Eating a healthy, sustainable diet can result in substantial benefits to both human and planetary health, according to new research (1).

The first-of-its-kind study looked at the impact of adhering to the Planetary Health Diet (PHD) – which emphasises plant foods (such as whole grains, legumes, nuts and vegetables), but allows for modest consumption of meat and dairy foods.  

The researchers, from the Harvard T.H. Chan School of Public Health, followed more than 200,000 adults, without major chronic diseases at the start of the study, for 34 years.

Study participants completed dietary questionnaires every four years across the study period. Their diets were scored based on the intake of 15 food groups – including whole grains, vegetables, poultry, and nuts – to determine their adherence to the PHD. 

The study revealed that participants in the top 10 per cent for adherence to the PHD had a 30 per cent lower risk of premature death, compared to those in the bottom 10 per cent.

And greater adherence to this dietary pattern lowered the risk of death from major diseases, including cancer and heart disease.   

Did you know? The Planetary Health Diet sets the scientific target for nuts as 50g/day (with a range of 0-70g), consisting of 25g each of peanuts and tree nuts.

Among the findings, those in the highest quintile (the top fifth) of adherence to the diet had:

• 14% lower risk of cardiovascular mortality
• 10% lower risk of cancer mortality
• 47% lower risk of respiratory disease mortality, compared with the lowest.

In addition, the researchers found eating in line with the PHD was linked with substantially lower environmental impacts.

For instance, the highest adherence to the PHD was associated with a halving of cropland use (51% lower), and a 29% reduction in greenhouse gases emissions

According to the researchers, the findings show just how linked human and planetary health are.

The study was published in The American Journal of Clinical Nutrition.