A new study finds that the more people who followed an environmentally sustainable diet that emphasized nutrients from plants, the lower their risk of death from cancer, heart disease, Alzheimer's disease and a variety of other causes.
(J.M. Hirsch / Associated Press)
Every time you scoop up a spoonful of overnight oats or sink your teeth into a cheeseburger, you're eating for two — for the sake of your own health and that of the planet.
Researchers estimate that approx 30% of greenhouse gas emissions, 40% of land use And 70% of freshwater use is linked to food production. The pressure will only increase as the Earth's population grows 10 billion marks by 2050.
Will it be possible to provide all those people with a nutritious diet in a way that is environmentally sustainable?
That question prompted an international group of scientists to “Planetary Health Diet” that's heavy on plants – including vegetables, fruits, whole grains, nuts, legumes and unsaturated oils from sources such as olives and canola – along with modest amounts of dairy, poultry, fish and other foods derived from animals. It also provides a little bit of red meat, refined grains and sugar. (You can even eat a burger about once a week.)
If the entire world were to embrace such a diet – along with adopting better agricultural practices and reducing food waste – greenhouse gas emissions would be roughly halved, the scientists calculated when they introduced their eating plan in 2019. They also predicted that the number of premature deaths around the world would drop by as much as 24%.
“That amounts to about 11 million deaths per year,” which would not happen, he said Dr. Walter Willetta co-chair of the group known as the EAT-Lancet Committee.
Now Willett and his colleagues at Harvard University have compared their work with real-world data.
The Harvard team has created a Planetary Health Diet Index, which quantifies the extent to which a person's diet meets the committee's goals. There are 15 food groups and people were scored on a 5 or 10 point scale for each group. The maximum possible score was 140, which would indicate perfect alignment with the ideal eating plan.
The researchers assigned PDHI scores to more than 200,000 people who participated in the study Health Study of Nursesthe Nurses' Health Study II and the Follow-up study for health professionals. All participants provided detailed information about their diets when they took part in the studies in the 1970s and 1980s, and for more than two decades they updated that information at least once every four years.
The women in the two Nurses' Health Studies improved their diet over time: the average index score for participants in NHS1 rose from 75.7 in 1986 to 84.5 in 2010, while the average for women in NHS2 rose from 70 .4 in 1990 to 85.9 in 2015. However, the average score for men in HPFS remained stable at around 78.
By the time the tracking periods ended in 2019, 54,536 people in the three studies had died.
The researchers hypothesized that the higher a person's PDHI score, the lower the risk of being among the deceased. And after taking into account demographic factors like age, race and neighborhood income, as well as health conditions like a family history of cardiovascular disease or cancer, that's exactly what they found.
“We saw a very strong, very clear inverse relationship,” said Willett, professor of epidemiology and nutrition at the Harvard TH Chan School of Public Health. “Across the board, everything we looked at was lower for people who were most adherent to the planetary health diet.”
Compared to the 20% of people with the lowest index scores, the 20% with the highest scores were 23% less likely to die from any cause during the study period. They were also 14% less likely to die from cardiovascular disease, 10% less likely to die from cancer, 47% less likely to die from a respiratory disease, 28% less likely to die from a neurodegenerative disease such as Alzheimer's disease, and 22% less likely to die from a neurodegenerative disease such as Alzheimer's disease. less likely to die from an infectious disease.
Among men and women, eating more whole grains, fruit, poultry, nuts, soy and unsaturated fats were each associated with a lower risk of death. On the other hand, eating more starchy vegetables such as potatoes, red or processed meat, eggs, saturated fats, added sugar or sugar from fruit juices were each associated with a higher risk of death.
Willett and his collaborators also consulted a database that added up the environmental impacts of different foods to see whether healthier diets were better for the planet. Compared to the diets of people with the lowest PDHI scores, the diets of those with the highest scores required 21% less fertilizer, 51% less arable land and 13% less water and produced 29% fewer greenhouse gas emissions.
Willett said he was “surprised by the strength of some of these findings,” adding that the relationship goes both ways. For example, if fewer hectares are cultivated, there is less particulate matter in the air, and if fewer animals are kept nearby, the risk of antibiotic resistance decreases.
“There are many very important indirect health effects that come from a better environment,” he said.
The results were published Monday in the American Journal of Clinical Nutrition.
This isn't the first study to link planetary health diets to a reduced risk of premature death – researchers have seen the connection in the United Kingdom And in Sweden. But the new work is the first to apply a more precise dietary index to a large sample of Americans and use it to assess their risk of death.
That's an “important” step forward, he said Zach Conrada professor at William & Mary who specializes in nutritional epidemiology and food systems.
However, he said more work is needed to show that planetary health diets are as good for the Earth as they are for Earthlings.
“It remains to be shown that healthy diets are also more environmentally friendly,” says Conrad, who was not involved in the new research. “It is important that we move away from inferring a link between food quality and sustainability and instead move towards measuring it.”
