If you don’t want to do it for the planet, at least do it for yourself! Scientists from Harvard HT Chan School of Public Health found that people in the United States who eat a more environmentally sustainable diet had a 25% lower risk to die during a follow-up period of over 30 years compared to those with a less sustainable diet.

The new study builds on previous research that identified foods that are beneficial for health and the environment as well as foods that could be harmful to both. The findings show how eating more planet-friendly food could help lower the risk of death from a wide array of causes, such as respiratory diseases, heart disease, and cancer.

The planetary health diet is a concept created by the EAT-Lancet Commission in a report back in 2019. It’s essentially a healthy and sustainable diet that focuses on fruits, nuts, unsaturated oils, and non-starchy vegetables such as tomatoes and broccoli. This contrasts with foods such as red and processed meat and eggs, which are more impactful to the environment — and often bad for your health.

To highlight these issues, the researchers suggest a new metric.

“We proposed a new diet score that incorporates the best current scientific evidence of food effects on both health and the environment,” Linh Bui, study author from Harvard, said in a media statement. “The results confirmed our hypothesis that a higher Planetary Health Diet score was associated with a lower risk of mortality.”

A healthy and sustainable diet

Back in 2019, the EAT-LanceT Commission developed the world’s first scientific targets for healthy and sustainable food systems, including a planetary health diet – created to meet nutritional needs and promote health while staying within planetary boundaries. Adopting it would require doubling the average consumption of fruits, vegetables, and nuts.

For their study, the researchers surveyed 100,000 participants in the US. The data set included over 47,000 deaths during a 30-year follow-up period from 1986-2018. Overall, the findings, presented at the American Society for Nutrition conference, showed that participants with a good planetary health diet had a lower risk of mortality.

“As a millennial, I have always been concerned about mitigating human impacts on the environment,” said Bui in a media statement. “A sustainable dietary pattern should not only be healthy but also consistent within planetary boundaries for greenhouse gas emissions and other environmental parameters.”

Using the collected data, the researchers created a Planetary Health Diet Index (PHDI) and ranked participants based on the healthiness and sustainability of their diets. They then used this to evaluate the link between the scores and the participants’ health outcomes. Those with the top PHDI scores had a 25% lower risk of death compared to those with the lowest scores.

The researchers then looked a bit closer into more specific causes of death. Those with higher PHDI scores were associated with a 15% lower risk of death from cancer or cardiovascular diseases, a 20% lower risk from neurogenerative disease and a 50% lower risk from respiratory diseases. Overall, eating healthy and sustainably pays off.

Looking ahead, they wish their index can be used as a tool for policymakers and public health practitioners to improve human health while addressing climate change. Nevertheless, they acknowledge that the PHDI doesn’t take into account challenges people could have in following a sustainable diet, such as the socioeconomic availability of food.