Beware of Eating Green Potatoes

A recent article in the New York Times provides an important dietary warning:

Green potatoes often contain high levels of a toxin called solanine, which can cause any of the following gastrointestinal and/or neurological symptoms upon ingestion:

• Nausea
• Vomiting
• Stomach cramps
• Diarrhea
• Burning sensation in throat region
• Headaches
• Dizziness
• Hallucinations

If ingested in large quantities (3 to 6 mg per kilogram of body weight), solanine can even cause death.

Symptoms of solanine poisoning tend to occur about 6 to 12 hours after ingestion, but can also occur within several minutes when foods that are highly concentrated in solanine are ingested.

Solanine is a chemical that is produced in small amounts by potatoes as a natural defense mechanism against insects. Prolonged exposure to warm temperatures and light can increase solanine content in potatoes.

The green tint that potatoes can take on is caused by high chlorophyll content; potatoes produce chlorophyll and solanine at the same time, so a high level of chlorophyll often accompanies high solanine content. Chlorophyll by itself is not harmful to human health.

Alexander Pavlista, a professor of agronomy and horticulture at the University of Nebraska, Lincoln, reports that a 100-pound person can experience illness after eating just 16 ounces (1 pound) of a fully green potato - this is about the average weight of a large, baked potato.

Commercial varieties of potatoes are screened for solanine. But if left for too long and/or stored improperly, potatoes can build up their solanine content to dangerous levels.

In order to prevent unnecessary formation of and exposure to solanine, it is best to store potatoes in cool, dark areas, and to trim away green areas before preparing them to eat.

Occasionally, a potato that is not green can also be high in solanine content. High solanine levels usually result in bitter potatoes, so don't continue eating a potato that is bitter upon first bite.

Solanine is also produced naturally by chili peppers, bell peppers, tomatoes, eggplant, and tobacco. But the average intake of solanine from these plants is not usually significant; most ingested solanine comes from potatoes.