Glycoalkaloids are naturally occurring substances within the potato tuber that can cause the vegetable to have a coppery taste. The most common glycoalkaloid that is found in potatoes is solanine, which, when ingested in large amounts, can cause toxic reactions in the human system. Solanine is present in the potato and other vegetables in the nightshade family because it acts as a fungicide and pesticide.
The symptoms of a toxic reaction to solanine are primarily neurological and gastrointestinal in nature. Oftentimes, the first symptom of mild solanine poisoning is stomach upset and nausea. Reactions to solanine are most often not dangerous, as the body processes the toxin effectively. Sometimes, in susceptible individuals, vomiting and burning of the throat can occur after the initial gastrointestinal symptoms. Neurologic symptoms include headache, dizziness and hallucinations. Death has been reported when solanine is ingested in very large quantities.
Effects on the Body
The method by which solanine takes action upon the human body is not fully understood. It is thought to be caused mainly by its interaction with the membranes of the mitochondria within the cell. The solanine may cause the opening of the potassium channel, which increases the electrical activity within the cell. Increased electrical activity is thought to be the cause of the majority of symptoms that are experienced when coppery-tasting potatoes are eaten.
Causes of Solanine Production
When potatoes are exposed to bright light, they begin to turn green, which is the first visual sign of solanine production. The plant produces the substance so that it becomes less edible to animals that are foraging for food in the daylight hours. The green color is merely a symptom that solanine is being produced, however, as the hue is caused by an increase in chlorophyll, which is safe for human ingestion.
Preventing Solanine Production
The coppery taste, and in turn, solanine production, can be prevented in various ways. While it is safe to eat a potato that has some green hue, the affected parts should be cut off before consumption. Sprouted potatoes that have numerous eyes are also known to be high in toxins and should be avoided if possible. If a potato appears sunburned, it should be discarded as well.