Arginine, or L-arginine, is an amino acid that is made in the body. As a supplement, it seems to help with several conditions, from migraines to inflammation. Heart Benefits? In the body, the amino acid arginine changes into nitric oxide (NO). Nitric oxide is a powerful neurotransmitter that helps blood vessels relax and also improves circulation. Some evidence shows that arginine may help improve blood flow in the arteries of the heart.