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L-Arginine / L-Ornithine

L-arginine is an amino acid with its primary metabolic role being within the urea cycle, the biochemical pathway that metabolises nitrogen and protein. L-arginine stimulates the secretion of a number of important hormones including hypothalamic corticotropin releasing factor (CRF), pituitary growth hormone, and prolactin, pancreatice insulin, glucagons, pancreozymin and polypeptide, somatostatin, aldosterone, and adrenal catecholamines.

L-arginine is the precursor for the synthesis of NO (nitric oxide) known to be present in macrophages, and is thought to mediate a number of macrophage cytotoxic actions. NO is believed to mediate many diverse physiological processes including vasorelaxation, immune responses, adhesion of leukocytes and platelets and neurotransmission. Nitric oxide plays a role in many biochemical functions including; memory, attention and increases perfusion of the kidneys, lungs and liver by enhancing blood flow.


500mg-6000mg daily.

Potential applications

Sports nutrition, exercise tolerance in cases of reduced blood flow, weight control, convalescence, recovery from surgery, sepsis and trauma, fertility and impotence, atherosclerosis, hypertension and angina.

Known contraindications

Not recommended in cases of schizophrenia or herpes infection.

Use in conjunction with

May be beneficial in weight control when combined with ornithine. May be helpful in infertility cases alongside vitamin C, EFAs, l-carnitine, and antioxidants particularly pycnogenol and/or grape seed for regulation of nitric oxide.


Take away from protein for maximum effect, ideally 30-60 minutes before or after a meal Ornithine is a precursor of arginine and when taken orally, has very similar effects.

Arginine in sexual stimulation

Sexual stimulation causes activity in the nervous system which, in turn, causes local release of nitric oxide in the genitals. This stimulates a substance called cGMP that increases blood flow causing sexual arousal. L-arginine is popular in sexual dysfunction supplements as it is required to carry out the syntheses of nitric oxide. A third of men showed improvements in a double blind placebo trial. It has not been tested on its own in women, but in combination with Panax ginseng, Ginkgo biloba, damiana and multiple vitamins and minerals, 71% reported increased sexual desire.

© Cheryl Thallon at Viridian

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