The problem with this distinction is that it fails to take into account all the ways in which food means more to us than mere sustenance. We may need food, but we also desire it. When our desire for food exceeds our body's need for it, the connection between food and drugs starts coming into focus. People whose illnesses would have killed them ten, fifty, or five hundred years ago survive today because they are taking drugs that were not available to their predecessors. Addicts need drugs in another sense.
Some substances transform the body so that it requires regular doses in order to function.
Others may not fit the clinical definition of something that is physiologically addicting, but still have enough of an impact on the body that their absence is felt with the intensity of a need. Frequently, the line between sanctioned and unsanctioned drug use blurs, as when the use of prescription drugs results in addiction or when illegal substances are used for medical reasons. Yet whether drugs are used in a way that the government deems proper or not, they differ from food in one fundamental respect. Although many people may need drugs to live, this need is historically defined. The same cannot be said for drugs.