Researchers found that postmenopausal women who follow a high-protein diet had a significantly higher rate of heart failure than those who ate less protein daily or ate more vegetable protein.
The study examined the dietary protein intake of 103,878 women, ages 50 to 79, from 1993 to 1998. They self-reported their daily diets, which researchers noted can be unreliable; researchers also used biomarker data to determine actual amounts of dietary protein. Although all participants were free of heart failure during that period, about 1,700 of them developed heart failure by 2005.
Researchers adjusted for age, education, race or ethnicity and heart failure risk factors such as high blood pressure, diabetes, coronary artery disease, anemia or atrial fibrillation.
"We found that by increasing the total dietary protein intake, there was a statically significant increase in the incidence of heart failure," said Dr. Mohamad Barbour, an internist at the Alpert Medical School of Brown University, Memorial Hospital of Rhode Island and lead author of the study.
In fact, the risk was almost double.
Meanwhile, women whose proteins were sourced mainly from vegetables appeared to be at a lower risk of heart failure.
This could be attributed to the molecular mechanisms of animal protein, Barbour said, explaining that animal proteins can turn to toxic molecules, which can in turn affect the function of the heart's left ventricle and lead to heart failure. They can also increase the body mass index, a known risk factor for heart failure.
"Our study should be interpreted with caution," warned Barbour. "It appears that a high-protein diet may increase the risk of heart failure among postmenopausal women; however, more research will be needed."
Dr. Mingyang Song, a researcher at Massachusetts General Hospital and the Harvard T.H. Chan School of Public Health, described the findings as interesting. Song was the lead author of research published this year that found replacing animal protein with plant protein in a person's diet
was associated with a decreased risk of death. He was not involved in the new research.
"People who eat high vegetable proteins may also have a healthier lifestyle," Song said. This may imply that other factors are responsible for lowering the risk of heart failure for that group, he added.
"I think it'll be good to replicate the results in other studies," he said, suggesting that a more controlled group with a more controlled food intake could be required for that purpose.