The leaves and stems of both tomatoes and potatoes, members of the nightshade family, contain a toxic alkaloid called solanine. In potatoes, it is particularly concentrated when the spud starts to sprout and when the eyes and flesh turn green.
Prior to 1820, Americans considered tomatoes to be poisonous, but the chance of suffering symptoms of solanine toxicity from tomatoes isn’t that likely. Potatoes have higher concentrations – and a report form the University of New Mexico notes that wild potatoes in the Andes can be more than double that of cultivated potatoes. But even so, a 100-pound person would need to eat 16 ounces of a fully green potato before solanine poisoning would occur. If you happen to have a taste for green potatoes, keep an eye out for excessive salivation, diarrhea, slowed pulse, reduced blood pressure and respirations, and cardiac arrest.