Give men with erection problems 250 mg daily of propionyl-L-carnitine together with 2500 mg L-arginine and their sex life will improve. Researchers at the Sapienza University of Rome discovered this when they did experiments with 54 men aged between 35 and 75.
In the Italian study, which will be published soon in Andrologia, the men were given a powder containing the two amino acids plus 20 mg of the vitamin B3 analogue niacin. That's a low amount; multi-vitamin tablets usually contain more. The men dissolved the powder in a glass of water and drank this. The powder was supplied by Sigma-Tau, a manufacturer of carnitine analogues. The manufacturer's name crops up surprisingly often in studies on the positive health effects of carnitine.
The Andrologia article does not mention who funded the Italian study.
L-Arginine is a precursor of NO. NO enhances the activity of the enzyme guanylate cyclase in the blood vessels, which in turn raises the concentration of cyclic guanosine monophosphate [cGMP]. CGMP helps blood vessel walls to relax. Erection medicines like Viagra and Cialis work via cGMP.
Carnitine analogues, whether or not combined with niacin, boost fatty acid combustion in cells, and therefore also in the cells of the blood vessel walls. As a result of this fewer free radicals are produced and the blood vessels become more flexible. This is how carnitine strengthens the effect of L-arginine. In theory at least.
And hey presto, it worked in the study too. After taking the supplement for three months, the average erection score [IIEF] had risen from 15 to 20. That means that the average man in the study started with an 'average to considerable' erectile dysfunction, and that improved as a result of supplementation to a 'mild' erectile dysfunction. An IIEF of 22-25 counts as healthy.
Most of the test subjects indicated that they would like to continue using the supplement. Few side effects were observed.
"In addition to first-line treatment in selected patients, the formulation tested may have a role as adjuvant therapy", the researchers conclude.
Andrologia. 2011 Oct 4. doi: 10.1111/j.1439-0272.2011.01234.x. [Epub ahead of print].