Amino-Acids: L-Arginine

L-Arginine or just arginine is a semi-essential amino-acid or conditionally essential amino acid depending on the health status and developmental stage of the person. Only in small children are they unable to synthesize or produce arginine internally. We obtain most of our arginine from protein-containing foods such as dairy and meat foodstuffs but this is not convenient to all. It is synthesized in our body from glutamine via citrulline.

Sources

Runners take L-arginine to help with muscle repair as well as generate nitric oxide.
Photo by Skeeze, c/o Pixabay.

The amino acid was isolated in 1886 from seeds and goat horns. It is so called because the ancient Greek for silver is argiros and the product has a silvery-white appearance.

Arginine is usually available in a pure, free-form which is absorbed in the digestive system without the need for enzymes. A number of suppliers offer arginine in different formats, usually capsules for ease of swallowing or as a powder to add to drinks and other products for supplementation. L-arginine is usually available in its own right, as a salt of the alpha-ketoglutarate. We suggest a few from well established suppliers such as Solgar and Swanson in the two main formats, capsules or powders.

Production Of Nitric Oxide

Not only is arginine one of the building blocks of proteins it is the precursor for making nitric oxide (NO) which helps blood vessels relax and reduce blood pressure (Schmidt et al., 1988). NO is thus a signalling molecule produced in the endothelium of blood vessels.

Relaxation of blood vessels is known as vasodilation and important for maintenance of blood flow throughout the body. That means it helps lessen the burden on our heart and improve cardiovascular performance.

One other function related to arginine supplementation on NO. Increasing blood flow is triggered by a biochemical cascade. Various cellular reactions trigger relaxation of the smooth muscle walls of blood vessels. This causes widening or dilation to improve blood flow. Hence, the outcome is reduced blood pressure too.

NO also improves mitochondrial respiration and platelet function.

There is scientific evidence that supplementation with arginine and L-citrulline together are better promoters of NO production (Sureda and Pons, 2012).

Thermogenesis

Arginine is one of those compounds that can initiate thermogenesis which is heat production by the body to keep cellular systems running through increasing energy use.

Arginine also has a role in maintaining a healthy immune system (Barbul, 1990). The amino acid is required for the detoxification of ammonia from nitrogen catabolism.

Arginine is very popular with sports people, body builders and those of us using exercise regimes that turn fat to muscle.

Muscle Repair Following Injury

Arginine is claimed to assist in the healing and repair of muscles following severe exercise. One study now suggests that arginine does not improve muscle function when recovering from strength exercises (Andrade et al., 2018). However, one study does not cuawe a gaping hole in the theory.

A few animal studies demonstrated that when their muscle was damaged through strain injuries, there was haemorrhage and oedema. Feeding animals L-arginine helped with faster muscle repair by encouraging more rapid collagen fibre proliferation and angiogenesis. {Angiogenesis is the physiological process through which new blood vessels form from pre-existing vessels}.

The generation and formation of new blood vessels creates better blood flow to the damaged muscle. Also, there is better healing from improved transport of oxygen and nutrients to the affected parts with the concomitant ease of removal of waste and damage-related products.

Safety

WARNING: Not intended for use by children or pregnant women. In case you suffer from a kidney or liver disease, consult your physician before use. Reduce your daily dose if you experience nausea, abdominal cramps or diarrhoea.

A number of toxicology and safety assessments with animal models including rats have established daily safety limits. The consensus is that L-arginine is metabolised fully by 5 hours if not used for the purpose it was intended. A dose of 4 to 5g per day is typical based on normal dietary estimates. For serious atheletes, 6 to 15g per day for a 70kg adult is adequate in the long term. For most sporting purposes, 3g per day extra is fine for marathon runners.

It may also increase virus growth if you have a herpes simplex virus. Supplementation can also increase headaches, weakness and diarrhea.

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References

Andrade, W.B., Jacinto, J.L., da Silva, D.K., Roveratti, M.C., Estoche, J.M., Oliveira, D.B., Balvedi, M.C.W., da Silva, R.A. and Aguiar, A.F., (2018) L-arginine supplementation does not improve muscle function during recovery from resistance exercise. Applied Physiology, Nutrition, and Metabolism, (ja). http://www.nrcresearchpress.com/doi/abs/10.1139/apnm-2017-0594#.WrE0h-jFKUk

Barbul, A. (1990). Arginine and immune function. Nutrition (Burbank)6(1), pp. 53-58.

Bescos, R., Gonzalez-Haro, C., Pujol, P., Drobnic, F., Alonso, E., Santolaria, M.L., Ruiz, O., Esteve, M., Galilea, P. (2009) Effects of dietary l-arginine intake on cardio-respiratory and metabolic adaptation in athletes. Int. J. Sport Nutr. Exerc. Metab. 19 pp. 355-365

Bloomer, R.J. (2010) Nitric oxide supplements for sports. J. Strength Cond. Res. 32 pp. 14-20

Nakhostin-Roohi, B., & MohammadiAghdam, Z. (2017). The effect of L-Arginine supplementation on Delayed Onset Muscle Soreness (DOMS) after eccentric heavy exercise. Bimonthly Journal of Hormozgan University of Medical Sciences21(3), pp. 169-177.

Pahlavani, N., Entezari, M. H., Nasiri, M., Miri, A., Rezaie, M., Bagheri-Bidakhavidi, M., & Sadeghi, O. (2017). The effect of l-arginine supplementation on body composition and performance in male athletes: a double-blinded randomized clinical trial. European journal of clinical nutrition71(4), pp. 544.

Pahlavani, N., Jafari, M., Sadeghi, O., Rezaei, M., Rasad, H., Rahdar, H. A., & Entezari, M. H. (2014). L-arginine supplementation and risk factors of cardiovascular diseases in healthy men: a double-blind randomized clinical trial. F1000Research3.

Schmidt, H.H., Nau, H., Wittfoht, W., Gerlach, J., Prescher, K.E., Klein, M.M., Niroomand, F., Bohme, E (1988) Arginine is a physiological precursor of endothelium-derived nitric oxide. Eur. J. Pharmacol. 154 pp. 213-216

Sureda, A., Pons, A. (2012)  Arginine and Citrulline Supplementation in Sports and Exercise: Ergogenic Nutrients? Lamprecht M (ed): Acute Topics in Sport Nutrition. Med Sport Sci. Basel, Karger, vol. 59, pp 18–28 https://www.karger.com/Article/Abstract/341937