There was important news from the Harvard T.H. Chan School of Public Health. A new study led by researchers at the school showed that a higher ratio of plant-based protein to animal-based protein in daily diet is expected to reduce the risks of cardiovascular disease (CVD) and coronary heart disease (CHD).
The researchers pointed out that the key driving force for this risk reduction is most likely the replacement of red and processed meats with plant-based proteins. Moreover, they also observed that increasing the proportion of plant-based protein intake while increasing overall protein intake can bring the greatest benefits to heart health.
Currently, although global dietary guidelines advocate increasing the intake of plant-based proteins, the ideal ratio of plant-based protein to animal-based protein has remained unclear. This study is pioneering as it is the first to conduct in-depth research on this ratio and its impact on health, especially heart health.
“The average American has a plant-based protein to animal-based protein ratio of 1:3 in their daily diet. However, our research findings suggest that a ratio of at least 1:2 would be more effective in preventing cardiovascular disease. For the prevention of coronary heart disease, the proportion of plant-based protein should be 1:1.3 or higher,” said Andrea Glenn, the lead author of the study and a visiting scientist in the Department of Nutrition at the Harvard T.H. Chan School of Public Health. Glenn participated in this study as a postdoctoral fellow and is now an assistant professor in the Department of Nutrition and Food Studies at New York University.
The results of this study will be published in the American Journal of Clinical Nutrition on December 2.
The researchers analyzed the data on diet, lifestyle, and heart health of nearly 203,000 men and women over a period of 30 years. These participants were from the Nurses’ Health Studies I and II and the Health Professionals’ Follow-up Study. They reported their dietary intake every four years. Based on this, the researchers calculated each participant’s total daily protein intake (in grams), as well as their specific intakes of animal-based and plant-based proteins. During the entire study period, a total of 16,118 cases of cardiovascular disease were recorded, including more than 10,000 cases of coronary heart disease and more than 6,000 cases of stroke.
After adjusting for participants’ health history, sociodemographic factors, and lifestyle factors, the study found that a higher ratio of plant-based protein to animal-based protein was associated with lower risks of cardiovascular disease and coronary heart disease. Compared with participants with the lowest ratio of plant-based protein to animal-based protein (about 1:4.2), those with the highest ratio (about 1:1.3) had a 19% lower risk of cardiovascular disease and a 27% lower risk of coronary heart disease. The risk reduction was even more significant among participants with higher overall protein intake.
Participants with the highest protein intake (21% of energy coming from protein) and a higher ratio of plant-based protein to animal-based protein had a 28% lower risk of cardiovascular disease and a 36% lower risk of coronary heart disease compared with those with the lowest protein intake (16% of energy). However, no significant association was found between the ratio and the risk of stroke. But the study showed that replacing red and processed meats in the diet with various plant-based sources, such as nuts, could reduce the risk of stroke.
The researchers also explored the question of whether there is a “saturation point” for plant-based protein intake. Once exceeded, it might not only stop bringing additional benefits but might even have negative impacts. The results showed that the risk reduction for cardiovascular disease tended to level off when the ratio of plant-based protein to animal-based protein reached around 1:2, but the risk of coronary heart disease continued to decrease as the proportion of plant-based protein increased.
The researchers said that the above risk reduction is likely due to the replacement of red and processed meats with multiple plant-based protein sources, especially nuts and legumes. Previous studies have confirmed that such replacements can improve cardiometabolic risk factors, including blood lipids, blood pressure, and inflammatory biomarkers. This is partly because plant-based proteins are usually accompanied by large amounts of dietary fiber, antioxidant vitamins, minerals, and healthy fats.
“Most of us need to start adjusting our diet towards plant-based proteins. Specifically, we should reduce the intake of meat, especially red and processed meats, and increase the consumption of legumes and nuts. Such a dietary pattern is beneficial not only for human health but also for the ecological health of the planet,” emphasized Frank Hu, the senior author of the study, the Fredrick J. Stare Professor of Nutrition and Epidemiology at the Harvard T.H. Chan School of Public Health.
The researchers also pointed out that the ratios they identified are only preliminary estimates. Further studies are needed to accurately determine the optimal balance between plant-based and animal-based proteins. In addition, how protein intake affects the risk of stroke also requires further in-depth research.
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