A high-protein diet can lead to weight loss, but it may also boost heart attack and stroke risk, a new study has found.

Investigators fed mice a high-fat, high-protein diet. While the animals did not gain weight, they developed about 30% more arterial plaque than mice fed a high-fat, normal protein diet, reported Babak Razani, M.D., Ph.D., from Washington University, St. Louis.

In addition, certain amino acids in protein, such as leucine and arginine, helped derail the process that normally helps prevent plaque buildup, Razani and colleagues found. This led to cell death, making the plaques more unstable and further raising heart attack and stroke risk, they said.

Based on these findings, Razani foresees future studies of these amino acids and their role in cardiovascular risk. “Leucine is particularly high in red meat, compared with, say, fish or plant sources of protein,” he added. 

Full findings appear in Nature Metabolism.