Green potatoes are harmful and can cause food poisoning when eaten. The green color signifies the presence of the toxin solanine, which can cause headaches, nausea and neurological problems, reports “The New York Times.” A 100-pound person would have to eat 16 oz. of a fully green potato -- about the size of a large baked potato -- to get sick, reports “The New York Times,” but most people don’t get that far because of the bitter flavor that accompanies the toxin.
The Poisonous Substance
The toxin in green potatoes is a glycoalkaloid and helps protect the potato from insect and fungal attack. Solanine is found throughout the potato plant, reports MedlinePlus, but is concentrated in green potatoes and the new sprouts or “eyes.”
Exposure to light causes the potato to produce chlorophyll and the green patches act the way leaves do, explains CSIRO. This also triggers the production of glycoalkaloids to protect the new growth. Solanine is also produced in response to damage: bruises, cuts and rotting. Potatoes turn green when they grow too closely to the soil surface or when they’re stored in warm temperatures or under light, according to Purdue University.
Solanine poisoning occurs eight to 12 hours after eating green potatoes, according to Science Daily. Diagnosis can easily be confused with other causes because of the wide range of symptoms. MedlinePlus lists abdominal or stomach pain, diarrhea and vomiting as a few of the symptoms. Headache, fever, low body temperature and slowed breathing and pulse can also occur from eating green potatoes. Dilated pupils and vision changes, loss of sensation or paralysis are more serious symptoms, as well as delirium, hallucinations and shock.
Human and livestock deaths have been reported from eating green potatoes in rare cases. Pregnant women should avoid eating green potatoes as the glycoalkaloids may be harmful to the fetus or cause miscarriage, reports CSIRO.
Thick-skinned, older potatoes are less likely to turn green than young, thin-skinned potatoes, according to CSIRO. Take care when buying red-skinned potatoes as greening is harder to detect. Eat thin-skinned potatoes promptly and store older potatoes in a cool, dark and dry place. Cooking does not destroy solanine but it is possible to cut away the green areas and sprouts to eliminate most of the glycoalkaloids.
- The Commonwealth Scientific and Industrial Research Organisation: Greening of Potatoes
- Science Daily; ‘Green’ Potato Health Risk Can Be Eliminated By Cutting Away Affected Area; July 28, 2008
- "The New York Times"; The Claim: Green Potatoes Are Poisonous; Anahad O’Connor; July 3, 2007
- MedlinePlus: Potato plant poisoning - green tubers and sprouts
- Purdue University: Potatoes Turning Green; B. Rosie Lerner