L-Arginine is one of 20 amino acids the building blocks of protein. L-Arginine can serve as an energy precursor and is one of the most important amino acids involved in supporting heart health. High-dose L-arginine may help to maintain bp levels. In the body, the amino acid arginine changes into nitric oxide (NO). Some evidence shows that arginine may help improve blood flow in the arteries of the heart. That may improve symptoms of clogged arteries, chest pain or angina, and coronary artery disease.