Arginine was first isolated from the extract of lupin seedlings by the German chemist Ernst Schultze in 1886.
Arginine in nature
Arginine is found naturally in a variety of foods, including turkey, pork, chicken, pumpkin seeds, soybeans, peanuts, spirulina, chickpeas, and lentils.
Potential health benefits
Arginine (also known as L-Arginine) is an important amino acid found in food, and is one of three compounds that create creatine, a molecule involved in the cellular energy system that produces adenosine triphosphate (ATP), a form of energy for cellular functions. In both humans and mammals, approximately 80% of the nitrogen excreted is in the form of urea, which is produced via a series of reactions occurring in the liver. These reactions are collectively called the urea cycle or the Krebs-Henseleit cycle. Arginine is an intermediary in the urea cycle with L-ornithine, L-citrulline, and argininosuccinate. Ammonia is produced as part of nitrogen metabolism and is toxic, so it should be removed from our body. The urea cycle converts ammonia into urea in the liver; it then enters the bloodstream, is filtered by the kidneys, and then excreted as urine.
Arginine plays an essential role in this chain of events, facilitating the removal of ammonia from the body. Arginine is also a popular sports supplement used by athletes, as it directly produces nitric oxide via the nitric oxide synthase enzymes. However, this effect seems to be inconsistent: whilst there have indeed been studies that have shown an increase of nitric oxide, other studies have shown no effect whatsoever[2-3]. This inconsistency may result from the poor absorption of arginine by the intestines. L-Citrulline is a possible alternative that has superior absorption and is able to increase levels of arginine at a higher level and longer duration than L-Arginine supplementation.
However, despite the unreliable results, arginine persists as a favorite for sports and athletics enthusiasts. Arginine helps to produce the byproduct agmatine, a signalling molecule shown to regulate multiple molecular targets, including neurotransmitters, and ion channels. Agmatine also plays a role in nitric oxide (NO) synthesis in combination with ornithine and argininosuccinate, which widens and relaxes the blood vessels, improving blood flow.
In a research study, a combination of arginine and citrulline in patients with hypertension reduced systolic and diastolic blood pressure in both ankle and brachial measurements. Another study looked at patients with peripheral artery disease, where an infusion of arginine was able to double blood flow to extremities. Impressively, it performed on par with prostaglandin E1, a commercial drug designed to induce vasodilation (widening of the blood vessels). A significant increase of nitric oxide was also noted by the researchers during the study. In a follow-on study, these benefits were observed with oral supplementation of arginine as well.
There is some suggestion that nitric oxide signalling might also have a role in aging, mainly due to inflammation. Inflammation increases levels of inducible nitric oxide synthase (iNOS), resulting in increased oxidative byproducts such as peroxynitrite, which causes neurotoxicity. More research is needed in this area before we have a complete picture of its role in the aging process, but it is likely a downstream effect of the primary aging processes.
This article is only a very brief summary, and is not intended as an exhaustive guide and is based on the interpretation of research data, which is speculative by nature. This article is not a substitute for consulting your physician about which supplements may or may not be right for you. We do not endorse supplement use or any product or supplement vendor and all discussion here is for scientific interest.
 Guoyao, W. U., & Morris, S. M. (1998). Arginine metabolism: nitric oxide and beyond. Biochemical Journal, 336(1), 1-17.
 Liu, T. H., Wu, C. L., Chiang, C. W., Lo, Y. W., Tseng, H. F., & Chang, C. K. (2009). No effect of short-term arginine supplementation on nitric oxide production, metabolism and performance in intermittent exercise in athletes. The Journal of nutritional biochemistry, 20(6), 462-468.
 Bailey, S. J., Winyard, P. G., Vanhatalo, A., Blackwell, J. R., DiMenna, F. J., Wilkerson, D. P., & Jones, A. M. (2010). Acute L-arginine supplementation reduces the O2 cost of moderate-intensity exercise and enhances high-intensity exercise tolerance. Journal of Applied Physiology, 109(5), 1394-1403.
 Figueroa, A., Sanchez-Gonzalez, M. A., Wong, A., & Arjmandi, B. H. (2012). Watermelon extract supplementation reduces ankle blood pressure and carotid augmentation index in obese adults with prehypertension or hypertension. American journal of hypertension, 25(6), 640-643.
 Bode-Böger, S. M., Böger, R. H., Alfke, H., Heinzel, D., Tsikas, D., Creutzig, A., … & Frölich, J. C. (1996). L-Arginine induces nitric oxide–dependent vasodilation in patients with critical limb ischemia. Circulation, 93(1), 85-90.
 Böger, R. H., Bode-Böger, S. M., Thiele, W., Creutzig, A., Alexander, K., & Frölich, J. C. (1998). Restoring vascular nitric oxide formation by L-arginine improves the symptoms of intermittent claudication in patients with peripheral arterial occlusive disease. Journal of the American College of Cardiology, 32(5), 1336-1344.
 Calabrese, V., Mancuso, C., Calvani, M., Rizzarelli, E., Butterfield, D. A., & Stella, A. M. G. (2007). Nitric oxide in the central nervous system: neuroprotection versus neurotoxicity. Nature Reviews Neuroscience, 8(10), 766-775.