L-arginine (L-citrulline)

L-arginine is a semi-essential amino acid. This means that the body normally produces adequate amounts of it. However, certain people such as infants and people with particular health conditions do not produce enough of it. They therefore need to get adequate amount of l-arginine either through foods or supplements. L-arginine is commonly found in foods such as dairy products, meats, seafood, grains, nuts, seeds, peas and beans. It was first isolated in 1886 by a Swiss chemist.

L-arginine plays an important role in overall metabolism, cell division, protein synthesis, the healing of wounds, removing waste products from the body, immune function, reducing insulin resistance and supporting bone growth.

L-arginine also plays a very important role in the creation of nitric oxide, which is an essential ingredient for a man to get an erection.

There are two basic types of amino acids: essential amino acids and non-essential amino acids. Essential amino acids cannot be synthesized in the body, so they have to be obtained via foods or supplements. The non-essential amino acids on the other hand, can be synthesized in the body and therefore do not need to be provided directly by foods or supplements.

Although there are several hundred different amino acids, the most well-known are the 22 so-called proteinogenic amino acids. These are called proteinogenic because they are precursors to, or building blocks of, proteins. L-arginine is one of these proteinogenic amino acids.

When proteins are digested though foods or supplements, they are broken down into specific amino acids. These are in turn re-assembled to the proteins that the body needs the most. These newly formed proteins are then used to build and repair muscle, tissue, organs, skin, hair and other parts of the body.

Amino acids are also a source of energy, similar to fats and carbohydrates. In addition, amino acids transport nutrients and oxygen through the body, synthesize neurotransmitters, enable vitamins and minerals to perform their jobs properly, produce antibodies for the immune system, regulate gene expression and perform several other functions.

L-arginine plays a crucial role in the process whereby a man gets an erection. This is because l-arginine is necessary for the inner lining of the blood vessels (called the endothelium) to create nitric oxide. Nitric oxide is an essential element in the process that causes the penis to become erect. Without nitric oxide it would practically be impossible to have an erection. To learn more about nitric oxide on Truelibido, please go here and to learn more about the process of an erection on Truelibido, please go here.

The inner lining of the blood vessels are covered with cells that are called endothelial cells. One of the main functions of these cells is to act as gatekeepers for what is allowed to enter and exit the bloodstream. But also, within these endothelial cells, a group of enzymes operate that are called nitric oxide synthase. It is these enzymes that produce the very important gas called nitric oxide. Nitric oxide synthase produce nitric oxide by combining a nitrogen atom from l-arginine with an oxygen atom from molecular oxygen (or from another molecule containing oxygen). When these atoms are combined, nitric oxide is created.

When nitric oxide is created by nitric oxide synthase, it is diffused into the smooth muscles of the penis. This influx of nitric oxide enables these muscles which are normally in a state of contraction, to relax. This happens by nitric oxide setting off a cascade of events which culminates with a decrease of free calcium levels. It is this reduction in free calcium levels that enables the contraction of the smooth muscles to ease up and for the relaxation of these muscles to start.

When the smooth muscles in the penis are contracted, they squeeze together around the blood vessels and therefore don’t let blood enter the penis other than for maintenance purposes. When these muscles instead relax, they let go of this clamp and blood is then allowed to flow into the penis. This expansion of the blood vessels is called vasodilation. As blood flows into the penis, an erection is starting to build.

Nitric oxide is a molecule with an unpaired electron which makes it a so-called free radical. Therefore it very easily reacts with other molecules and normally has a life of only a few seconds in the human body. As a result, nitric oxide is normally not free flowing around the body, but reacts with other molecules to form more stable products such as nitrate, which can be synthesized to nitric oxide.

Some studies have been undertaken to analyze the ability of l-arginine to enhance erectile functioning, however the results are not conclusive. In one study of 32 men with erectile dysfunction, l-arginine was given orally at a dose of 3×500 mg/day for 34 days. This produced no better results than a placebo.

Another study on 50 men with erectile dysfunction, measured the impact on sexual function after orally taking 5 g/day of l-arginine. After 6 weeks, 31% of the persons taking l-arginine reported a significant improvement in sexual function. All of the persons who reported improvements, had a lower than normal production of nitric oxide before the study started. The results indicate that persons with inadequate production of nitric oxide may benefit from supplementation of l-arginine. Research also indicates that persons who have adequate levels of nitric oxide production derive little benefit from l-arginine supplements.

Also, when l-arginine is combined with other supplements such as pine bark or yohimbe, there appears to be synergistic effects and the pro-erectile effects are magnified. To learn more about combining l-arginine and pine bark on Truelibido, please go here.

Research looking at the impact of supplementing with l-arginine on expansion of blood vessels (vasodilation), have reported a significant improvement, particularly in people with inadequate nitric oxide production.

Studies done on animals also provide some indication of effectiveness. In a laboratory study, both adult and aging rats were fed l-arginine through drinking water for 8 weeks to determine whether this supplementation could stimulate penile erections. The study concluded that oral administration of l-arginine did improve the erectile response in the rats, and that penile nitric oxide synthase activity was increased nearly 100% in the l-arginine treated groups vs. the control group.

In addition to its potentially beneficial effects on libido and erectile functioning, l-arginine is also used for heart and blood vessel conditions including congestive heart failure, chest pain, high blood pressure, coronary artery disease, blood clots and stroke. Some people also use l-arginine for preventing the common cold, reducing healing time of injuries, improving athletic performance, boosting the immune system, stimulating the release of growth hormone, increasing bone strength and preventing inflammation.

l-arginine is also reported to improve sperm production and sperm motility, however there are no studies that have reported any impact on testosterone.

Some research indicates that supplementing with an amino acid called l-citrulline may in fact be more effective than supplementing with l-arginine. The reason for this is that l-arginine often gets eliminated through various reactions in the body, before it can become a building block of nitric oxide. L-citrulline however, escape most of these reactions and hence normally remains intact until it reaches the kidneys. When l-citrulline reaches the kidneys, it is then converted to l-arginine, and it can therefore be a direct donor of l-arginine. It may therefore be a more effective supplement for nitric oxide production than direct l-arginine supplementation.

One study reviewed the effects of supplementing with 1,500 mg l-citrulline in men with mild erectile dysfunction over 2 months. The study reported that 50% of the men given l-citrulline saw their erections become completely hard and fully rigid, from being in a state where they were not able to have satisfactory penetration or successful intercourse. Also, the number of sexual intercourses per month for this group increased by 68%.

My Experience

  • Form: Loose powder
  • Dose: One half-topped tablespoon (approximately 7 grams)
  • When: One hour before sexual activity
  • Effect on Libido: None
  • Effect on Erection: Good
  • Effect on Sensation: None
  • Taste: Neutral
  • Verdict: A very nice supplements
  • Noticed Side-Effects: None

When I first tried tried l-arginine, I took it in capsule form in the morning before heading to work. I recall one morning, after having taken 1.5 grams, I was sitting on the bus and I had a monster erection in my pants. It came out of nowhere and I felt I had to cover myself so I didn’t reveal what was going on. I don’t think I even had any sexual thoughts, it just came totally unexpected. To me, this was highly unusual. I mean, I was struggling with erectile dysfunction and would normally never ever get spontaneous erections.

Although I don’t know for sure why I had this erection on the bus out of nowhere, I am guessing it might have had to do with l-arginine. I say this because I have also had spontaneous erections at other times after taking this supplement.

However, taking 1.5 grams in the morning did not help me overcome my problems. Neither did taking 1.5 grams before sex. Therefore, I increased the dosage similarly to what I did for most of the herbal supplements. I started mixing one half-topped tablespoon of the powder (about 7 grams) with cold water. I stirred for a few seconds until the powder was dissolved, and then drank it. I did this about one hour before sex. To me, l-arginine has no taste, so taste-wise taking this was pretty much just like drinking water.

And taking 7 grams had a much more profound effect that taking just 1.5 grams. To me, this did produce noticeable results. Although this didn’t always result in a rock solid erection, it would normally make my erections stronger, fuller and longer lasting. I have also switched from l-arginine to a very similar supplement called l-citrulline (see above) as to me, that has produced even better results. With l-citrulline, I feel my erections are stronger and also I feel the supplement is more reliable than l-arginine. Also, l-citrulline (to me) tastes like citrus.

Although l-citrulline (or l-arginine) has helped me getting erections, I have not noticed any increase in libido or any increase in pleasurable sensations from sex after taking this supplement.

When I take supplements, I typically always take more than one because the combined effect of taking several of these supplements is typically very intense. And l-citrulline is normally always included among the ones I take. When I take an herbal supplement, I typically always also take l-citrulline, pine bark and ZMA. You can learn more about this in the section called The Solution.

Not only has l-citrulline (l-arginine) become part of the supplements I normally always take, it has been of great help to me in overcoming erectile dysfunction.

I have also never experienced any side effects from l-citrulline or l-arginine.

Research Studies

Ammann P, Laib A, Bonjour JP, Meyer JM, Rüegsegger P, Rizzoli R. Dietary essential aminoacid supplements increase the bone strength by influencing bone mass & bone microarchitecture in an isocaloric low-protein diet. J Bone Miner Res. 2002 Jul; 17(7):1264-72.

Cartledge J, Minhas S, Eardley I. The role of nitric oxide in penile erection. Expert Opin Pharmacother. 2001 Jan; 2(1):95-107.

Chauhan A, More RS, Mullins PA, Taylor G, Petch C, Schofield PM. Aging-Associated Endothelial Dysfunction in Humans Is Reversed by L-Arginine. J Am Coll Cardiol. 1996 Dec; 28(7):1796-804.

Chen J, Wollman Y, Chernichovsky T, Iaina A, Sofer M, Matzkin H. Effect of oral administration of high-dose nitric oxide donor L-arginine in men with organic erectile dysfunction: results of a double-blind, randomized, placebo-controlled study. BJU Int. 1999 Feb; 83(3):269-73.

Cormio L, De Siati M, Lorusso F, Selvaggio O, Mirabella L, Sanguedolce F, Carrieri G. Oral citrulline supplementation improves erection hardness in men with mild erectile dysfunction. Urology 2011 Jan; 77(1):119-22.

Jung HC, Mun KH, Park TC, Lee YC, Park JM, Huh K, Seong DH, Suh JK. Role of nitric oxide in penile erection. Yonsei Med J. 1997 Oct; 38(5):261-9.

Kim NN, Christianson DW, Traish AM. Role of arginase in the male and female sexual arousal response. J Nutr. 2004 Oct; 134(10 Suppl):2873S-2879S; discussion 2895S.

Kim NN, Cox JD, Baggio RF, Emig FA, Mistry SK, Harper SL, Speicher DW, Morris SM Jr, Ash DE, Traish A, Christianson DW. Probing erectile function: S-(2-boronoethyl)-L-cysteine binds to arginase as a transition state analogue and enhances smooth muscle relaxation in human penile corpus cavernosum. Biochemistry. 2001 Mar 6; 40(9):2678-88.

Klotz T, Mathers MJ, Braun M, Bloch W, Engelmann U. Effectiveness of oral L-arginine in first-line treatment of erectile dysfunction in a controlled crossover study. Urol Int. 1999; 63(4): 220-3.

Lebret T, Herve JM, Gorny P, Worcel M, Botto H. Efficacy and safety of a novel combination of L-arginine glutamate and yohimbine hydrochloride: a new oral therapy for erectile dysfunction. Eur Urol. 2002 Jun; 41(6):608-13; discussion 613.

Merimee TJ, Lillicrap DA, Rabinowitz D. Effect of arginine on serum-levels of human growth-hormone. Lancet. 1965 Oct 2;2(7414):668-70.

Moody JA, Vernet D, Laidlaw S, Rajfer J, Gonzalez-Cadavid NF. Effects of long-term oral administration of L-arginine on the rat erectile response. J Urol. 1997 Sep; 158(3 Pt 1): 942-7.

Morales ME, Rico G, Bravo C, Tapia R, Alvarez C, Méndez JD. Progressive motility increase caused by L-arginine and polyamines in sperm from patients with idiopathic and diabetic asthenozoospermia. Ginecol Obstet Mex. 2003 Jun; 71:297-303.

Palloshi A, Fragasso G, Piatti P, Monti LD, Setola E, Valsecchi G, Galluccio E, Chierchia SL, Margonato A. Effect of Oral L-arginine on Blood Pressure and Symptoms and Endothelial Function in Patients With Systemic Hypertension, Positive Exercise Tests, and Normal Coronary Arteries. Am J Cardiol. 2004 Apr 1; 93(7):933-5.

Piatti PM, Monti LD, Valsecchi G, Magni F, Setola E, Marchesi F, Galli-Kienle M, Pozza G, Alberti KG. Long-term oral L-arginine administration improves peripheral and hepatic insulin sensitivity in type 2 diabetic patients. Diabetes Care, Volume 24, issue 5, (pp. 875-880).

Scibona M, Meschini P, Capparelli S, Pecori C, Rossi P, Menchini Fabris GF. L-arginine and male infertility. Minerva Urol Nefrol. 1994 Dec; 46(4):251-3.

Schwedhelm E, Maas R, Freese R, Jung D, Lukacs Z, Jambrecina A, Spickler W, Schulze F, Böger RH. Pharmacokinetic and pharmacodynamic properties of oral L-citrulline and L-arginine: impact on nitric oxide metabolism. Br J Clin Pharmacol 2008; 65:51-9.

Stanislavov R, Nikolova V. Treatment of erectile dysfunction with pycnogenol and L-arginine. J Sex Marital Ther. 2003 May-Jun; 29(3):207-13.

Toda N, Ayajiki K, Okamura T. Nitric oxide and penile erectile function. Pharmacol Ther. 2005 May; 106(2):233-66.

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