per day 2 small handfuls of salt-free nuts, i.e. 25 to 30g per day, with a preference for walnuts

 

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