Arginine is an amino acid which plays an important role in our bodies as a precursor
of nitric oxide biosynthesized by vascular endothelium.
Its most common commercially available form is L-Arginine which is also the form naturally occurring in nature and in the human body.
The 1998 Nobel Prize in Physiology or Medicine was awarded "for discoveries concerning nitric oxide as a signalling molecule in the cardiovascular system" .
Endothelial cells are synthesizing this substance and this production decreases with age. The amounts of nitric oxide could be also too low at a young age for genetic or dietary reasons.
Nitric oxide is an autocrine and paracrine signaling molecule having vasodilatory properties, mediating inhibition of platelet activation, monocyte and leucocyte adhesion, and smooth muscle cell proliferation.
It is also very important for a control of vascular oxidative stress and gene expression .
It is currently believed that a substance previously known as EDRF (Endothelium-derived relaxing factor) is simply nitric oxide.
Arginine, a precursor of nitric oxide, is used in biosynthesis of carnitine (needed for muscle contraction) .
Until recently it was thought that in case of shortage of arginine in the diet the body could produce it in quantities sufficient to maintain health.
However, recent studies suggest that the amount of this amino acid that our body can obtain as a result of such synthesis is too small and arginine has to be supplemented .
Formulations containing Arginine can be helpful and are being used in the following health conditions:
Arginine may slow down the process of atherosclerosis , which together with the vasodilatory action may have a positive action in coronary ischaemic disease (in stable angina) and in peripheral artery disease (PAD). May also have lowering effect on elevated blood pressure .
There is a very promising research showing very good influence of Arginine in congestive heart failure (CHF).
In one of clinical studies after using high doses of Arginine in people with congestive heart failure there was an improvement in peripheral blood flow by 29%, 6 minute walking distance increase by 8%, arterial flexibility increased by 19% [18,19]. Supplementation with this amino acid improves exercise capacity in patients with chronic stable heart failure .
Other studies showed an improvement of endothelial function [18,20] and renal function [18,21] in patients with congestive heart failure taking products containing Arginine.
Because of the relaxing (dilating) effect on blood vessels (through the action of nitric oxide) supplements with Arginine may be helpful in sexual dysfunction in men  (without side effects associated with the use of pharmaceuticals ). There is also research suggesting a helpful role of Arginine in the treatment of male and female infertility .
Rising prevalence of prostate cancer and of benign prostatic hyperplasia (BPH) is causing more and more men every year to undergo urological procedures involving prostate. Erectile dysfunction is a common complication, especially after complete prostatectomy.
Arginine is a supplement potentially helpful (at least worth trying) in those cases, which one can find out not only from Internet forums but also from scientific publications .
Malfunction of vascular endothelium associated with a deficiency of nitric oxide plays role in the pathophysiology of migraine headaches.
Therefore, supplementation with arginine may help the symptoms .
DIABETES TYPE I AND II
The level of Arginine is usually too low in people with diabetes.
Taking Arginine had a positive impact on the restoration of normal vascular function in patients with type I diabetes .
The beneficial effect of supplementation with this amino acid was also observed in type II diabetes.
Administration of Arginine may increase production of insulin by the pancreas , reduce insulin resistance, improve the level of adiponectin, have a beneficial effect on metabolism and help in losing weight [14,15].
ULCERS AND ESOPHAGEAL REFLUX 
The use of Arginine has a positive effect on the immune system .
Surgery and trauma which are leading to the formation of wounds are that kind of burden to the organism in which very often there is shortage of Arginine causing too low production of nitric oxide. Supplementation of this amino acid may accelerate the wound healing  and shorten the period of hospitalization after surgery .
Bodybuilders and other athletes use supplements with Arginine believing that this amino acid may increase the production of growth hormone and thus have a beneficial effect on the growth of muscle mass.
Currently there is no research confirming that Arginine may be helpful when it is used for this purpose .
However, there is a clinical study of Italian pediatricians showing positive response to Arginine (by influencing the growth hormone) in short children before puberty .
COGNITION AND DEMENTIA/ALZHEIMER DISEASE
Due to the very important role of nitric oxide and its declining production in human body during aging process, the use of supplements with Arginine may be useful in treating age related degenerative conditions of central nervous system of which the most common are diagnosed as dementia or Alzheimer disease .
Arginine may potentiate blood pressure-lowering effect of certain pharmaceuticals, for example drugs used to treat cardiological conditions (Nitroglicerine, ACE inhibitors, diuretics) and erectile dysfunction (Sildenafil/Viagra, Cialis). Arginine may add to the effect of these pharmaceuticals .
In the case of long-term use of Arginine with potassium-sparing diuretics (n.e. amiloride, triamterene, spironolactone) it is recommended to monitor the levels of potassium in the blood (because it may be too high) .
Supplements with Arginine probably should not be taken after acute myocardial infarction.
There is a study showing worse prognosis of people taking Arginine together with appropriate pharmaceuticals following myocardial infarction comparing to placebo group .
However, there is also newer Chinese research suggesting no influence of Arginine on prognosis in case of unstable angina and acute myocardial infarction .
( Physicians' Desk Reference )
For Nutritional Supplements
Sheldon Saul Hendler, PhD, MD, FACP, FACN, FAIC
with David M. Rorvik, MS
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2Division of Nuclear Medicine and Molecular Imaging, Department of Radiology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA
3Conjugate and Medicinal Chemistry Laboratory, Division of Nuclear Medicine and Molecular Imaging, Department of Radiology,
Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA
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Division of Nuclear Medicine and Molecular Imaging, Department of Radiology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA
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1Department of Internal Medicine, Metabolic Disorders and Hypertension, Poznan University of Medical Sciences, Poznan, Poland
2Department of Human Nutrition and Hygiene, Poznan University of Life Sciences, Poznan, Poland
3Department of Dietetics and Clinical Nutrition Medical University of Białystok, Poland
4Department of Clinical Pharmacology, Poznan University of Medical Sciences, Poznan, Poland
5Department of Education and Obesity Treatment and Metabolic Disorders, Poznan University of Medical Sciences, Poznan, Poland
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Arginine is an amino acid that is used by the vascular endothelium in the biosynthesis of nitric oxide, which has very important biological functions in the body. The most significant one seems to be vasodilation caused by relaxation of smooth muscle cells in arteries.
The Nobel Prize in Physiology or Medicine 1998 was awarded "for discoveries concerning nitric oxide as a signalling molecule in the cardiovascular system".
It is currently believed that a substance previously known as endothelium-derived relaxing factor (EDRF) is actually nitric oxide.
Arginine is mostly available (as a dietary supplement) as L-Arginine, which is also the form present in nature and in the human body. When nutritional deficiency occurs Arginine probably cannot be biosynthesized and should be supplemented. The demand for Arginine (as a precursor of nitric oxide) increases with age and its insufficient amounts may be responsible for health problems associated with aging.
Supplements with Arginine are mostly used in the following conditions:
coronary artery disease (in stable angina), peripheral artery disease, atherosclerosis, hypertension, erectile dysfunction, migraine headache, for athletic performance, to improve immune functions, for wound healing which may reduce length of hospital stay after surgery.
It is recommended not to use Arginine or to use with caution (under medical supervision) in unstable angina and acute myocardial infarction.
Arginine has an additive effect when used with certain pharmaceuticals which lower blood pressure (Nitroglicerine, ACE inhibitors, diuretics, Viagra, Cialis). It is also recommended to monitor potassium level while using this supplement with potassium-sparing diuretics (amiloride, spironolactone, triamterene) because it could be elevated.