A plant-based eating regimen designed to save the Earth also saves people's lives, a large study confirms.

"Shifting how we eat can help slow the process of climate change," said corresponding author Dr. Walter Willett, a professor of epidemiology and nutrition at Harvard T.H. Chan School of Public Health. "And what's healthiest for the planet is also healthiest for humans."

Known as the Planetary Health Diet (PHD), the regimen emphasizes minimally processed plant foods, while modest intake of meat and dairy foods are allowed.

While other studies have shown that plant-based diets have benefits for the planet and people alike, most have looked at one point in time. The new study drew on health data from more than 200,000 men and women who were followed for up to 34 years.

Researchers found those whose diets most closely hewed to the PHD regimen had a 30% lower risk of early death compared to those whose diets were the least like it. 

That was true for every major cause of death -- cancer, heart disease and lung disease, the study found. None of the participants had major chronic illnesses at the outset. 

They completed dietary questionnaires every four years and were scored based on intake of 15 food groups, including veggies, poultry, whole grains and nuts. 

Those whose eating habits were closest to the PHD had a bigger positive impact on the environment as well, the study showed. Compared to those with the lowest adherence, their impact included 29% lower greenhouse gas emissions; 21% lower fertilizer needs; and 51% lower cropland use.

The findings were published online June 10 in The American Journal of Clinical Nutrition. Research grants from the National Institutes of Health supported the study.

Using less land for food production is a key to promoting re-forestation, researchers said. Re-forestation is key to reducing greenhouse gas levels that fuel climate change.

"The findings show just how linked human and planetary health are," Willett said in a Harvard news release. "Eating healthfully boosts environmental sustainability -- which in turn is essential for the health and well-being of every person on earth."