Saltpeter

The chemical compound of potassium nitrate - better known as saltpeter - apparently has an undeserved reputation. The rumor has persisted for decades among men or boys housed together in boarding schools, prisons, or army barracks that it is added to the food to suppress sexual urges. During World War I and II, for instance, it was believed that government-issued cigarettes were soaked in saltpeter. It is in fact used in the manufacture of cigarettes - but to ensure an even burn, not to douse one's flame, so to speak. While saltpeter is used to make (ahem) explosives and may be prescribed for asthma because it relaxes involuntary muscle fiber, both The Straight Dope and Snopes state that it is not an anaphrodisiac. If you are not convinced, avoid corned beef, ice cream, and toothpaste for sensitive teeth. If, however, you'd like to put it to the test, you can purchase it here.