L- Arginine

What is it and where does it come from?
Arginine is a semi-essential amino acid. It is a building block of protein that performs a myriad of physiological functions. It is a known precursor of the gas nitric oxide [N02].
Arginine is an amino acid that the body cannot make naturally. Therefore it is important to consume foods that are rich in arginine.1
Arginine is found in high concentrations in nuts and seeds like peanuts and almonds. It can also be found in chocolate and raisins.
What does it do and what scientific studies give evidence to support this?
Arginine is necessary for the execution of many physiological processes. These physiological processes include hormone secretion, an increase in growth hormone output, the removal of toxic waste products from the body, and immune system defenses.2

Because Arginine is a precursor of nitric oxide [which is responsible for vasodiolation 3] it is often used for supporting healthy sexual function.
Recently, dietary supplements containing Arginine have become popular due to Arginine's nitric oxide producing ability, its ability to scavenge free radicals, as well as its ability to signal muscle cells, release growth hormone, support healthy cholesterol, and enhance fat metabolism. Arginine helps regulate salt levels in the body. 4
For this reason it should be of interest to competing bodybuilders, as retaining water under the skin can make one looks smooth, bloated and washed out. The nitrogen retaining abilities of Arginine are well-known within the bodybuilding and scientific communities. Arginine is also believed to be crucial for muscle growth due to its vasodilating abilities, as well as its ability to participate in protein synthesis. 5
Learn more about the benefits of L-Arginine on Clayton South's Health Facts.
Who needs it and what are some symptoms of deficiency?
Everyone. Populations in particular need of arginine are growing children, infants, athletes, individuals trying to lose weight, and the elderly. In adult populations Arginine is considered to be a non-essential amino acid. For children, by contrast, Arginine is essential to the defense and development of the adolescent immune system.
Persons suffering from injury can benefit from supplemental arginine, as demand for arginine is increased during times of bodily injury and repair.6 Persons looking to support their sexual health may also benefit from use of Arginine due to its vasodilating properties. Arginine will act to increase the diameter of blood vessels, thereby allowing increased blood flow to reach constricted areas.
Arginine presents benefits to hard training athletes. Supplementing with Arginine may boost the immune system, thereby allowing the athlete to train harder and avoid the detrimental effects of minor health problems associated with overtraining.
Athletes who are discontinuing the use of androgenic or anabolic steroids may benefit from supplemental arginine.
Due to Arginines ability to increase growth hormone levels, its ability to encourage lipid oxidization, and its ability to support healthy blood pressure, supplemental arginine may prove beneficial for persons looking to lose weight.
How much should be taken? Are there any side effects?
Individuals with existing heart or psychiatric conditions should consult with their physician prior to supplementing with Arginine. With any amino acid containing product, overdose is a possibility. Dosing with too much arginine can lead to diarrhea, weakness and nausea. Clear dosing guidelines have not yet been established, so it is best to do what is known as "tolerance mapping".
Take a small dosage for one week, note the benefits and the side effects, and increase the dosage until the benefits are maximized and the side effects minimized. Over time the two will converge and you will hit the optimal dose. This process is similar to "receptor mapping" for bodybuilders who use insulin and steroids.
Many protein powders on the market are fortified with amino acids, including arginine. With this in mind, pay particular attention to how much arginine you are ingesting from sources. If you do not feel comfortable following the above described procedure, it is always best to follow the directions as prescribed on the products label.