In a new study, researchers found that high-protein diets may help people lose weight and build muscle, but they have a downside: They lead to more plaque in the arteries.
Further, 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.
The research was conducted by a team at Washington University School of Medicine in St. Louis.
There are clear weight-loss benefits to high-protein diets, which has boosted their popularity in recent years.
But some studies have linked high dietary protein to cardiovascular problems.
In the study, the team decided to take a look at whether there is truly a causal link between high dietary protein and poorer heart health.
The researchers studied mice with 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.
The team says 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 the detailed analysis of the plaques.
In other words, 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.
The team also 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.
Certain amino acids, especially leucine and arginine, were more dangerous — and derailing macrophages from their cleanup duties, leading to cell death — than other amino acids.
The team says leucine is particularly high in red meat, compared with, say, fish or plant sources of protein.
A future study might look at high-protein diets with different amino acid contents to see if that could have an effect on plaque complexity.
One author of the study is Babak Razani, MD, Ph.D., an associate professor of medicine.
The study is published in the journal Nature Metabolism.
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