Taking L-cittrilline supplements can improve erection hardness in men with mild erectile dysfunction, according to a study conducted by researchers at University of Foggia in Foggia, Italy.

L-arginine supplementation has been known to improve nitric oxide-mediated vasodilation and endothelial function which are important for blood flow and erectile hardness.  L-citrilline is converted to L-arginine in the body and for that reason, L-citrilline should theoretically work as well as L-arginine.

In the study, men aged 56 years old with mild erectile dysfunction took placebo or L-citrilline in a dose of 1.5 grams per day for one month.  Erectile hardness, number of intercourses per month, treatment satisfaction, and adverse effects were compared before and after supplementation.

The trial results show that 50% of men who took L-citrilline supplements normalized erectile hardness (from score 3 to score 4), compared with 8% of men who took placebo.  Men who took L-citrilline supplements increased the number of intercourses.  And all of those who reported an improvement in erectile hardness said they were very satisfied with the treatment.  No men using L-citrilline reported any adverse effects, suggesting that the supplement is safe to use for a short term.

The study report notes that L-citrilline supplements were less effective than phosphodiesterase type-5 enzyme inhibitors like Viagra, which effectively make the blood flow easier by maintaining high levels of vasodilation-promoting nitric oxide (NO).  However, the researchers say that short term L-citrilline supplementation has been proved to be safe and easier for some patients to accept. (David Liu)

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. doi: 10.1016/j.urology.2010.08.028.