L-arginine

Efficacy rating:

ÒÒÒ...Positive clinical trials

Safety rating:

●...No safety concerns despite wide use.

What is L-arginine?

Eggs, meats, and milk are all sources of arginine. The physiologically active form, L-arginine, is the natural product obtained by hydrolysis of proteins. Arginine also may be synthesized in the laboratory. Because L-arginine may be synthesized in the body, it is classified as a nonessential amino acid in adults.

What is L-arginine used for?

Overview

Arginine is classified as a nonessential amino acid but may become semiessential in stressful situations, including periods of growth (during childhood or pregnancy) or trauma to the body (eg, liver disease, severe sepsis, wound healing).

L-arginine is involved in the generation of nitric oxide in the body. Nitric oxide is produced by human cells and is involved in many physiological and pathophysiological processes. L-arginine supplementation to raise nitric oxide levels has been suggested to be beneficial in many areas. It has been promoted as a growth stimulant and as a treatment of erectile dysfunction in men.

Cardiovascular and vascular effects

Studies in animals and humans have shown some properties of nitric oxide that may influence cardiovascular health. Nitric oxide has a scavenging effect on superoxide radicals and inhibits platelet aggregation and endothelial permeability. A deficiency in nitric acid has been linked to arterial stiffness. Increased concentrations of L-arginine may improve vascular disease by maintaining nitric oxide levels. Human clinical data evaluating the effect of L-arginine on heart attack and stroke patients are inconclusive to date. Hypertensive pregnant women receiving an infusion of arginine showed a decrease in blood pressure. There may be a role for L-arginine in treating glaucoma and diabetic eye problems, as it reduces arterial pressure and increases retinal blood flow.

Nutritional, metabolic, and immunostimulatory action

Arginine is classified as a nonessential amino acid but may be considered semiessential in stressful situations, including periods of growth (childhood or pregnancy) or trauma to the body (eg, liver disease, sepsis, wound healing). Animal studies show improved healing of wounds, bone, burns, GI tract, and tendons. Immunostimulatory properties were demonstrated in jaundiced laboratory animals.

Other uses

Relaxation of the smooth muscle in the penis requires nitric oxide synthesized by L-arginine, suggesting a role in erectile dysfunction. While laboratory animal studies showed erectile response, human clinical trials failed to produce the same results.

What is the dosage of L-arginine?

L-arginine has been studied at oral doses of 6 to 30 g/day for a variety of conditions. Parenteral administration also has been used.

Is L-arginine safe?

Contraindications

Contraindications have not been identified. L-arginine is not recommended in patients following an acute heart attack.

Pregnancy/nursing

Specific information regarding safety and efficacy during pregnancy and lactation is lacking, although several trials have been conducted in pregnant women without notable adverse reactions.

Interactions

L-arginine has unpredictable effects on insulin and cholesterol-lowering agents. L-arginine may potentiate the effects of isosorbide mononitrate and sodium nitroprusside.

Side Effects

L-arginine has few reported adverse reactions. Nausea and diarrhea have been reported infrequently.

Toxicities

Parenteral administration at high doses has caused metabolic acidosis. High concentrations of nitric oxide are considered toxic to brain tissue.

References