Research from Harvard T.H. Chan School of Public Health highlights benefits of shifting to more plant-based protein sources

A new study from the Harvard T.H. Chan School of Public Health has suggested that consuming a higher ratio of plant-based protein relative to animal-based protein may significantly reduce the risk of cardiovascular disease (CVD) and coronary heart disease (CHD). The findings emphasize the benefits of replacing red and processed meats with plant proteins such as nuts and legumes to improve heart health.

Published on 2 December 2024, in the American Journal of Clinical Nutrition, this study is the first to specifically investigate the ideal ratio of plant to animal protein for heart health. According to lead author Andrea Glenn, now an assistant professor at NYU Steinhardt’s Department of Nutrition and Food Studies, the average American diet currently has a plant-to-animal protein ratio of 1:3, while the study suggests that a ratio of at least 1:2 is more effective for preventing CVD. For CHD prevention, a ratio of 1:1.3 or higher is recommended.

The study analyzed 30 years of data from nearly 203,000 men and women enrolled in the Nurses’ Health Studies I and II and the Health Professionals’ Follow-up Study. Participants reported their dietary intake every four years, and researchers assessed total protein intake, as well as specific intakes of plant and animal proteins. During the study period, 16,118 cases of cardiovascular disease were documented, including over 10,000 cases of coronary heart disease and more than 6,000 stroke cases.

After adjusting for factors such as health history, demographics, and lifestyle choices, the researchers found that participants who consumed the highest plant-to-animal protein ratio (approximately 1:1.3) had a 19% lower risk of CVD and a 27% lower risk of CHD compared to those with the lowest ratio (approximately 1:4.2).

The heart health benefits were even greater for participants with higher overall protein intake. Those who consumed 21% of their daily energy from protein, while maintaining a higher plant-to-animal protein ratio, experienced a 28% lower risk of CVD and a 36% lower risk of CHD compared to participants who consumed only 16% of their energy from protein.

While the study did not find a significant association between the plant-to-animal protein ratio and stroke risk, replacing red and processed meats with plant protein sources such as nuts was linked to a reduced risk of stroke. The researchers noted that these heart health benefits are likely due to plant proteins being rich in fiber, antioxidants, vitamins, minerals, and healthy fats, which can improve blood lipids, blood pressure, and inflammation markers.

The study found that while CVD risk reductions plateaued around a 1:2 plant-to-animal protein ratio, CHD risk continued to decrease with higher ratios of plant protein. This suggests that further increasing plant protein intake may offer additional benefits for coronary heart disease prevention.

Senior author Frank Hu, Fredrick J. Stare Professor of Nutrition and Epidemiology at Harvard Chan School, emphasized the broader implications of these findings. “Most of us need to begin shifting our diets toward plant-based proteins. We can do so by cutting down on meat, especially red and processed meats, and eating more legumes and nuts. Such a dietary pattern is beneficial not just for human health but also the health of our planet.”

The researchers acknowledge that the identified ratios are estimates and that further studies are needed to determine the optimal balance between plant and animal protein. Additional research is also required to understand how different protein sources influence stroke risk.

This study provides important evidence supporting global dietary guidelines that advocate for higher intake of plant-based proteins. By making conscious dietary changes, such as replacing red and processed meats with plant-based alternatives, individuals can significantly reduce their risk of heart disease while promoting sustainable food practices.