Study: erection supplement with L-arginine and pycnogenol works (slightly)

Men with mild erection problems, who wouldn't necessarily consider taking Viagra or Cialis, now have a non-pharmacological alternative available. Supplements containing the amino acid L-arginine and phenol-rich extracts like pycnogenol have been shown to work, according to a study by Japanese researchers that will soon be published in Phytotherapy Research.

Regular readers of this newsletter will know how sildenafil – the active ingredient in Viagra – and its chemical relatives work: they inhibit the enzyme PDE-5. This is the enzyme that breaks down the signal substance cGMP in the blood vessels. So PDE-5 blockers boost the concentration of cGMP, which causes the blood vessels to relax. In the penis this means that the erectile tissues fill more easily with blood and therefore an erection is more likely to occur.

Sex supplements usually work the other way round. Instead of inhibiting the breakdown of cGMP they boost its production. This can be done by using substances that help increase the concentration of nitrogen monoxide [NO] in the blood vessels. NO is a signalling molecule that induces the enzyme guanylate cyclase to make more cGMP.


The Japanese work for Kobayashi Pharmaceutical company. [kobayashi.co.jp] Kobayashi produces Edicare, a dietary supplement, each pill of which contains 115 mg L-arginine, 10 mg pycnogenol and 92 mg L-aspartic acid. L-arginine is a precursor of NO, and phenols like the ones found in pycnogenol stimulate the production of NO. This combination is essential. Studies have shown that arginine on its own – in a daily dose of 1.5 grams – has no effect on erections. [Urol Int. 1999; 63(4): 220-3.] [BJU Int. 1999 Feb; 83(3): 269-73.] The reason for adding L-aspartic acid to Edicare escapes us right now, but no doubt it was well thought out.

The researchers gave 24 middle-aged men with mild erection problems six pills a day for a period of eight weeks. The men had to complete a standardised questionnaire on erection problems, the IIEF-5, just before starting to take the supplements, after four weeks and at the end of the eight weeks.

Before the experiment started the men in the Edicare group scored 16, indicating that they had a mild to moderate erection problem. After eight weeks their score had climbed to 17.1, the score for a mild erection problem. The lowest score on the scale is five, the highest 25.