People who eat a healthy, sustainable diet may substantially lower their risk of premature death in addition to their environmental impact, according to a new study led by Harvard T.H. Chan School of Public Health.
Arguably, the first large study to directly evaluate the impacts of adherence to recommendations in the landmark 2019 EAT-Lancet report, researchers participating in the program have 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). The study was published online in The American Journal of Clinical Nutrition.
While other studies have found that diets emphasizing 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.
“Climate change has our planet on track for ecological disaster, and our food system plays a major role,” said corresponding author Walter Willett, professor of epidemiology and nutrition. “Shifting how we eat can help slow the process of climate change. And what’s healthiest for the planet is also healthiest for humans.”
The researchers 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.
Risk of premature death was 30 per cent lower in the top 10 per cent of participants most closely adhering to PHD compared to those in the lowest 10 per cent. Every major cause of death, including cancer, heart disease, and lung disease, was lower with greater adherence to this dietary pattern.
The study found that the risk of premature death was 30 per cent lower in the top 10 per cent of participants most closely adhering to PHD compared to those in the lowest 10 per cent. Every major cause of death, including cancer, heart 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 per cent lower greenhouse gas emissions, 21 per cent lower fertilizer needs, and 51 per cent 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.
“The findings show just how linked human and planetary health are. Eating healthfully boosts environmental sustainability—which in turn is essential for the health and wellbeing of every person on earth.”
Walter Willett, professor of epidemiology and nutrition< Harvard School of Public Health
“Our study is noteworthy given that the U.S. Department of Agriculture has refused to consider the environmental impacts of dietary choices, and any reference to the environmental effects of diet will not be allowed in the upcoming revision of the U.S. Dietary Guidelines,” said Willett. “The findings show just how linked human and planetary health are. Eating healthfully boosts environmental sustainability—which in turn is essential for the health and wellbeing of every person on earth.”
What is Planetary Health Diet?
Planetary health diet constitutes an optimal diet for human health and environmental sustainability. It emphasizes a plant-forward diet where whole grains, fruits, vegetables, nuts and legumes comprise a greater proportion of foods consumed. Meat and dairy constitute important parts of the diet but in significantly smaller proportions than whole grains, fruits, vegetables, nuts and legumes, according to a LANCET study.
In addition to the targets set within each section, the dietary targets also suggest that the average adult requires 2500 kcal per day. While this amount will vary based on age, gender, activity levels and health profiles, overconsumption is a waste of food with both health and environmental costs.