few days ago somebody commented that they could never go on a macro diet because the nightshade vegetables are forbidden. For those who don't know, nightshades come from the family Solanaceae and include tomatoes, peppers, eggplant and potatoes. These are for many of us some of our most popular vegetables. We certainly do not remember that there was a time when they were considered poisonous and only grown as ornamentals. All nightshade vegetables contain solanine, a nicotine compound.