Nitric Oxide Precursor L-Citrulline Involved in Men's Health

Nitric Oxide Precursor L-Citrulline Involved in Men's Health

Researchers have found that supplementation with L-citrulline supports an important aspect of men’s health.

Researchers set out to test the efficacy and safety of oral L-citrulline, a precursor of nitric oxide, in improving male health in people who were looking to support healthy sexual performance. Past studies have found that 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, explaining the rationale for oral L-citrulline supplementation as a donor for the L-arginine/nitric oxide pathway of penile erection.

In the current single-blind study, men who wanted to achieve optimal erectile function (who initially had an erection hardness score of 3) received a placebo for 1 month and L-citrulline, 1.5 gram/day, for another month. The erection hardness score, number of intercourses per month, treatment satisfaction, and adverse events were recorded.

A total of 24 patients, mean age 56.5 years, were entered into the study and concluded the study without adverse events. The improvement in the erection hardness score from 3  to 4 (normal erectile function) occurred in only 2 (8.3 percent) of the 24 men when the men were taking the placebo and 12 (50 percent) of the 24 men when the men were taking L-citrulline. 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 and 2.3 ± 1.37 at the end of the treatment phase. All patients reporting an erection hardness score improvement from 3 to 4 reported being very satisfied.

According to the researchers, “… in the short term, L-citrulline supplementation has been proved to be safe and psychologically well accepted …”

The researchers went on to state that L-citrulline’s role in safely supporting sexual health deserves further research.


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