Diet is a key lever for preserving human health and the environment. Without rapid and drastic changes in food systems, from production to consumption patterns, the environmental limits for the sustainability of ecosystems will be reached by 2050 and the incidence of chronic diseases will continue to rise. While the awareness of stakeholders seems to be strong and sustainable diets are well characterized, "food solutions" remain global (not individualized) and prospective work is based on scenarios. Indeed, no study has quantitatively assessed recent dietary changes and whether they are consistent with a transition to a more sustainable, healthier, more accessible and more environmentally friendly diet. There is an urgent need to assess, using a multi-criteria and transdisciplinary approach, the dietary transitions underway, the associated individual characteristics and to measure their impacts on health, the environment and in socio-economic terms. A better understanding of these aspects will enable us to propose actions with regard to the specific levers and barriers of population groups. The TRANSFood project aims to respond to these different issues by using a systemic approach "from field to plate" (agriculture, accessibility, consumption, etc.) based on two epidemiological studies (one cross-sectional, the other longitudinal), an experimental study and a consumer panel. More specifically, the specific objectives of the TRANSFood project include: 1) a study of dietary change trajectories over an 8-year period (covering the COVID-19 crisis and its aftermath) at the individual level (based on repeated data from the same sample) integrating food system specificities (agro-ecological and conventional farming practices). Recent changes will be assessed over an 8-year period in the NutriNet-Santé cohort in order to generate a typology of change on which subgroups of the French population (INCA3) will be located, 2) a detailed assessment of the sustainable values (economic, nutritional, health and environmental) of diets and their changes as well as the characterization of their determinants (socio-demographic, socio-economic, geographical). The environmental and health implications of these transitions will be assessed using life cycle analysis databases, a biodiversity indicator and a risk model in order to quantify the potential improvements that could be expected in the near future, 3) identification of barriers and levers and measurement of the actual individual willingness to change. A precise analysis of the levers and barriers to change will be carried out via the administration of questionnaires on the propensity to trade and via an experiment on willingness to pay. The socio-demographic (gender, age/generation, family situation), socio-economic (cost of diet, education, income etc.) and geographical (accessibility, supply) determinants of these trajectories will be highlighted, 4) the establishment of recommendations adapted to the population groups and trajectories identified by the implementation of multi-criteria models based on optimization under multiple constraints (environmental, nutritional, health, economic) which will make it possible to propose sustainable diets, according to the various characteristics, barriers and levers previously identified. The results of this project will be widely disseminated to the academic community but also to stakeholders and in particular to consumers.

It is widely recognised that, at present, dietary patterns and lifestyles in most industrialized countries are not optimal for sustaining health. Another key challenge for public health is the sustainability of the food systems, including energy, land and water use, ecosystem preservation and biodiversity as well as climate change. Some alternative production systems are now recognised, especially for their reduced environmental impact. In this context, organic food production has markedly increased during the last decade: up to 3-20% (mean 5.1%) of agricultural land in the European Union and around 0.6 % in the USA. This is largely driven by consumer attitudes and growing demand for those specific foodstuffs. There was a yearly increase in production above 10% reaching a worldwide production of 700 million T food/y in 2012and a market share of about 60 billion US $/y. In 2010, the countries with the largest markets were the United States, Germany and France. Little information is available on large populations regarding the determinants, motivations, socio-demographic profiles, actual food/nutrient intakes and biological and toxicological status of different kind of organic food consumers (occasional, regular and heavy consumers) and differences with consumers of conventional foods. We plan to conduct a project which will provide a comprehensive description of subjects according to their level of organic food consumption. This proposal is based on the NutriNet-Santé study, a large-scale web-based observational epidemiologic study launched in may 2009, with self-reported and biological data collected at the individual level. This project and the achievement of its objectives will rely on a multidisciplinary partnership involving epidemiologists, nutritionists, biologists, economists, specialists in environmental impact evaluation and analytical chemists. The first objective is to quantitatively assess food consumption by source, i.e. organic or conventional. The part of organic food in the whole diet will be estimated at the individual level. A comprehensive description of nutrient intakes, food consumption, dietary patterns and adherence to nutritional guidelines according to the level of organic food consumption will be provided. Sociodemographic, psychological and economic profiles (for evaluation of the cost of the diet) of organic food consumers will be investigated as well as motives as regards sustainable diet purchases. The second objective is to estimate the production-related environmental impact of organic and conventional food consumption and to describe the level of organic food consumption through different indicators. A compilation of the current knowledge with respect to contaminants in organic and conventional food will allow quantifying contaminant intake according to organic food consumption. A third objective will be to select 2 distinct sub-groups according to their level of organic food consumption to investigate nutritional (vitamin and minerals) and toxicological status (pesticide residues) as well as urinary metabolomic profiles based on biological data collected in a subsample of the Nutrinet-Santé Study. The sub-group selection will account for matching covariates, in particular quality of the diet. This project will produce valuable information as regards differential phenotypes according to organic food consumption and will advance knowledge in the context of organic food promotion.