Arginine is required for normal spermatogenesis. Over 50 years ago, researchers found that feeding an arginine-deficient diet to adult men for 9 days decreased sperm counts by 90% and increased the percentage of non-motile sperm approximately 10-fold. Oral administration of 500 mg arginine–HCl per day to infertile men for 6–8 weeks markedly increased sperm counts and motility in a majority of patients, and resulted in successful pregnancies.
There are only very few reports on the improvement of erectile function by l-arginine administration. A study by Chen et al. revealed a significant subjective improvement in sexual function in men with organic erectile dysfunction (31% of cases) after oral intake of 5 g l-arginine for 6 weeks, but only if they had decreased NOx excretion or production. Other studies have shown that long-term oral administration of pharmacological doses of l-arginine improves the erectile response in the aging rat as well as in patients with erectile dysfunction. However, Klotz et al. reported in a controlled crossover study that oral l-arginine at 3× 500 mg/day was not better than a placebo as a first line treatment for the mixed type of impotence.
In general, studies in this area are scarce and provide inconsistent results. Further studies, particularly of long-term usage of l-arginine, are needed to distinguish the group of patients that can most benefit from this supplement. The theoretical basis of these studies is furnished by the established crucial role of NO from nerves and possibly endothelia in initiating and maintaining intracavernous pressure increase, penile vasodilatation, and penile erection that are dependent on cyclic GMP synthesised with activation of soluble guanylyl cyclase by NO in smooth muscle cells. The aphrodisiac properties of l-arginine have not been adequately studied, despite the noticeable presence of l-arginine in most aphrodisiac and sexual stimulation formulas commercially available in the international market.
Other than the benefits in the above stated conditions, l-arginine has been demonstrated to improve:
The antioxidant property of l-arginine has been well documented in several reports. An interesting article by Grasemann et al. has demonstrated an acute and transient improvement of pulmonary function in cystic fibrosis patients by a single inhalation of l-arginine. Nebulised l-arginine significantly increased