Experts say that aphrodisiacs can work in two ways: There are those that create sexual desire by working on the mind, and there are those that create desire by affecting parts of the body. For example, something that increases blood flow in the sex organs might simulate the feelings of sexual intercourse and have the effect of creating desire. Likewise, there are things that can make our bodies produce more of the chemicals associated with sexual desire. Something that lowers inhibitions in the mind, such as alcohol or marijuana, might also create (or allow) the desire to have sex. Sometimes, just thinking something is an aphrodisiac makes it appear to work as one.
There are also things that quell desire. These are called anaphrodisiacs.
Researchers are finding that some foods, herbs and other supplements do stimulate production of hormones or other chemicals that affect our libidos. What they don't know is whether those chemicals are produced in a high enough quantity for us to really notice the difference. There isn't much hard research in the area, primarily because libido is a somewhat difficult thing to study.
According to the FDA, aphrodisiacs have no scientific basis and are simply myth. While this may be true, many people swear by the effects of certain foods, herbs or minerals.