some nutrients are drugs like lithium, i would classify that as a drug and a potent one at that. There are many more examples like this and to remove things because they have nutritional properties further complicates the matter.
The semantics of the word "drug" is imprecise and nebulous, thus allowing the concept to be expanded to encompass pretty much everything. But a word that describes everything has no meaning, because words are terms of description of aspects of reality and not of all of it. Because of this the word drug is used to describe substances, other than food and water, that affect your physiology. Caffeine is not needed to sustain life and affects your physiology, thus being best described as a drug and not a food.
Lithium is included in the food category because it is needed in the diet and I defined drugs as substances other than food and water that affects your physiology, just like Mercury which is also found in certain foods and affects your physiology but is not needed. Besides, using your definition it means nothing, because sugar also affects your mood causing drowsiness by raising serotonin levels,. Should we classify sugar as a drug? What about Magnesium? It makes your sleepy, and is a nutrient. Should we call it a drug too? If we are going to drug as anything that affects your physiology, then we should abolish the word food as it becomes redundant since all foods by definition affect your physiology. We should also abolish the words "Oxygen" and "ulteraviolet rays" since they also affect your physiology and could just be called drugs. A drug is a
substance, other than
food and water, which
affects your physiology. The terms in bold qualify the precision of the definition.
SUCKMYMUSCLE