Background: Studies investigating diet-related environmental impacts have rarely considered the production method of the foods consumed. The objective of the present study, based on the NutriNet-Santé cohort, was to investigate the relationship between a provegetarian score and diet-related environmental impacts. We also evaluated potential effect modifications on the association between a provegetarian score and the environmental impacts of organic food consumption. Methods: Food intake and organic food consumption ratios were obtained from 34,442 French adults using a food frequency questionnaire, which included information on organic food consumption for each group. To characterize the overall structure of the diets, a provegetarian score was used to identify preferences for plant-based products as opposed to animal-based products. Moreover, three environmental indicators were used to assess diet-related environmental impacts: greenhouse gas (GHG) emissions, cumulative energy demand (CED), and land occupation. Environmental impacts were assessed using production life cycle assessment (LCA) at the farm level. Associations between provegetarian score quintiles, the level of organic food consumption, and environmental indicators were analyzed using ANCOVAs adjusted for energy, sex, and age. Results: Participants with diets rich in plant-based foods (fifth quintile) were more likely to be older urban dwellers, to hold a higher degree in education, and to be characterized by an overall healthier lifestyle and diet. A higher provegetarian score was associated with lower environmental impacts (GHG emissions_Q5vsQ1 = 838/1,664 kg CO_2eq/year, −49.6%, P < 0.0001; CED_Q5vsQ1 = 4,853/6,775 MJ/year, −26.9%, P < 0.0001; land occupation_Q5vsQ1 = 2,420/4,138 m²/year, −41.5%, P < 0.0001). Organic food consumption was also an important modulator of the relationship between provegetarian dietary patterns and environmental impacts but only among participants with diets rich in plant-based products. Conclusion: Future field studies should endeavor to integrate all the components of a sustainable diet, i.e., both diet composition and production methods.

In the current context of unsustainable food systems, we aimed to develop and validate an index, the sustainable diet index (SDI), assessing the sustainability of dietary patterns, including multidimensional individual indicators of sustainability. Based on the FAO’s definition of sustainable diets, the SDI includes seven indicators categorised into four standardised sub-indexes, respectively, environmental, nutritional, economic and sociocultural. The index (range: 4–20) was obtained by summing the sub-indexes. We computed the SDI for 29 388 participants in the NutriNet-Santé cohort study, estimated its validity and identified potential socio-demographic or lifestyle differences across the SDI quintile. In our sample, the SDI (mean=12·10/20; 95 % CI 12·07, 12·13) was highly correlated to all the sub-indexes that exerted substantial influence on the participants’ ranking. The environmental and economical sub-indexes were the most and less correlated with the SDI (PearsonR²0·66 and 0·52, respectively). Dietary patterns of participants with a high SDI (considered as more sustainable) were concordant with the already published sustainable diets. Participants with high SDI scores were more often women (24 %), post-secondary graduates (22 %) and vegetarians or vegans (7 %), without obesity (16 %). Finally, the SDI could be a useful tool to easily assess the sustainability-related changes in dietary patterns, estimate the association with long-term health outcomes and help guide future public health policies.

Organic food consumption has steadily increased over the past decade in westernized countries. The aim of this study, based on observational data, was to compare some sustainability features of diets from consumers with varying levels of organic food. The diet sustainability among 29,210 participants of the NutriNet-Santé study was estimated using databases developed within the BioNutriNet project. Four dimensions (nutrition, environment, economy, and toxicology) of diet sustainability were assessed using: 1) nutritional indicators through dietary intakes and dietary scores, and BMI; 2) environmental indicators (greenhouse gas emissions, cumulative energy demand, and land occupation); 3) economic indicators via diet monetary costs; and 4) estimated daily food exposures to 15 pesticides. Adjusted means (95% CI) across weighted quintiles of organic food consumption in the diet were estimated via ANCOVA. Breakdown methods were used to disentangle the contribution of the production system (organic compared with conventional) from the dietary pattern in the variation of diet-related environmental impacts, monetary costs, and pesticide exposure, between the 2 extreme quintiles. Higher organic food consumption was associated with higher plant-food and lower animal-food consumption, overall nutritional quality (higher dietary scores), and lower BMI. Diet-related greenhouse-gas emissions, cumulative energy demand, and land occupation gradually decreased with increasing organic food consumption, whereas total diet monetary cost increased. Diet exposure to most pesticides decreased across quintiles. Diets of high organic food consumers were generally characterized by strong nutritional and environmental benefits. The latter were mostly driven by the low consumption of animal-based foods, whereas the production system was responsible for the higher diet monetary costs, and the overall reduced dietary pesticide exposure.

Mediterranean diets are promising sustainable food models and the organic food system may provide health and environmental benefits. Combining the two models could therefore be a favourable approach for food sustainability. The aim of this study was to draw up a comparative description of four diets differing in the level of organic foods consumption and the adherence to the Mediterranean diet, using multidisciplinary indicators to assess the sustainability of these diets. Four groups of participants were defined and compared, combining the proportion of organic food in their diet (Org versus Conv) and the adherence to the Mediterranean diet (Med versus NoMed). Conv–NoMed: Conventional consumers and non-Mediterranean diet followers; Conv–Med: Conventional consumers and Mediterranean diet followers; Org–NoMed: Organic consumers and non-Mediterranean diet followers; Org–Med: Organic consumers and Mediterranean diet followers. The adherence to nutritional recommendations was higher among the Org–Med and Conv–Med groups compared to the Conv–NoMed group (using the mPNNS-GS (modified-Programme National nutrition santé guidelines score/13.5 points): 9.29 (95% confidence intervals (CI) = 9.23–9.36) and 9.30 (95% CI = 9.24–9.35) versus 8.19 (95% CI = 8.17–8.22)) respectively. The mean plant/animal protein intake ratio was 1.38 (95% CI = 1.01–1.74) for the Org–Med group versus 0.44 (95% CI = 0.28–0.60) for the Conv–NoMed group. The average cost of the diet of Org–Med participants was the highest: 11.43 €/day (95% CI = 11.34–11.52). This study highlighted the importance of promoting the Mediterranean diet combined with organic food consumption for individual health and environmental aspects but challenges with regard to the cost remain.

Improving the sustainability of current food systems may prevent future public health, environmental, and social concerns. Our objective was to investigate the associations between sustainable dietary patterns, assessed using the Sustainable Diet Index (SDI), and the risk of obesity, overweight, and weight gain in French adults, with a prospective design. In 2014, the SDI was computed among 15,626 participants of the NutriNet-Santé study (of whom 76% were women) using data collected within the BioNutriNet project. The SDI ranges from 4 (lowest sustainability) to 20 points and includes 4 subindexes representing the 4 pillars of a sustainable diet. Longitudinal data of weight and height were collected yearly from 2014 to 2018. We used mixed models to estimate the associations between sex-specific quintiles (Qs) of the SDI and weight change and Cox proportional hazard models with different levels of adjustments to assess the association between sex-specific Qs of the SDI and risk of obesity and overweight (mean follow-up time: 2.8 y). At baseline, a higher percentage of participants with overweight was observed in the first SDI Q, reflecting the lowest sustainable dietary patterns (Q1), than in Q5 (29.83% compared with 12.71%). Compared with Q5, a slight increase (at the population level) of almost 160 g/y was observed in Q1, whereas weight remained relatively stable among participants in other Qs. In total, 281 incident cases of obesity and 777 cases of overweight were identified during the follow-up. Participants in Q1 had a higher risk of obesity and overweight than participants in Q5 (HR comparing Q1 with Q5: 4.03; 95% CI: 2.42, 6.10; P-trend < 0.001; and HR comparing Q1 with Q5: 1.49; 95% CI: 1.13, 1.95; P-trend < 0.001, respectively). The findings support a potential protective role for more sustainable diets to prevent the risk of weight gain, overweight, and obesity.This trial was registered at clinicaltrials.gov as NCT03335644.