This simple plant-based diet could slash heart disease risk by 28 percent, 20-year study finds

The findings showed that women whose diet most closely followed the Planetary Health Diet had about a 28% lower risk of cardiovascular disease compared with women in the group scoring the lowest for adherence. However, even moderate adherence to the diet was linked with lower risk.

The Planetary Health Diet emphasizes foods such as fruits, vegetables, whole grains, legumes, nuts and unsaturated fats while limiting foods such as red and processed meats, added sugars, refined grains and saturated fats.

“Our results suggest that people may not need to follow a perfect or very restrictive diet to see potential heart-health benefits,” said Donya Shahamati, a doctoral student in public health at the University of California, Irvine. “This is especially important for postmenopausal women, because cardiovascular risk increases with age and tends to rise after menopause.”

Shahamati will present the findings at NUTRITION 2026, the flagship annual meeting of the American Society for Nutrition, held July 25–28 in National Harbor, Maryland, just outside Washington, D.C.

“Moving toward a more plant-forward, higher-quality diet can be accomplished through small, realistic changes,” said Shahamati. “These changes might include filling half the plate with vegetables more often; using avocado or olive oil in place of butter; choosing oatmeal or whole-grain cereal for breakfast; or trying a meatless meal once per week.”

For the new research, the investigators followed 66,892 participants in the Women’s Health Initiative (WHI), a long-term national health study funded by the National Heart, Lung and Blood Institute at the National Institutes of Health. All the women included in the analysis were free of cardiovascular disease at the start of the study (1994-1998) and had complete information on diet and other important health and lifestyle factors.

Using information collected through a food frequency questionnaire administered at the beginning of the study, the researchers calculated a Planetary Health Diet Index score for each study participant, with higher scores indicating a diet was more aligned with the Planetary Health Diet. The researchers then divided the women into five groups based on how closely their diets aligned with the Planetary Health Diet.

The women, who were around 63 years old at the start of the study, were followed for about 20 years to see who developed cardiovascular disease. When analyzing the data, the researchers adjusted for several factors that could affect cardiovascular risk, including age, race and ethnicity, education, income, smoking, alcohol intake, physical activity, body mass index and total calorie intake.

“We did not only look at overall cardiovascular disease,” said Shahamati. “We also looked separately at coronary heart disease, stroke and heart failure. This helped us see whether the pattern was similar across different types of cardiovascular outcomes.”

Overall, the results showed that women in the group whose diets were more closely aligned with the Planetary Health Diet had the lowest risk of cardiovascular disease. These women also showed a decreased risk of heart disease, heart failure and stroke risk compared to the women in the lowest-adherence group.

However, even moderate adherence to the diet was associated with a decrease in risk, with each 10-point increase in Planetary Health Diet Index score linked to further risk reduction.

The researchers caution that an observational study like this cannot show that diet directly caused the lower risk in women.

The research team is now exploring other aspects of diet and health in older adult populations. For example, they are examining how diet quality changes over time in this population, information that could help support healthy aging and prevent chronic diseases.