3.1 When does food become a drug?

The Greeks and Romans sometimes described the difference between drugs and foods as one of taste: a drug is usually much more bitter than a food. Thus, in the case of the citron, the bitter pips were thought to be particularly useful as drugs. However, there were various exceptions to the ‘bitter’ rule. Breast milk, for instance, is very sweet to the taste. It became a drug when it was administered to people who do not usually consume it (adults), or when it was applied externally (in particular, on the eyes) instead of internally. Today, the boundary between food and medicine remains relatively blurred.