Associations between dietary greenhouse gas emissions, mortality, and chronic disease risk: a prospective cohort study in Sweden

• Dietary GHGE linked to higher risk of diabetes in Swedish adults • Non-linear associations found for all-cause and cardiovascular mortality • Cancer mortality was higher among those with the highest dietary GHGE • Multiple GHGE modelling methods applied, revealing methodological sensitivity • Climate-friendly diets may offer health co-benefits alongside sustainability The global food system is a major contributor to climate change, accounting for about one-third of human-induced greenhouse gas emissions (GHGE). Shifting toward plant-based diets offers potential benefits for both planetary health and chronic disease prevention. However, epidemiological evidence linking dietary GHGE to health outcomes remains limited and inconsistent. To examine the associations between dietary GHGE and the risk of all-cause and cause-specific mortality, cardiovascular disease (CVD), and type 2 diabetes in a large Swedish cohort. This prospective cohort study included 22,388 adults (45-73 years) from the Malmö Diet and Cancer study. Dietary intake was assessed through a validated modified diet history method and linked to GHGE estimates using life cycle assessment data. Cox proportional hazards models were used to assess associations between GHGE and disease outcomes, adjusting for sociodemographic and lifestyle factors. Over a mean follow-up of 28.5 years, 11,213 deaths, 5,322 CVD cases, and 4,324 diabetes cases were documented through registers. Higher GHGE were consistently associated with higher risk of diabetes (p>0.001). For all-cause and CVD mortality, moderate positive associations were observed, particularly among participants with very high GHGE. When participants who reported substantial dietary changes prior to baseline were excluded, a significant linear association was observed for cancer mortality and CVD incidence. Diets with higher climate impact were associated with adverse health outcomes, especially diabetes incidence. These findings suggest that climate-friendly diets may also confer health benefits. Future studies should transparently report GHGE modelling approaches and clarify the roles of specific dietary components in improving both health and environmental outcomes.