Potatoes have a long history of being seen as poisonous. According to the Smithsonian, a green potato indicates the presence of a nerve toxin that can induce coma or even kill you within 24 hours of consumption. But, even scarier: Potato lectin is a poisonous glycoprotein that contains about 47% l-arabinose, 3% d-galactose and 11% hydroxyproline.