This may be off-subject for this site, but it has to do with sex. I was wondering why when men get old they "can't get it up" anymore. How does Viagra help that?

Sexual function requires good physical health and plenty of hormones. When you're young you usually have plenty of both, which is why teens and young adults can get so randy. But as you age your body slows down a bit. All due respect to the several marathon runners I know who are over 50; they could school me any day of the week. The rest of us probably won't keep in such good shape. The cardiovascular system weakens from a lifetime of stress and poor maintenance. Industrialized society has given us a lifetime of eating fatty foods, exposure to tobacco smoke and a host of things that can wreck our blood vessels in the long run. When you finally get to your "golden years," your cardiovascular system is likely not in top form. Bad cardiovascular health is a major cause of male impotence (and death, but that's beside the point). Some people become diabetic. Some people develop arthritis. Those are only a few examples of conditions that can make sex physically difficult. On top of that, testosterone production wanes in age. Testosterone is the male hormone that promotes libido (as well as a lot of other things). Older men whose testosterone levels have decreased will not desire as much sex. So there you have it: declining physical health and hormonal changes are major reasons why older men have trouble getting it up.

I'll address the problem that's most relevant to Viagra (sildenafil citrate) Cialis (tadalafil) and Levitra (vardenafil). All of these drugs allow blood vessels to relax and widen. This is important to correcting erectile dysfunction because oftentimes, cardiovascular problems in older men can make it difficult for blood to flow into the penis. Taking these drugs will relax the penile blood vessels, allow blood to flow into the penis, thus it facilitates erections.

This brings us to reasons why young men should not take drugs that treat erectile dysfunction. young men are usually in good health and little or no cardiovascular trouble. Their penile blood vessels can dilate and constrict as needed. Adding Viagra et al to the mix can result in painful, prolonged erection called priapus (aka "OMFG!!! It won't go back down!!!"). Priapus can result in permanent damage to the penis, and requires a mad dash to the emergency room to get treated.

While we're still young, we can take steps to help avoid needing Viagra in the future. There's not much we can do about waning sex hormones, but we can help prevent cardiovascular disease by:

1. Getting lots of aerobic exercise
2. Eating more fruits and vegetables and less fat and grease
3. Refraining from using tobacco and other drugs.