Greater planetary health diet adherence tied to better mortality, environmental outcomes

Key takeaways:

• Higher adherence to the planetary health diet was tied to decreased mortality from causes like cancer and CVD.
• Greater adherence also decreased greenhouse gas emissions and cropland use.

Greater adherence to the planetary health diet was associated with a lower risk for an early death from several causes and produced a significantly lower environmental impact, a study showed.

Walter C. Willett, MD, DrPh, a professor of epidemiology and nutrition at Harvard’s T.H. Chan School of Public Health, co-chaired the EAT-Lancet Commission which aimed to identify an eating pattern that was “both healthy and environmentally sustainable”

The diet, often referred to as the planetary health diet, “is a flexible way of eating that can include modest amounts of dairy foods or meat and could include vegan or vegetarian versions,” he told Healio.

Specifically, the diet emphasizes high-quality plant-based foods and lower amounts of animal-based foods, added sugars, unhealthy fats and refined grains, according to Havard.

Previous research on the planetary health diet suggested that 11 million deaths a year could be prevented if the dietary pattern’s targets were met.

In the prospective cohort study, Willett and colleagues assessed over 20 years’ worth of dietary data from:

• 66,692 from the Nurses’ Health Study;
• 92,438 women from the Nurses’ Health Study II; and
• 47,274 men from the Health Professionals Follow-up Study.

All participants were free of cancer, CVD and diabetes at baseline.

The researchers use Planetary Health Diet Index (PHDI) scores based on the intake of 15 food groups to determine environmental and various mortality outcomes associated with higher or lower adherence to the planetary health diet.

Overall, compared with those in the lowest quintile of PHDI adherence, those in the highest quintile had a:

• 23% lower risk for all-cause mortality (HR = 0.77; 95% CI, 0.75-0.8);
• 14% lower risk for cardiovascular mortality (HR = 0.86; 95% CI, 0.81-0.91);
• 10% lower risk for cancer mortality (HR = 0.9; 95% CI, 0.85-0.95);
• 47% lower risk for respiratory mortality (HR = 0.53; 95% CI: 0.48-0.59); and
• 28% lower risk for neurodegenerative mortality (HR = 0.72; 95% CI, 0.67-0.78).

In women, a higher adherence to the PHDI was also significantly associated with a lower risk of death from infectious diseases (HR = 0.62; 95% CI, 0.51-0.76).

Associations remained even after Willett and colleagues adjusted for lifestyle factors, high BP and elevated cholesterol.

Greater diet adherence was also associated with lower environmental impact. For example, vs. the lowest quintile of PHDI, the highest quintile had:

• 29% lower greenhouse gas emissions;
• 51% lower cropland use; and
• 13% lower irrigation water needs.

The data, published in the American Journal of Clinical Nutrition, “fill an important gap because the U.S. Dietary Guidelines are completely silent about the environmental impacts of dietary choices,” Willett said.

He explained that dietary choices have a significant impact on wellbeing and health outcomes, “and we need to emphasize this more in counseling patients.”

“Many people are also concerned about the health of our planet because we are currently not on a path that will lead to a good future for our children and grandchildren,” he said. “This analysis provides strong evidence that consuming a planetary health dietary pattern can provide a double win: better health for both individuals and our planet.”

The researchers noted that changes in diet due to chronic disease development may have led to an over- or underestimation of mortality based on PHDI adherence, and the generalizability of the study may be limited because the cohort consisted mostly of non-Hispanic white health professionals.

“Further research on the most effective ways to integrate nutrition into clinical practice is needed, recognizing that primary care providers are already stressed,” Willett said. “We specifically need more research on how knowledge about the environmental effects of food will influence the food choices of patients.”

For more information:

Maya Brownstein can be reached at mbrownstein@hsph.harvard.edu.

References:

• Bui L, et al. Am J Clin Nutr. 2024;doi:10.1016/j.ajcnut.2024.03.019.
• Planetary Health Diet associated with lower risk of premature death, lower environmental impact. https://www.hsph.harvard.edu/news/press-releases/planetary-health-diet-associated-with-lower-risk-of-premature-death-lower-environmental-impact/. Published June 10, 2024. Accessed June 13, 2024.
• Plate and the planet. https://www.hsph.harvard.edu/nutritionsource/sustainability/plate-and-planet/. Accessed June 13, 2024.