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Study shows healthy diet crucial for planetary health

The strong connection between individual and Planetary Health, has been highlighted in a recent study published by the Harvard T.H. Chan School of Public Health. 

The study stresses the critical role of dietary choices in amplifying environmental sustainability and public wellbeing. 

According to the study which was published in The American Journal of Clinical Nutrition last month, ‘People who eat a healthy, sustainable diet may substantially lower their risk of premature death in addition to their environmental impact'.

Corresponding author Walter Willett, professor of epidemiology and nutrition said the findings showed just how linked human and planetary health were. ‘Eating healthfully boosts environmental sustainability—which in turn is essential for the health and wellbeing of every person on earth.’

'Climate change has our planet on track for ecological disaster, and our food system plays a major role. Shifting how we eat can help slow the process of climate change. And what’s healthiest for the planet is also healthiest for humans.’

While other studies have found that diets emphasising plant-based foods over animal-sourced foods could have  benefits for human and planetary health, most have used one-time dietary assessments, which produce weaker results than looking at diets over a long period of time.

This is the first large study to directly evaluate the impacts of adherence to recommendations in the landmark 2019 EAT-Lancet report.

The researchers named the dietary pattern outlined in the report—which emphasizes a variety of minimally processed plant foods but allows for modest consumption of meat and dairy foods—the Planetary Health Diet (PHD). 

They used health data from more than 200,000 women and men enrolled in the Nurses’ Health Study I and II and the Health Professionals Follow-Up Study. Participants were free of major chronic diseases at the start of the study and completed dietary questionnaires every four years for up to 34 years. Participants’ diets were scored based on intake of 15 food groups—including whole grains, vegetables, poultry, and nuts—to quantify adherence to the PHD.

The study found that the risk of premature death was 30% lower in the top 10% of participants most closely adhering to PHD compared to those in the lowest 10%. Every major cause of death, including cancerheart disease, and lung disease, was lower with greater adherence to this dietary pattern.

In addition, the researchers found that those with the highest adherence to the PHD had a substantially lower environmental impact than those with the lowest adherence, including 29% lower greenhouse gas emissions, 21% lower fertilizer needs, and 51% lower cropland use.

The researchers noted that land use reduction is particularly important as a facilitator of re-forestation, which is seen as an effective way to further reduce levels of greenhouse gases that are driving climate change.