High-protein diets may help people lose weight and build muscle.
But in a new study from the Washington University in St. Louis, researchers found a downside: more plaque in the arteries.
They found that high-protein diets spur unstable plaque—the kind most prone to rupturing and causing blocked arteries. More plaque buildup in the arteries, particularly if it’s unstable, increases the risk of a heart attack.
In the study, the researchers studied mice fed a high-fat diet to deliberately induce atherosclerosis, or plaque buildup in the arteries.
Some of the mice received a high-fat diet that was also high in protein. And others were fed a high-fat, low-protein diet for comparison.
The team found the mice on the high-fat, high-protein diet developed worse atherosclerosis—about 30% more plaque in the arteries—than mice on the high-fat, normal-protein diet, despite the fact that the mice eating more protein did not gain weight, unlike the mice on the high-fat, normal-protein diet.
This study is not the first to show a telltale increase in plaque with high-protein diets, but it offers a deeper understanding of the impact of high protein with a detailed analysis of the plaques.
The study shows how and why dietary protein leads to the development of unstable plaques.
Plaque contains a mix of fat, cholesterol, calcium deposits, and dead cells. Past work has shown that immune cells called macrophages work to clean up plaque in arteries.
But the environment inside plaque can overwhelm these cells, and when such cells die, they make the problem worse, contributing to plaque buildup and increasing plaque complexity.
To understand how high dietary protein might increase plaque complexity, the team studied the path protein takes after it has been digested—broken down into its original building blocks, called amino acids.
They found that excess amino acids from a high-protein diet activate a protein in macrophages, which tells the cell to grow rather than go about its housecleaning tasks.
The signals shut down the cells’ ability to clean up the toxic waste of the plaque, and this sets off a chain of events that results in macrophage death.
The researchers found that certain amino acids, especially leucine and arginine, were more potent in leading to cell death—than other amino acids.
Leucine is particularly high in red meat, compared with fish or plant sources of protein.
If you care about heart health, please read studies about this common antibiotic drug linked to higher heart attack risk and findings of these two food linked to higher risk of diabetes, stroke and heart disease.
For more information about heart disease, please see recent studies about this bone problem strongly linked to heart disease in women and results showing that this common health issue in middle-age may predict heart failure later in life.
The study is published in Nature Metabolism. One author of the study is Babak Razani.
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