Arginine is classified as a semi, conditionally essential amino acid. It is nonessential in nature, but becomes essential in times of extreme stress. The body’s ability to synthesize this amino acid is lost during these traumatic periods. Adequate dietary intake is therefore necessary to meet the increased physiological need.
Synthesized in the kidney, arginine is a vital amino acid, critical for numerous metabolic processes. Processes such as nitrogen catabolism, the Krebs-Henseleit urea cycle, and detoxification of ammonia are directly dependent upon arginine. It also serves as a precursor to a host of hormones, neurotransmitters, and proteins. Arginine may also be used for biological energy if glycogen is needed by the body.
Supplemental L-arginine is also acknowledged for its antioxidant properties, immunological benefit, and wound repair activity. It shows great promise in the prevention of cardio vascular disorders (e.g. atherosclerosis, angina pectoris), supporting male infertility, and aids in both kidney and liver functioning. Claims that L-arginine supplementation enhances the reduction of body fat and increases both lean muscle mass and exercise performance are, however, unsubstantiated.
The majority of arginine is derived from plant and animal proteins. The highest concentrations are found in plant and soy proteins, rather than animal protein (which is typically richer in other amino acids). The average daily intake of arginine ranges from 3 - 5 grams (g). Serving sizes below are based upon 100 grams of a given food source and are expressed in milligrams, representing the amount of arginine contained.
|Vegetables and Vegetable Products|
|4246||Spinach, frozen, chopped or leaf, unprepared|
|3506||Spinach, frozen, chopped or leaf, cooked, boiled, drained, without salt|
|3506||Spinach, frozen, chopped or leaf, cooked, boiled, drained, with salt|
|3286||Seaweed, spirulina, raw|
|2861||Seaweed, spirulina, dried|
|Nut and Seed Products|
|4466||Seeds, sesame flour, low-fat|
|4057||Seeds, cottonseed flour, low fat (glandless)|
|3616||Seeds, cottonseed meal, partially defatted (glandless)|
|3131||Seeds, sesame flour, partially defatted|
|3111||Seeds, sunflower seed flour, partially defatted|
|3082||Seeds, cottonseed flour, partially defatted (glandless)|
|Legumes and Legume Products|
|4157||Soy protein isolate, potassium type, crude protein basis|
|4093||Soy protein isolate, potassium type|
|3947||Soy protein isolate|
|3819||Peanut flour, defatted|
|3455||Soy protein isolate, Protein Technologies International, Supro|
|3422||Soy protein isolate, Protein Technologies International, ProPlus|
|Finfish and Shellfish Products|
|3805||Crustaceans, crab, alaska king, raw|
|3690||Crustaceans, shrimp, mixed species, cooked, moist heat|
|3656||Crustaceans, lobster, northern, cooked, moist heat|
|3649||Crustaceans, lobster, northern, raw|
|3626||Crustaceans, crab, blue, raw|
|3623||Crustaceans, crab, blue, canned|
|3619||Crustaceans, crayfish, mixed species, wild, raw|
|3603||Mollusks, whelk, unspecified, raw|
|3597||Crustaceans, crab, queen, cooked, moist heat|
|3597||Crustaceans, crayfish, mixed species, farmed, raw|
|3592||Crustaceans, crab, queen, raw|
|3590||Mollusks, whelk, unspecified, cooked, moist heat|
|3569||Crustaceans, crayfish, mixed species, wild, cooked, moist heat|
|3539||Crustaceans, crab, dungeness, cooked, moist heat|
|3538||Crustaceans, crab, dungeness, raw|
|3513||Crustaceans, crayfish, mixed species, farmed, cooked, moist heat|
|3485||Crustaceans, crab, alaska king, cooked, moist heat|
|3461||Crustaceans, crab, blue, cooked, moist heat|
|3361||Crustaceans, shrimp, mixed species, canned|
|3350||Crustaceans, shrimp, mixed species, raw|
|3222||Crustaceans, spiny lobster, mixed species, cooked, moist heat|
|3213||Crustaceans, spiny lobster, mixed species, raw|
|3000||Mollusks, cuttlefish, mixed species, raw|
|3000||Mollusks, cuttlefish, mixed species, cooked, moist heat|
|3125||Turkey, fryer-roasters, light meat, meat only, raw|
|3107||Turkey, fryer-roasters, breast, meat only, cooked, roasted|
|3092||Turkey, fryer-roasters, breast, meat only, raw|
|3009||Turkey, fryer-roasters, light meat, meat only, cooked, roasted|
|2961||Turkey, fryer-roasters, wing, meat only, raw|
|2867||Turkey, young tom, light meat, meat only, raw|
|Sausages and Luncheon Meats|
|3475||Turkey, white, rotisserie, deli cut|
|3020||Turkey breast meat|
|3951||Gelatins, dry powder, unsweetened|
Arginine has been a major contributor towards the research and understanding of various diseases. Clinical applications cite the effectiveness of supplemental arginine on both physical and cognitive functioning. The L-form of arginine is recommended for supplemental assistance with regard to varying physiological conditions. 
Among the most important uses of supplemental arginine is its function within the human metabolic processes. Arginine provides the means for the metabolism of muscle, protein, and nitrogen. [3, 4] Arginine is responsible for maintaining a positive nitrogen balance within the body. It accomplishes this task by excreting excess nitrogen and acting as a mechanism for the storage and transportation of nitrogen. Arginine is equally critical for the reduction of nitrogen loss in severe trauma patients. Supplemental arginine in these individuals may enhance protein synthesis; resulting in elevated wound healing properties, and immune system functioning. [5, 6] These benefits may also be witnessed in healthy persons who supplement his/her diet with L-arginine.
Arginine may also be central in the overall health of the circulatory system. Arginine is a precursor to the neurotransmitter nitric oxide (NO). NO is responsible for the constriction and dilation of blood vessels located within the brain. Because of this, arginine (in the form of arginine pyroglutamate) may provide us with improved cognitive function.  Combined with its polyamine increasing properties, the ability for arginine to improve brain function may ultimately benefit Alzheimer’s sufferers.  Researchers have also used arginine to enhance nitric oxide metabolism in patients suffering from angina, congestive heart failure, and interstitial cystitis. 
By increasing the activity of the thymus gland, arginine may enhance immune system function.  This may prove especially beneficial in the prevention of certain types of cancers. The thymus gland is responsible for the production of T lymphocytes (T-cells), which are important constituents of immunomodulatory activity. By increasing T-cells, and reducing polyamines via arginine supplementation, it may be possible to inhibit the development of tumors and other malignancies.  Nitric oxide, activated from arginine, is also used by the immune system in combating cancer.
Research also indicates that arginine may be effective in reducing Low-Density Lipoproteins (LDLs), or bad cholesterol levels.  Arginine may also yield extremely valuable antioxidant activities. It has been shown to diminish the oxidation of LDLs and inhibit lipid peroxidation. This is critical, as the oxidation of LDL is believed to be an important first step in the formation of atheromatous deposits, especially on the innermost layer of arterial walls (atherogenesis).
Arginine may also increase levels of glucose, prolactin, and most importantly, human growth hormone (HGH). The release of human growth hormone may be influenced by arginine’s potential of blocking the secretion of somatostatin, a hormone which inhibits HGH production.  Treatment of injuries, strengthening of the immune system, lean muscle composition, and anti-aging properties; all are associated with prominent levels of HGH. Arginine may further enhance HGH release when combined (stacked) with the amino acids lysine and ornithine. 
Although it is unclear why, the elderly’s response is often better than other age groups concerning arginine supplementation and growth hormone release. 
The benefits of arginine supplementation in males may be far superior in comparison to its use in women. Because arginine is found in high concentrations in seminal fluid, it may be advantageous in treating sterility in men.  As little as four grams of arginine has proven effective in clinical research for this purpose. Some 80% percent of subjects studied, who received this dosage, reported a dramatic improvement in libido, erection, and in some female cases, pregnancy.  The motility of sperm may also be positively impacted by the supplementation of arginine.
Although there are many claims regarding arginine’s ability to enhance exercise performance and assist in the development of lean body mass, research remains unclear. Arginine does, however, play an important role in the transport, elimination, and storage of nitrogen; all of which are significant in the complex metabolic processes of muscle. The amino acid creatine, a popular nutritional supplement, is also a derivative of arginine. Clearly, the topic of arginine’s supplementation in “bodybuilding” merits further research.
Because arginine is considered a nonessential amino acid, the National Research Council’s Food and Nutrition Board has not established a Recommended Daily Allowance (RDA).
The U.S. National Academy of Sciences recommends that healthy people achieve .36 grams of highly bioavailable protein for each pound of bodyweight; equaling 0.8 grams of protein per kilogram of bodyweight.
It is uncommon for individuals to develop a deficiency of any nonessential acid. Inadequacies of arginine are rare, but have occurred. Signs and symptoms of a deficiency include; rash, hair loss, hair breakage, poor wound healing, constipation, fatty liver, hepatic cirrhosis, and hepatic coma.  In cases of severe deficiency, symptoms may include muscle weakness, impairments in liver lipid metabolism, and complications in the production of insulin and glucose.
Massive dosages of arginine often are accompanied by a coarsening and thickening of skin tissue, nausea, weakness, and diarrhea. Excessive dosages may also activate and promote viral growth. For this reason, individuals suffering from herpes, or other viral infections, should not take arginine-containing supplements.
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5. Kirk SJ, Hurson M, Regan MC, et al. Arginine stimulates wound healing and immune function in elderly human beings. Surgery 1993;114: 155-160.
6. Hendler, M.D., PhD., Sheldon Saul, The Doctor’s Vitamin and Mineral Encyclopedia (New York: 1990, Fireside), pages 209-215.
7. Dean, M.D., Ward and Morgenthaler, John, Smart Drugs & Nutrients (Menio Park: 1990, Health and Freedom Publications), page 68.
8. Smith SD, Wheeler MA, Foster HE Jr, Weiss Rm. Improvement in interstitial cystitis symptom scores during treatment with L-arginine. J Urol 1997;158:703-708.
9. Hurson M, et al. Metabolic Effects of Arginine in a Healthy Elderly Population. J Parenter Enteral Nutr. May1995;19(3):227-30.
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