Low Nitric Oxide Levels L-arginine, however, another staple ingredient on most (2)penile enlargement pills, can be a precursor of nitric oxide supplements, which is known as the erection compound. Nitric oxide is important to widen the veins inside your penis, allowing more blood to penetrate to chamber of spongy erectile tissues. Studies show that L-arginine might help improve cardiovascular health. As you may know, a proper heart means better erections.