L-Arginine - Arginine
Arginine (amino acid L-arginine) has been the focus of increasing interest since the early 1980s when its use was first popularized as a safe and effective way to increase the amount of growth hormone (GH) released from the pituitary gland.
Arginine has been heavily promoted as a health supplement capable of enhancing sexual function in men and women. Specifically, claims have been made that arginine supplementation may resolve erectile dysfunction, producting better erections in healthy men.
The study "Effects of Long-Term Oral Administration of L-Arginine on the Rat Erectile Response" performed by the Department of Surgery, Harbor-UCLA Medical Center, Torrance, California showed that argining supplementation does cause better erections in rats:
"Long-term oral administration of supra-physiologic doses of L-arginine improves the erectile response in the aging rat. We postulate that L-arginine in the penis may be a substrate-limiting factor for NOS activity and that L-arginine may up-regulate penile NOS activity but not its expression. The blockade of penile erection by electric field stimulation with N-omega-nitro-L-arginine methyl ester suggests that if ancillary corporeal vasodilator mechanisms develop, a basal level of NO synthesis is still required for activation and relaxation of the corporeal smooth muscle. These data support the possible use of dietary supplements for treatment of erectile dysfunction."
During the study, arginine-fed control rats underwent electric field stimulation of the cavernosal nerve to induce erection and maximal intracavernosal pressure was measured. An increased intracavernosal pressure will manifest itself as increased rigidity, and, if it occurs in the human male, will subjectively be interpreted as a "better" erection. The above-cited study found that indeed, long-term arginine supplementation did cause a higher intracavernosal pressure- in a rat.
Nitric oxide is needed for erections, and the enzyme nitric oxide synthase needs L-arginine to metabolize nitric oxide. The amounts of L-arginine needed, however, may be so small that the required amount is readily attained from food sources.