Diets that harm the planet also raise the risk of cancer, heart disease, and diabetes

A large French cohort study reveals that eating patterns with lower environmental footprints not only protect the planet but also cut the risk of major chronic diseases, a double win for people and the planet.

Study: Association between dietary environmental pressures and major chronic diseases: assessment from the prospective NutriNet-Santé cohort. Image Credit: metamorworks / Shutterstock

In a recent study published in The Lancet Regional Health, researchers investigated links between diet-related environmental pressures and human health.

The study leveraged a large-scale prospective study of over 34,077 French adults and found that for each one-standard-deviation increase in the composite EPI, the risk of developing cancer (HR 1.15 [95% CI 1.03–1.28]), coronary heart disease, and type 2 diabetes (HR 1.50 [1.29–1.73]) increased significantly. No significant association was observed with stroke or all-cause mortality.

These findings suggest that diets with lower overall environmental pressures are associated with better health outcomes and that sustainable food systems are critical to planetary and public health.

The Co-Benefits of Sustainable Diets for Health and Environment

“Co-benefits” refers to the increasingly popular concept that postulates that a single action (e.g., consciously choosing sustainable foods over their unsustainable alternatives) can simultaneously benefit both human health and the environment.

The concept has now become a central topic in climate and health discussions, with decades of research suggesting that dietary patterns are a significant factor in the rising global burden of chronic diseases, including cancer, cardiovascular disease (CVD), and diabetes (particularly type 2 diabetes [T2D]).

Global Food Systems as Drivers of Environmental Degradation

Unfortunately, recent research has found that the current global agri-food system is a primary driver of environmental damage, contributing significantly to greenhouse gas emissions (GHGe), land degradation, and freshwater use.

Comparative studies examining the environmental impacts of different food products have shown that plant-based diets are generally better for the planet than their animal-derived counterparts. However, most of these studies have focused on only one or two environmental indicators, such as GHGe, limiting their generalizability in the broader sustainability context.

Need for Comprehensive Assessment of Diet-Related Environmental Pressures

A comprehensive investigation of a broad spectrum of environmental pressures and their associations with human health would provide policymakers and public health agencies with the knowledge required to optimize sustainable dietary advice, thereby improving outcomes both for the environment and supporting human health.

However, not all environmental indicators were aligned with lower health risk: higher water use was linked to lower cancer risk, and higher ecological infrastructure was positively associated with several disease risks.

Study Design Using the NutriNet-Santé Cohort

The present study addressed this knowledge gap by leveraging prospective cohort data from the NutriNet-Santé cohort, an extensive, web-based population study in France. Screening of NutriNet-Santé cohort participant data identified 34,077 adult participants who met study requirements (age> 15). The study critically included long-term health data (median follow-up time = 8.39 years).

Dietary Data Collection and Environmental Impact Scoring

Diet was measured once at baseline in 2014 using a 264-item organic-capable Food Frequency Questionnaire (Org-FFQ), which logged participants’ dietary habits and how often those foods were organic versus conventionally produced.

Additionally, participants’ sociodemographic information (for statistical model correction) and detailed medical histories (for long-term health outcomes analyses) were collected. This data was then merged with environmental databases to calculate the impact of each person’s diet across six distinct indicators:

1. GHGe
2. Cumulative energy demand
3. Land occupation
4. Water use (primarily for irrigation)
5. Pesticide use (treatment/application frequency)
6. Ecological infrastructures (biodiversity impact)

Finally, the outcomes of these individual indicators were combined into a single synthetic score, the Environmental Pressures Index (EPI), with higher scores indicating greater, more harmful environmental impact.

Weighted multivariable Cox proportional hazards models with extensive covariate adjustment, proportional-hazards checks via Schoenfeld residuals, dose–response assessed using restricted cubic splines, and marginal structural models in sensitivity analyses were leveraged to elucidate if a high EPI score was associated with a participant’s future risk of developing chronic diseases.

Environmental Pressures Strongly Correlated with Chronic Disease Risk

Study findings revealed a clear and positive association between the environmental and health impacts of different foods; a diet worse for the environment was also observed to result in suboptimal health outcomes.

Specifically, statistical models revealed that for every one-standard-deviation increase in an individual’s EPI score, their risk of developing cancer (any) rose by 15% (HR 1.15). The results were even more stark for metabolic and cardiovascular health: the risk of coronary heart disease and T2D both increased by 50% (HR 1.50) for every SD increase.

No statistically significant associations were found for stroke or all-cause mortality during the follow-up period.

Dietary Patterns Associated with High and Low Environmental Pressure

The study further established patterns between diets and health outcomes; participants with the highest-pressure (high-EPI) diets were observed to consume significantly more red meats (pork, beef, and lamb), poultry, and processed meats.

Conversely, those on the lowest-pressure (low-EPI) diets ate more whole grains, fruits, and vegetables, aligning closely with sustainable eating plans like the increasingly popular EAT-Lancet diet.

Higher pesticide treatment frequency was positively associated with cancer, CVD, and T2D risks, whereas higher water use, reflecting greater fruit and vegetable intake, was linked to lower cancer risk. Ecological infrastructure scores, capturing biodiversity-related pressures, showed paradoxical positive associations with several chronic diseases. Although low-EPI diets were not strictly vegetarian, they tended to be more plant-rich and less reliant on animal-based foods, reflecting broader sustainable dietary patterns.

The study also accounted for farming methods, distinguishing between organic and conventional production, ensuring that these were integrated into environmental impact estimates. Stroke analyses were acknowledged to have lower statistical power due to fewer incident cases, potentially limiting precision.

Broader Implications for Public Health and Sustainable Food Systems

The present study provides strong, comprehensive evidence supporting a “win-win” scenario: diets with a low overall environmental footprint are associated with significant health benefits. While the study was likely biased to include health-conscious volunteers with better overall dietary choices than the population mean, these findings reinforce the idea that sustainable food systems are a critical component of public health.

The study evaluated environmental pressures rather than labelling diets as vegetarian or non-vegetarian, underscoring that the health and environmental advantages arise from overall dietary composition rather than categorical diet type. By demonstrating the consistency of findings in sensitivity analyses and marginal structural models, the authors reinforced the robustness of these associations.