The typical dietary intake of L-arginine is 3.5 to 5 grams daily.

L-arginine, even when it is not an essential amino acid as defined above, is a vital one.

Most dietary L-arginine comes from plant and animal proteins.

Sexual Function and Cardiovascular Health: Increasing systemic levels of L-arginine has been demonstrated to significantly improve endothelial function in individuals with essential hypertension, compromised flow-mediated dilation, arterial stiffness, chronic heart failure, impaired glucose tolerance (MetS) and type 2 diabetes – all of which are common concomitant medical conditions associated with Erectile Dysfunction (ED). Supplementing ED patients with L-citrulline can provide systemic as well as sexual performance benefits.

In addition to participating in protein synthesis, it plays a number of other roles in the body.

Effect of L-arginine on immune function: a meta-analysis.

In addition, L-arginine is a precursor in the formation of nitric oxide, creatine, polyamines, L-glutamate, L-proline, agmatin (a possible neurotransmitter in the brain) and the arginine-containing tetrapeptide tuftsin, believed to be an immunomodulator.

The terms L-arginine and arginine are frequently used interchangeably.

General Background While the amino acid is not involved directly in protein synthesis, it is an important intermediate in many metabolic pathways, such as the and the biosynthesis of several compounds, including arginine (see and ), proline (see and ), and putrescine (), which leads to the biosynthesis of other polyamines and pyrimidines.

L-ornithine may be used as an alternative since it metabolizes to L-arginine in the body.


Ornithine is similar in structure to Arginine.

Supplementation with L-arginine increased plasma concentrations of arginine, ornithine, proline, homoarginine, urea, and nitric oxide metabolites without affecting those for lysine, histidine, or methylarginines, while reducing plasma concentrations of ammonia, glutamine, free fatty acids, and triglycerides.

Safety of long-term dietary supplementation with L-arginine in rats.

Beginning at 6 weeks of age, male and female rats were fed a casein-based semi-purified diet containing 0.61 % L-arginine and received drinking water containing L-arginine-HCl.

L-Arginine supplementation reduced plasma levels of leptin.

There is research evidence suggesting that consuming extra ornithine can help promote physical strength and endurance during periods of intense muscle exercise when creatine is needed along with ATP.

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This is a semi-essential amino acid, because although it is normally synthesized in sufficient amounts by the body, supplementation is sometimes required (for example, due to inborn errors of urea synthesis, protein malnutrition, excessive lysine intake, burns, peritoneal dialysis, and rapid growth).

Synthesis of L-ornithine L-aspartate from L-arginine

The liver turns ammonia into urea which is dissolved in water to form urine. Our kidneys are the organ where this occurs and L-ornithine is at the heart of this process.

Synthesis of L-[5-11C]ornithine - ResearchGate

L-ornithine is critical in the process for removing biological waste material. There is some evidence suggesting this particular amino acid helps raise energy levels along with other health benefits.