While not exactly an essential amino acid, meaning one the body cannot make on its own and therefore must get from outside sources. L-arginine is considered somewhat essential because it’s highly important for many functions yet usually present in low quantities, especially as someone get older. One of the biggest benefits of L-arginine is its ability to improve blood flow and circulation. In the body, L-arginine is converted into nitric oxide, which causes blood vessels to open wider. This has multiple benefits, including improving immune function, fertility, detoxification and brain power. L-arginine stimulates production of certain hormones to generate more growth and energy output. Which is why it was believed to enhance physical performance, stamina and strength.