Erections need nitric oxide, which comes from L-arginine – so taking L-arginine should boost nitric oxide levels and improve erections, right? Except it doesn’t usually work.

Part of the reason is that some of the arginine may be sent on another pathway. So, what’s the alternative?

There is L-citrulline. I always thought L-citrulline was downstream of arginine, but the study below suggests it may be better than arginine. I guess you have to read the article to find out why.

This is -as far as I know – a pretty safe (non-toxic) product that is easily available (my ideal criteria), so it is something you can try. The study below says that it can help. Presumably, it would be a good product to add on to Viagra.

Here is the abstract of the study (you can send the author an email asking for a copy of the article for free):

Cormio L, et al. Oral L-citrulline supplementation improves erection hardness in men with mild erectile dysfunction. Urology. 2011 Jan;77(1):119-22.

Department of Urology and Renal Transplantation, University of Foggia, Foggia, Italy. luigicormio@libero.it

Abstract
OBJECTIVES: To test the efficacy and safety of oral L-citrulline supplementation in improving erection hardness in patients with mild erectile dysfunction (ED). L-arginine supplementation improves nitric oxide-mediated vasodilation and endothelial function; however, oral administration has been hampered by extensive presystemic metabolism. In contrast, L-citrulline escapes presystemic metabolism and is converted to L-arginine, thus setting the rationale for oral L-citrulline supplementation as a donor for the L-arginine/nitric oxide pathway of penile erection.

METHODS: In the present single-blind study, men with mild ED (erection hardness score of 3) received a placebo for 1 month and L-citrulline, 1.5 g/d, for another month. The erection hardness score, number of intercourses per month, treatment satisfaction, and adverse events were recorded.

RESULTS: A total of 24 patients, mean age 56.5 ± 9.8 years, were entered and concluded the study without adverse events. The improvement in the erection hardness score from 3 (mild ED) to 4 (normal erectile function) occurred in 2 (8.3%) of the 24 men when taking placebo and 12 (50%) of the 24 men when taking L-citrulline (P < .01). The mean number of intercourses per month increased from 1.37 ± 0.93 at baseline to 1.53 ± 1.00 at the end of the placebo phase (P = .57) and 2.3 ± 1.37 at the end of the treatment phase (P < .01). All patients reporting an erection hardness score improvement from 3 to 4 reported being very satisfied. CONCLUSIONS: Although less effective than phosphodiesterase type-5 enzyme inhibitors, at least in the short term, L-citrulline supplementation has been proved to be safe and psychologically well accepted by patients. Its role as an alternative treatment for mild to moderate ED, particularly in patients with a psychologically fear of phosphodiesterase type-5 enzyme inhibitors, deserves further research.