It appears that garlic's ability to increase hydrogen sulfide might make it a good treatment for erectile dysfunction:

Eur J Pharmacol. 2006 Mar 27;535(1-3):280-2. Epub 2006 Mar 9
Possible role for the novel gasotransmitter hydrogen sulphide in erectile dysfunction--a pilot study.
Srilatha B, Adaikan PG, Moore PK.
Penile erectile tissue is a highly vascularised smooth muscle which hitherto has been an unexplored target for the neuromodulatory effect of hydrogen sulphide. In this study, intracavernous injection of sodium hydrogen sulphide to primates resulted in significant increases in penile length and cavernous pressure. In another set of experiments, administration of DL-propargylglycine (inhibitor of cystathionine gamma-lyase) to rats resulted in significant reduction in cavernous nerve stimulation-evoked perfusion pressure. Our pilot experiment suggests a possible role for endogenous hydrogen sulphide in erectile physiopharmacology through facilitation of nerve-mediated penile tumescence; this is confirmed by the inhibitory effect of propargylglycine on the proerectile pathway.
PMID: 16527268

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