A large US-UK analysis shows that eating more plant-forward meals and fewer animal-source foods is associated with a lower death risk and smaller environmental footprint, offering evidence that what is good for people can also be good for the planet.

Study: Planetary Health Diet and risk of mortality and chronic diseases: Results from US NHANES, UK Biobank, and a meta-analysis. Image Credit: udra11 / Shutterstock

Study: Planetary Health Diet and risk of mortality and chronic diseases: Results from US NHANES, UK Biobank, and a meta-analysis. Image Credit: udra11 / Shutterstock

In a recent study published in the journal Science Advances, researchers examined the associations between higher adherence to the Planetary Health Diet (PHD) and all-cause and cause-specific mortality in two cohorts. They synthesized prior evidence on major chronic diseases in a meta-analysis. They also investigated the environmental impacts of reported diets.

Background

One in three deaths worldwide is linked to diet, while food systems generate 30% of human-caused greenhouse gases. Households feel this in rising grocery bills, climate anxiety, and nutrition advice.

The PHD, outlined by the EAT-Lancet Commission on Healthy Diets from Sustainable Food Systems, promotes plant-forward meals with modest amounts of animal-source foods to safeguard human and planetary health. Early evidence suggests health and environmental benefits; however, estimates vary by country, measurement, and outcome. 

Clinicians, families, and policymakers need guidance that converts into meals and policies. Further research is required to test causal effects and implement solutions on a scalable basis across diverse populations.

About the study

Researchers combined two prospective cohorts to assess mortality and performed a meta-analysis to evaluate the incidence of chronic diseases. In the United States National Health and Nutrition Examination Survey (NHANES, 1999–2018), adults aged 20 and above with plausible energy intake were eligible; in the United Kingdom Biobank (UKB), adults aged 40–69 who completed at least two 24-hour diet recalls were retained.

PHD scores (0–140) were computed from fourteen EAT-Lancet components and standardized to 2,500 kilocalories per day using the Food Patterns Equivalents Database (FPED) conversions; in NHANES, scores were based on the first-day 24-hour recall, while in UK Biobank, intakes were averaged across at least two 24-hour WebQ recalls. 

Researchers noted that total energy intake was slightly higher among those who scored well on the diet, suggesting that food quality may matter more than calories alone.

Diet-related greenhouse gas emissions were estimated using life cycle assessment (LCA) sources, the Diet-Related Food Impacts on the Environment Database for NHANES, and a United Kingdom inventory for UKB, and expressed as kilograms of carbon dioxide equivalent (CO2eq).

Mortality outcomes relied on the International Classification of Diseases, Ninth and Tenth Revisions (ICD-9/ICD-10), with linkage to the National Death Index (NDI) in the United States and the National Health Service (NHS) registries in England, Wales, and Scotland.

Cox proportional-hazards models estimated hazard ratios (HRs) and 95% confidence intervals (CIs) across PHD quartiles, adjusting sequentially for demographics, behaviors, socioeconomic status, medical history, and body mass index (BMI), along with multiple sensitivity analyses, dose-response splines, and prespecified subgroup analyses. Missing covariates were multiply imputed under chained equations where necessary.

Study results

In the US NHANES study of nearly 43,000 adults (average age 47), people who scored highest on the Planetary Health Diet tended to have a lower body weight, more education, and were less likely to smoke. Over the follow-up period, about 6,800 deaths were recorded. Those with the highest diet scores had about a 23% lower risk of death from any cause, a 19% lower risk of death from heart disease, and a 19% lower risk of death from other causes compared to those with the lowest scores.

Nonlinear modeling suggested an overall inverse trend for all-cause mortality. In sensitivity analyses that excluded early deaths, the inverse association with cancer mortality was observed, whereas the associations with heart disease mortality attenuated in some models.

In the UK Biobank study of more than 125,000 adults (average age 57), nearly 6,900 deaths occurred during follow-up. People with the highest Planetary Health Diet scores had a 16% lower risk of death from any cause, a 16% lower risk of death from cancer, and a striking 61% lower risk of death from respiratory diseases compared to those with the lowest scores. The more closely participants followed the diet, the lower their risk of dying from all causes and cancer.

Results were precise across multiple sensitivity analyses with consistent direction and magnitude. The authors note that cancer mortality coding differed between cohorts, which may partly explain the variation across datasets.

Environmental analyses revealed that red meat and dairy products contributed the largest shares of diet-related greenhouse gas emissions in both cohorts, with saturated and unsaturated fats also being prominent in the UKB. Diets in higher PHD quartiles were associated with lower overall greenhouse gas footprints. The authors caution that these life cycle assessment–based estimates have limitations and are specific to each country.

When researchers combined results from 37 studies involving more than 3.2 million people, those who most closely followed the Planetary Health Diet had a 21% lower risk of dying from any cause, a 17% lower risk of dying from cancer, and a 17% lower risk of dying from cardiovascular disease compared to those with the lowest adherence. They also had lower risks of developing several major conditions, including colorectal cancer (13% lower risk), lung cancer (32% lower), cardiovascular disease (17% lower), coronary heart disease (17% lower), stroke overall (16% lower), and diabetes (26% lower). The diet showed no clear effect on ischemic or hemorrhagic stroke separately.

Across cohorts, people with higher PHD scores tended to be older and more often female, with healthier behaviors and BMI profiles. Unlike some healthy-eating indices, higher adherence was associated with slightly higher total energy intake in certain analyses, a pattern that warrants further investigation into food choice quality, energy density, and satiety within sustainable dietary patterns in future randomized cohorts.

Conclusions

Greater adherence to the PHD was associated with lower all-cause mortality in both cohorts, with additional reductions in cancer and respiratory mortality in UKB and in heart-disease mortality in NHANES, alongside smaller diet-related greenhouse gas footprints.

For individuals, the pattern maps onto choices such as favoring legumes, whole grains, fruits, vegetables, and nuts while limiting red meat and high-impact fats.

For communities and health systems, the findings support policies that align nutrition with climate action. Because the analyses are observational and rely on self-reported diet, residual confounding and measurement error remain possible, and randomized trials in diverse populations would strengthen causal inference.

Journal reference:

Wang, Y., Pan, D., Zhang, C., Xu, D., Lu, Y., Yin, S., Wang, P., Xia, J., Yu, J., Dong, L., & Sun, G. (2025). Planetary Health Diet and risk of mortality and chronic diseases: Results from US NHANES, UK Biobank, and a meta-analysis. Sci. Adv.11 (36). DOI:10.1126/sciadv.adq5147, https://www.science.org/doi/10.1126/sciadv.adq5147