This is a common misconception, both for and against the argument. The main point is that you cannot generalize a statement such as this. A drug is, by definition, any substance, either synthetic or natural, that is taken for other than dietary needs. In this way, every single substance that enters the body and is not food is a drug. To many people in the public, "drug" simple means "a recreational illicit substance". This is misleading, because the caffeine in coffee and alcohol are both drugs.

    The second statement, about chemicals, is even more misleading. The public commonly thinks of chemicals as dangerous, synthetic, substances that harm your body. By definition, a chemical is any substance that has a definite composition. This means that every single carbohydrate in the food we eat, and every single protein in our muscle cells, and every single molecule of water we drink, are all chemicals. In fact, every single thing in the world is made of different chemicals. Some are deadly, other's are harmless, and some are vital to our survival.

Sources:

1. "Chemicals, Lesson 1, Glossary", National Institute of Heath, http://science.education.nih.gov/supplements/nih2/chemicals/other/glossary/glossary1.htm

2. "Glossary", Thinkquest, http://library.thinkquest.org/C007974/glossary.htm