Probably you have heard this before and it has been confirmed that eating red meat may be linked to a higher risk of death.
However, replacing animal protein in your diet with plant protein is associated with a decreased risk of death, according to the research, which was published in JAMA Internal Medicine on Monday.
Scientists have long connected processed red meats with a wide spectrum of chronic diseases, such as cancer, diabetes and heart disease.
Now, the new paper reveals that these associations may still exist when examining protein intake overall, said Dr. Mingyang Song, a researcher at Massachusetts General Hospital and the Harvard T.H. Chan School of Public Health, who served as lead author of the paper.
"While it is important to know how much protein people should consume to achieve the optimal health benefit, from a broad dietary perspective, what foods people choose to consume to get protein is equally important," Song said.
"Our findings have important public health implications," he added. "They can help refine the current dietary recommendations about protein intake and really get to the point that it is not only the amount but also the food sources of protein that are critical for long-term health."
The researchers found that associations between protein intake and risk of death were confined to participants who had at least one unhealthy lifestyle habit or ailment, such as smoking, heavy drinking, obesity or physical inactivity.
Specifically, a 10% increase in animal protein intake was linked to a 2% increase in overall mortality and 8% increase in risk of cardiovascular-related death, Song said. However, a 3% increase in plant protein intake was linked to a 10% decrease in overall mortality and a 12% decrease in cardiovascular mortality.
Why animal protein is linked to mortality and plant protein is linked to a lower risk of death remains largely a mystery, Song said.
"But high animal protein intake has been linked to higher levels of insulin-like growth factor 1, a protein that has been linked to worse health outcomes, whereas high plant protein intake has been associated with lower blood pressure ... and improved insulin sensitivity," Song said.
"Alternatively, it is possible that other components in the foods than protein per se may be the culprit," he added. "For example, processed red meat is high in sodium, nitrites and nitrates, which have all been linked to worse health outcomes."
The U.S. government's 2015-20 dietary guideline recommend a diet with limited saturated fat, less sodium and more vegetables and whole grains.