It makes no sense to talk about the effects of certain substances on the body without talking about amounts. Licking an aspirin tablet will do nothing for a headache, but swallowing two tablets will make the headache go away. Swallowing a whole bottle of pills will make the patient go away. Chemicals are the building blocks of our world. They are neither good nor bad.
Nitroglycerin can alleviate the pain of angina or blow up a building.
The choice is ours. Furthermore, there is no relation between the risk posed by a substance and the complexity of its name. Nature is not benign. The deadliest toxins known, such as ricin from castor beans or botulin from the Clostridium botulinum bacterium, are perfectly natural. The properties of any substance are determined by its molecular structure, not by whether it was synthesized by a chemist in a lab or by nature in a plant.