Updated on 4/4/2005
The chemical in question is solanine, a toxin that forms in the sprouts and green parts of potatoes. You can avoid it by cutting away sprouts ("eyes") from potatoes and peeling them below any green layer. And don't eat any potatoes that taste bitter; the flavor might indicate the presence of solanine.
Solanine is a significant toxin, but you are unlikely to run into trouble with it in our part of the world, because we grow potato varieties that do not produce much of it. That is not the case in Peru, where potatoes originated, and some older varieties can contain high amounts. A 200-pound person would have to eat two pounds of fully green potatoes in a single day to consume a toxic level of solanine. Symptoms include abdominal pain, nausea, diarrhea, vomiting, drowsiness, mental confusion, shortness of breath, weak and rapid pulse, and, eventually, respiratory failure.
There hasn't been a single case of solanine poisoning due to eating potatoes in the United States for more than 50 years.
To avoid the "greening" process that can lead to solanine formation, don't buy green potatoes and call any potatoes with green coloration to the attention of the produce manager at your market. At home, follow these guidelines:
- Store potatoes in a dark, cool place, such as in a basement.
- Wash potatoes before cooking and check carefully for green areas.
- Peel potatoes deeply enough to remove any green tissue present.
Andrew Weil, M.D.