Will Eating Green Potatoes Make You Sick?

Potatoes keep well when stored in proper conditions. Potatoes stored improperly, either in the store or at home, can develop a green cast or patches. Most of this greening happens either to the skin of the potato or to the layer just beneath the skin. Eating the green parts of these potatoes can make you sick.

Causes

Potatoes green when exposed to light. In the field, potatoes can work their way to the surface and be exposed to light there. In transport, at the store or in the home, exposure to either sunlight or florescent lights can cause greening. When exposed to light, potatoes form chlorophyll. Forming chlorophyll is the first stage in the sprouting process. If you watch an organic green potato, within a few days, little green and white sprouts will poke out of the potato at the eyes.

Toxins

The chlorophyll in green potatoes is not in itself harmful. Chlorophyll is, however, a visible sign of an invisible process going on in the potato at the same time as greening. Exposure to light also produces solanine, an alkaloid that is toxic. It is possible to find solanine in a potato that isn't green, and it is possible to have some greening without solanine being present. The two, however, are so commonly found together that greening is considered to be a marker for the presence of solanine.

Health Effects

According to Maria Cantwell of the Postharvest Technology Center at the University of California Davis, potato alkaloids like solanine interfere with the body's ability to regulate acetylcholine. Acetylcholine regulates nerve impulses. Consequently, if you eat small to moderate amounts of solanine, you can experience stomach cramps and diarrhea. If you eat large amounts of solanine, your heart rate and respiration rate will increase. At the highest doses, you may experience hallucinations, shock, coma or even death. If potatoes are quite green, 2 pounds of them would make a 200-pound person severely ill. Similarly, one pound would make a 100-pound person sick, and a mere 1/2 pound would make a 50-pound person sick.

Prevention

To avoid solanine poisoning, avoid green potatoes. Don't buy potatoes that are green. Store potatoes in a cool, dark place. Don't store them on the kitchen counter. If a potato has greened in a few spots, cut away the green parts and take a thick peel. Solanine tends to form within 1/8 inch of the skin. Don't eat the peels of a potato if it is greening, sprouting or old. Cut away the potato eyes and never eat potato sprouts. Sprouts contain the highest concentration of solanine.