Doctor: Louise Seconda

Title: Identification of new dietary pattern : Estimation of environmental and individual impacts

Supervisor: Emmanuelle Kesse-Guyot

Doctoral school: ED 146 Doctoral school Galilée, University Sorbonne Paris Nord

Date of thesis defense: 10/2019

Jury: Olga Davidenko, Pierre Lombrail

Thesis summary:

In order to not exceed the environmental planetary boundaries and ensure a good life for future generations, the food systems have to be sustainable. This thesis proposes to assess the sustainability of dietary patterns by integrating environmental, economic or socio-cultural and nutrition indicators.This thesis is based on data from the NutriNet-Santé cohort and those collected in the BioNutriNet project. In particular, during the BioNutriNet project data on the environmental impacts of food production by distinguishing between organic and conventional production methods, as well as food prices by also distinguishing production methods and places of purchase were collected. We proposed three approaches to evaluate the sustainability of dietary patterns within the cohort: an approach based on greenhouse gas emissions related to the production of diets, a more exploratory approach leading to a typology and finally an a priori approach consisting of creating an index to assess the sustainability of French diets. In a second step, we assessed the associations between diets identified as sustainable and the risk of obesity, overweight, cancer and/or cardiovascular disease and with body weight gain. Finally, from the data, we proposed more or less conservative solutions for sustainable diets using optimization.We were able to identify different dietary patterns according to their sustainability. The approach chosen has little impact on the structure of the most sustainable diets. The proportion of food groups in these most sustainable diets were almost 50% fruit and vegetables, 15% starch, 10% dairy products, 3% meat and 2% fish, and 4% soybean products. The most important difference between the three approaches relies on the contribution of organic foods to diets. We have observed a decrease in the risk of obesity, overweight and cancer for those who adopted the most sustainable dietary patterns. Finally, solutions from the optimization showed that from the least to the most disruptive scenarios, the contributions of fruits, vegetables, starch and soybean increase while those of animal foods and fatty and sweet foods decrease. Trends were independent of the level of vegetal-based food in the initial diets. Several solutions could be found to meet environmental challenges, while remaining economically accessible and covering the main nutritional needs. The choice of scenarios will have to be discussed in the light of the effort that we want to make on food in relation to other areas.Finally, the work carried out during this thesis showed that it is possible to identify and propose diets on good nutritional quality and to meet in part to environmental and public health emergencies while trying to ensure their economic accessibility and acceptability. In the context of unsustainable food systems and an increasing prevalence of chronic diseases, these results may be of major interest to justify the integration of sustainability into agricultural and public health policies.

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