L-arginine is a semi-essential amino acid involved in numerous areas of human biochemistry, including ammonia detoxification, hormone secretion, and immune modulation. Arginine is also well known as a precursor to nitric oxide (NO), a key component of endothelial-derived relaxing factor, an endogenous messenger molecule involved in a variety of endothelium-dependent physiological effects in the cardiovascular system.

L-ornithine is a metabolite of arginine in the body, formed as a byproduct of the action of the arginase enzyme on arginine. L-arginine is required for the body to synthesize nitric oxide, which enables the arterial system to retain its youthful elasticity. Nitric oxide also helps to produce an endothelial-derived relaxing factor, which is needed by the arterial system to expand and contract with each heartbeat.

L-arginine may also help maintain the health of the immune system.

L-arginine is a key building block to maintaining healthy tissue and bone. L-ornithine may also be used for this purpose.

Some studies suggest that either independently or combined, arginine and ornithine appear to stimulate growth hormone (GH) based on the increase in strength and muscle mass that was produced while intensely working out.Other research evidences ornithine’s ability to stimulate GH release.Another study showed a combination of ornithine with acetyl-L-carnitine enhanced the GH release feedback loop. However, studies suggest that low doses of L-arginine and/or L-ornithine are unlikely to effect GH release. A minimum dose of L-arginine to promote GH release is probably 5 to 9 grams.