Q: My grandmother was told that eating vegetable members of the nightshade family would exacerbate her arthritis. Which ones should she avoid? Why are they called nightshade?

A: The nightshade (solanum) family is very diverse, covering tobacco, jimson weed, angel trumpet and belladonna. It also includes tomato, eggplant, pepper, and Irish potato. There are many chemicals in nightshade plants. A few of them are poisonous and some medical professionals believe the other chemicals can affect specific human diseases in small doses. Belladonna is known as deadly nightshade. Though belladonna means “beautiful woman” and solanum might refer to the sun, I can find nothing that explains why this family is called nightshade.