These drugs facilitate erection by inhibiting the PDE5 enzyme, by blocking the degradation of cyclic guanosine monophosphate (cGMP) in the cavernous smooth muscles. This inhibition results in the prolonged activity of cGMP, which further decreases intracellular calcium concentrations, maintains smooth muscle relaxation and, hence, results in rigid penile erections.
The oyster has always had an aphrodisiac reputation. One reason may be that oysters have high levels of the mineral zinc, which plays an important role in the production of the male hormone testosterone, and low levels of testosterone could be one reason for erectile dysfunction. Research presented at an American Chemical Society meeting may offer another connection: Raw shellfish contain compounds that stimulate the release of sexual hormones in both men and women.
A study published in May 2014 in The Journal of Sexual Medicine found that some men can reverse erectile dysfunction with healthy lifestyle changes, such as exercise, weight loss, a varied diet, and good sleep. The Australian researchers also showed that even if erectile dysfunction medication is required, it's likely to be more effective if you implement these healthy lifestyle changes.