A simple amino acid with incredible potential benefits.

Posted by Mark Hamilton on

All about the power of L Arginine


  • Circulation, including cardiovascular support


  • Athletic performance


  • Metabolic syndrome


  • Fertility


  • Male sexual function


  • Interstitial cystitis


Circulation and Cardiovascular Health

A primary mechanism of L-arginine relates to its role as a substrate for the nitric oxide synthase (NOS) enzyme. Within the vascular endothelial cells, NOS converts L-arginine to nitric oxide, which causes vasodilation of blood vessels and subsequently an improvement in circulation.


Many of the documented

benefits of arginine stem from the action of nitric oxide.

The numerous benefits of L-arginine to cardiovascular health have been widely documented in scientific literature. Both intravenous and oral administration of L-arginine has been shown to induce peripheral vasodilation and improve endothelium-dependent vasodilation. This action is especially relevant in the prevention of conditions such as hypertension and congestive heart failure (CHF) where peripheral blood flow is reduced.  Evidence from several studies suggests that dietary supplementation with L-arginine restores endogenous nitric oxide activity and inhibits platelet aggregation in individuals with hypercholesterolemia.

Athletic Performance

L-arginine is perhaps best known for its ergogenic (performance enhancing) potential and as such, has

become a popular nutritional supplement amongst athletes and active individuals. It is thought that there are several mechanics that account for its ergogenic actions. L-arginine is required for production of various compounds necessary for muscular energy production, including creatine phosphate and phosphoarginine. Although studies show that creatine increases muscular strength and muscle fibre size, it’s assumed these benefits are from creatine supplementation rather than L-arginine, however creatine-induced benefits as a result of supplemental arginine remains a sound physiological theory.

The augmentation of nitric oxide by L-arginine is proposed to facilitate an increase of nutrients to the muscles, resulting in the so-called ‘muscle-pump’ associated with resistance training. Improved circulation is also claimed to aid recovery. These claims however, are generally not supported by the literature.

Benefits for the athlete, beyond those related to vasodilation, are more substantially supported by scientific research. Studies suggest supplemental L-arginine reduces lactic acid, ammonia and blood glucose. Both lactic acid and ammonia accumulate during exercise and lead to fatigue.

Clearing plasma glucose allows for more energy availability to the muscle cells.

A controversial area of research centres on the effects of oral L-arginine supplementation on growth hormone (GH). Athletes and body builders looking to increase muscle mass have utilised L-arginine supplementation, some with intravenously administered L-arginine at relatively high doses (30-40g), yielding results. However, recent findings in this area have shown that resting GH responses also increase with oral ingestion of L-arginine at the dose range of 5–9 g. 

Interestingly, studies show that L-arginine alone increases the resting GH levels at least 100%, while exercise increases GH levels by 300–500%. The combination of oral arginine plus exercise diminishes the GH response, however, and only increases GH levels by around 200% compared to resting levels.

Therefore using arginine on rest days to augment GH release between training bouts would seem an appropriate course of action for athletes.

Metabolic Syndrome

Metabolic syndrome is a cluster of symptoms — hypertension, elevated blood sugar levels, abdominal obesity and hypercholesterolemia — that occur together, which increase the risk of heart disease, stroke and diabetes. Preliminary studies are showing that L-arginine may play a role in the management of metabolic syndrome. The supporting research highlights several pathways by which L-arginine may work.

One early study in this area demonstrated that L-arginine supplementation affects zinc status in obese patients, consequently leading to an improvements in insulin production and sensitivity.

Subsequent studies demonstrate that L-arginine plays an important role in regulating lipid metabolism in animals and humans. Although a number of biochemical and molecular mechanisms have been proposed to explain roles for arginine in metabolism of energy substrates, (such as reducing inflammatory cytokines and fasting glucose levels) further experimental evidence is warranted to support these propositions.



L-arginine has been proposed as an aid to male and female fertility and these claims are supported by scientific literature, although not extensively.

Preliminary research shows that L-arginine supplementation over a period of several months, increases sperm count, quality, and motility. However, when the initial sperm count was very low (such as less than 10 million per ml), little or no benefit was observed. Although initial reports attribute some pregnancies to arginine supplementation, no controlled research has confirmed these claims.

L-arginine may benefit some women undergoing assisted reproduction. For those classed as ‘poor responders’, oral L-arginine supplementation may improve ovarian response, endometrial receptivity and pregnancy rate.

Erectile dysfuntion (ED)

Nitric oxide is required for the dilation of blood vessels needed for normal erection. In preliminary studies, men with ED found improvements in their condition when they were given supplements of L-arginine.

Promising research has found that oral administration of L-arginine in combination with pycnogenol causes a significant improvement in sexual function in men with ED without any side effects.

Interstitial cystitis

Interstitial cystitis is an idiopathic chronic bladder condition characterised by pelvic pain, dysuria, urinary frequency, and pressure in the bladder and pelvis.

Studies show that nitric oxide synthase activity is decreased in the urine of patients with interstitial cystitis compared to the urine of controls. In a preliminary trial, oral L-arginine increased urinary nitric oxide synthase activity and improved interstitial cystitis symptoms. Subsequent studies conclude that oral L-arginine (1,500 mg daily) may decrease pain and urgency in a subset of patients with interstitial cystitis.

Typical dosage range:

500 – 5000mg per day (on an empty stomach)

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