Monograph

L-Arginine may help maintain healthy cholesterol and blood pressure levels, support metabolic function, and strengthen immunity. This amino acid stimulates the secretion of metabolic hormones, including glucagon, insulin, and growth hormone and helps oxygen reach the heart by dilating blood vessels during nitric oxide synthesis. L-Arginine is a valuable aid for supporting essential physiological functions.
 

Description

L-Arginine is a semi-essential amino acid that can be naturally produced by the body; yet, supplementation may be needed for certain physiological conditions that make it difficult for the body to synthesize L-Arginine.

Research

Immune Function

L-Arginine improves immunity among patients undergoing medical treatments that weaken the immune system.[1] Research suggests L-Arginine can stimulate children's immune systems to ward off recurrent infections. A two-month study recruited 40 children, between 2 to 13 years old, with recurrent air passage infections to observe L-Arginine's role in reducing infections. Results indicated patients taking L-Arginine had significant improvement in immunity and were protected from airway infections, without any side effects.[2]

L-Arginine can also improve wound healing. Male mice with abdominal wounds received L-Arginine, which protected wound immune cell function by reducing inflammation at the wound site.[3]

Cardiovascular Health

L-Arginine has been shown to dilate blood vessels in the heart decreasing pain associated with a narrowing of the arteries. A study analyzed the effects of L-Arginine on endothelial function (maintains vascular tone and smoothness) and blood vessel dilation during exercise among 42 patients with narrowed arterial function. Results showed improvement in the L-Arginine group concerning endothelial function and exercise tolerance as platelet aggregation (excessive clumping of platelets) was reduced among this group.[4]

Adequate levels of L-Arginine need to be present for the production of nitric oxide that is vital to regular cardiovascular function. Nitric oxide aids the underlying tone and relaxation of the vessels to support normal endothelial function. A reduced production of nitric oxide causes inadequate dilation and blood flow in the arteries leading to plaque formation. A study recruited 29 subjects with reduced cardiovascular function to take L-Arginine for one week. The study found improvement in endothelial function and a reduction in blood pressure levels.[5]

Another study examined L-Arginine's role in kidney and cardiovascular health, as organ dysfunction can be caused by oxidative stress, endothelial dysfunction, and inflammation. Subjects with kidney and cardiovascular ailments were given L-Arginine for one month finding improvement in normal kidney and cardiovascular function.[6]

Balance Blood Pressure

L-Arginine can improve vascular function and normalize blood pressure. A three-week study gave rats with abnormal blood pressure L-Arginine finding a significant reduction in blood pressure and improved vascular activity.[7]

Elevated blood pressure during pregnancy can cause maternal and infant illness. One study used L-Arginine to treat pregnant rats that had abnormal blood pressure levels finding the treatment lowered blood pressure to normal ranges and reduced excessive amounts of protein in the blood.[8]

Pregnant women with blood pressure imbalances were given 4g/day of L-Arginine for two weeks finding supplementation extended pregnancy and lowered blood pressure levels.[9]

Balance Cholesterol

Unbalanced cholesterol levels can cause endothelial dysfunction and increase oxidative stress. L-Arginine normalizes endothelial function by reducing oxidative stress in individuals with high cholesterol levels. Male subjects with high levels of cholesterol were compared to male individuals with normal cholesterol levels to understand the effects of L-Arginine on normalizing vascular function. A significant improvement was seen in patients with cholesterol imbalances, as restoring the nitric oxide balance provided antioxidant benefits to reduce oxidative stress in vascular function.[10]

Decreased blood flow in the arteries that is caused by elevated cholesterol can affect the vascular activity of nitric oxide. Reestablishing nitric oxide synthesis can restore normal endothelium and platelet function to improve heart health. Patients with abnormal cholesterol levels received 8.4 g/day of L-Arginine, or a placebo. Subjects taking L-Arginine had modest improvement in blood platelet activity as nitric oxide levels were restored.[11]

A three-week study recruited male subjects with cholesterol imbalances to take L-Arginine. Results indicated L-Arginine significantly reduced excessive homocysteine levels that damage arterial lining and increase the formation of blood clots.[12]

Metabolic Function

L-Arginine has an influence on several hormonal functions, including growth hormone, glucagons, prolactin, and plasma insulin. These effects impact metabolic function, as L-Arginine aids the production of nitric oxide and has a role in glucose, fatty acid, and amino acid synthesis. An inhibition of nitric oxide can cause excessive fat production and storage in insulin-sensitive tissues. One study suggests L-Arginine may reduce fat mass by restoring the circulation of nitric oxide.[13]

Preliminary studies suggest L-Arginine's role in metabolic function may even alter insulin sensitivity and capillary growth in muscle metabolism enhancing the effects of exercise training.[14]

Another study reviewed the increase of growth hormone during exercise with a dose range of 5 to 9 g of L-Arginine treatment. Results indicated a 200% increase in growth hormone when L-Arginine supplementation was combined with exercise training.[15]

L-Arginine can even normalize hormonal stress responses in conjunction with L-lysine, another amino acid. A clinical trial with L-Arginine (2.64 g/day) and L-lysine (2.64 g/day) was administered to 108 healthy adults to observe the effects on stress reduction. The treatment reduced high levels of mental stress and anxiety, along with a reduction in salivary cortisol levels in male subjects.[16]

Additional Information – Dosage & Interactions

Suggested Use

As a dietary supplement, take one capsule, or as directed by a physician.

Dosage

Up to 15 g per day

Precautions

The maximum safe dosage of this supplement has not been determined for children, pregnant or nursing women, or those with severe liver or kidney disease. As with all supplement regimens, please consult your physician prior to use.

The most common adverse reactions occur at higher doses (15 to 30 g per day), which include nausea, diarrhea, and abdominal cramps. Pregnant and nursing mothers should avoid L-Arginine supplementation as it may stimulate growth hormone.

Drug Interactions

Consult your physician before supplementing with L-Arginine if you are taking the following medications.

Diuretics (Aldactone, Midamor, Dyazide, etc.); Estrogen (Premarin, Estrace, etc.); Ibuprofen; Sildenafil Citrate; Cyclosporine; Organic Nitrates

*Statements made herein have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure, or prevent any disease.

References

[1] Daly, JM, et al. Enteral nutrition with supplemental arginine, RNA, and omega-3 fatty acids in patients after operation: immunologic, metabolic, and clinical outcome. Surgery. 1992; 112:56-67.

[2] Baligan, M, Giardina, A, et al. L-Arginine and immunity. Study of pediatric subjects. Minerva Pediatr. 1997 Nov; 49(11):537-542.

[3] Angele, MK, Nitsch, SM, et al. L-Arginine: a unique amino acid for improving depressed wound immune function following hemorrhage. Eur Surg Res. 2002; 34(1-2):53-60.

[4] Sozykin, AV, Noeva, EA, et al. Effect of L-Arginine on platelet aggregation, endothelial function adn exercise tolerance in patients with stable angina pectoris. Ter Arkh. 2000; 72(8):24-27.

[5] Miller, AL. The effects of sustained-release-L-Arginine formulation on blood pressure and vascular compliance in 29 healthy individuals. Altern Med Rev. 2006 Mar; 11(1):23-29.

[6] El-Mesallamy, HO, Abdel Hamid, SG, Gad, MZ. Oxidative stress and asymmetric dimethylarginine are associated with cardiovascular complications in hemodialysis patients: improvements by L-Arginine intake. Kidney Blood Press Res. 2008; 31(3):189-195.

[7] Bagnost, T, Berthelot, A, et al. Treatment with the arginLase inhibitor N(omega)-hydroxy-nor-L-Arginine improves vascular function and lowers blood pressure in adult spontaneously hypertensive rat. J Hypertens. 2008 Jun; 26(6):1110-1118.

[8] Altun, ZS, Uvsal, S, Guner, G, et al. Effects of oral L-Arginine supplementation on blood pressure and asymmetric dimethylarginine in stress-induced preeclamptic rats. Cell Biochem Funct. 2008 Jun; 26(5):648-653.

[9] Facchinetti, F, Saade, GR, Neri, I, et al. L-Arginine supplementation in patients with gestational hypertension: a pilot study. Hypertens Pregnancy. 2007; 26(1):121-130.

[10] Kawano, H, Motoyama, T, et al. Endothelial dysfunction in hypercholesterolemia is improved by L-Arginine administration: possible role of oxidative stress. Atherosclerosis. 2002 Apr; 161(2):375-380.

[11] Wolf, A, Zalpour, C, Theilmeier, G, et al. Dietary L-Arginine supplementation normalizes platelet aggregation in hypercholesterolemic humans. J Am Coll Cardiol. 1997 Mar; 29(3):479-485.

[12] West, SG, Likos-Krick, A, et al. Oral L-Arginine improves hemodynamic responses to stress and reduces plasma homocysteine in hypercholesterolemic men. J Nutr. 2005 Feb; 135(2):212-217.

[13] Johgen, WS, Fried, SK, Fu, WJ, et al. Regulatory role for the arginine-nitric oxide pathway in metabolism of energy substrates. J Nutr Biochem. 2006 Sep; 17(9):571-588.

[14] McConnel, GK. Effects of L-Arginine supplementation on exercise metabolism. Curr Opin Clin Nutr Metab Care. 2007 Jan; 10(1):46-51.

[15] Kanaley, JA. Growth hormone, arginine and exercise. Curr Opin Clin Nutr Metab Care. 2008 Jan; 11(1):50-54.

[16] Smriga, M, Ando, T, Akutsu, M, et al. Oral treatment with L-lysine and L-Arginine reduces anxiety and basal cortisol levels in healthy humans. Biomed Res. 2007 Apr; 28(2):85-90.