Highlight
The recent EPIC-Norfolk prospective cohort study reveals that high adherence to the planetary health diet (PHD) substantially lowers the incidence of type 2 diabetes (T2D) by about 32% and concurrently reduces dietary greenhouse gas (GHG) emissions by approximately 18%. These findings bolster the dual benefit of this diet pattern for chronic disease prevention and environmental sustainability.
Study Background
Type 2 diabetes remains a major global public health challenge, driven largely by modifiable lifestyle factors including diet. Concurrently, food systems are among the largest contributors to greenhouse gas emissions, implicating diet as a key intersectional factor linking human health and planetary sustainability. The planetary health diet (PHD), conceptualized by the EAT-Lancet Commission, aims to optimize human nutrition while minimizing environmental harm. However, longitudinal epidemiological evidence linking adherence to the PHD with incident T2D and the associated carbon footprint has so far been limited.
Study Design
The EPIC-Norfolk study is a UK-based prospective cohort involving 23,722 adults (55% female), with a mean baseline age of 59.1 years. Dietary intake was measured through repeated food frequency questionnaires administered at three time points between 1993 and 2011, allowing for time-varying assessment of PHD adherence. The PHD score ranged from 0 to 140 points, reflecting adherence across 13 food groups plus two nutrient domains, emphasizing increased consumption of plant-based foods and limited animal products.
Incident T2D cases were ascertained over a mean follow-up of 19.4 years (SD 6.8), with 3,496 new cases identified across 461,086 person-years. Cox proportional hazards regression models with time-updated covariates (including socio-demographics, behavioral factors, total energy intake, adiposity measures, and prior cardiovascular or cancer diagnoses) were used to estimate hazard ratios (HRs) for T2D by PHD adherence quintiles. Additionally, linear regression models evaluated the association between PHD adherence and estimated dietary GHG emissions.
Key Findings
Participants in the highest quintile of PHD adherence (score range 85.7–117.8) had a significantly lower risk of developing T2D compared to those in the lowest quintile (33.9–68.4 points), with an adjusted HR of 0.68 (95% confidence interval [CI]: 0.61 to 0.76), indicating a 32% relative risk reduction. This association remained robust after adjustment for multiple confounders, suggesting an independent protective effect of the PHD.
The estimated population attributable fraction (PAF) demonstrated that 12.3% (95% CI: 9.2% to 15.3%) of incident T2D cases could potentially be prevented if adherence to the PHD was improved to levels above the 80th percentile in the population.
Regarding environmental impact, those in the highest adherence group exhibited approximately 18.4% lower dietary GHG emissions compared to the lowest adherence group (β coefficient: −18.4%, 95% CI: −19.3% to −17.5%), underscoring significant ecological benefits of the PHD.
Notably, the observational design imposes limitations, including potential residual confounding and measurement error in dietary assessment. However, the large sample size, repeated dietary assessments, and comprehensive adjustment strengthen the validity of the findings.
Expert Commentary
Dietary strategies that concurrently target chronic disease prevention and climate change mitigation are urgently needed. The EPIC-Norfolk findings provide valuable real-world epidemiological evidence supporting the PHD’s role in reducing T2D incidence while lowering environmental footprints. This aligns with mechanistic and intervention data highlighting the benefits of plant-forward diets rich in fiber, whole grains, and unsaturated fats for insulin sensitivity and weight control.
While randomized controlled trials ultimately are required to establish causality and elucidate mechanistic pathways, the consistency of benefit across diverse populations supports integration of the PHD principles into public health policies. Moreover, these results complement emerging guidelines recommending reduced consumption of red and processed meats alongside increased plant-based foods for metabolic and planetary health.
Challenges remain in translating such diets into accessible, culturally appropriate, and economically feasible recommendations at the population level. Further research is warranted to explore barriers and facilitators to adherence and to evaluate impact on other metabolic outcomes and sustainability metrics.
Conclusion
The EPIC-Norfolk prospective cohort study demonstrates that higher adherence to the planetary health diet is associated with a substantially reduced risk of incident type 2 diabetes and markedly lower dietary greenhouse gas emissions. These dual benefits reinforce the PHD as an actionable and scalable dietary framework to improve population metabolic health and advance environmental sustainability goals. Integrating the PHD into clinical and public health nutrition guidance may contribute to alleviating the growing burden of type 2 diabetes while addressing climate change.
Funding and Clinical Trials Information
The study was conducted under EPIC-Norfolk, supported by grants from national health research councils and environmental agencies (detailed grant information available in the original publication). The observational nature precluded clinical trial registration.
References
- Sowah SA, Imamura F, Ibsen DB, Monsivais P, Wareham NJ, Forouhi NG. The association of the planetary health diet with type 2 diabetes incidence and greenhouse gas emissions: Findings from the EPIC-Norfolk prospective cohort study. PLoS Med. 2025 Sep 16;22(9):e1004633. doi: 10.1371/journal.pmed.1004633. PMID: 40956993; PMCID: PMC12440362.
