Potatoes sometimes turn green, which may indicate high levels of a potentially toxic compound. People should take certain precautions with potatoes that are green under the skin.
In general, people should not eat green potatoes unless they take certain safety precautions, such as cutting away all the green parts of the vegetable that contain the poisonous compound, which is called solanine.
This article discusses whether or not is it safe to eat a green potato and shares symptoms of solanine poisoning. It also looks at the reasons a potato turns green and possible ways to prevent discoloration.
While the chlorophyll in green potatoes is not necessarily harmful, the color may indicate other processes have taken place inside the potato. The most significant of these is the formation of solanine, which is created after the vegetable is exposed to light. Solanine is also present in the sprouts, roots, and leaves of a potato. The substance is a neurotoxin. If a person eats solanine it can cause headaches and nausea.
Solanine is naturally present in all potatoes, generally in the upper one-eighth of the skin. It is a colorless alkaloid with a bitter taste. Usually, a person will not keep eating a bitter potato because of the taste. However, if they were to eat a large amount of green potato they might get solanine poisoning. When solanine levels in a potato are greater than 0.1% the vegetable is not suitable for eating and could make a person sick.
The normal amount of solanine in a potato’s peel means a 200-pound person would have to eat 20 pounds of potatoes to experience a toxic level, according to the University of Nebraska. However, exposure to light can increase solanine levels up to 10 times. This makes even 2 pounds of potatoes potentially dangerous, as a large baked potato can weigh about 1 pound. Most potato servings in a restaurant are about 6 to 8 ounces.
Solanine poisoning symptoms include:
- pain in the stomach or abdomen
- body temperature lower than normal
- slow pulse
- slow breathing
A person should seek immediate medical advice if they believe they have any symptoms of solanine poisoning from eating green potatoes.
Many potato varieties are grown worldwide, although the plant was originally native to South America and is related to tomatoes and tobacco. The part of the potato plant (Solanum tuberosum) that is generally eaten is called a tuber, and they grow underground on the roots of the plant.
Under the skin, a potato is generally a white color. However, if the potatoes are exposed to light, they will produce chlorophyll, which will give them a green color, and may also develop high levels of solanine.
Some potato varieties are more likely to turn green than others. This includes white-skinned potatoes versus russet potatoes or other red-skinned varieties. Also, the place where potatoes are grown – such as on top of a hill – may make them more likely to turn green.
A person should never eat a potato that is extensively green.
Cooking a green potato does not render it safe. If the green portion of the potato is only on the top of the skin or in a small area, a person can usually cut out that portion and safely eat the remainder. However, if the potato tastes bitter, a person should not continue to eat it. Generally, if there is extensive green color throughout a potato, it is not possible to cut away enough of the solanine material to make it safe to eat.
Because sunlight causes potatoes to turn green, keeping them away from the sun can prevent them from turning green. The U.S. Department of Agriculture’s FoodKeeper website and app provide advice on how to store potatoes and other foods.
Recommended storage methods include:
- in a cellar or basement, where temperatures are usually cooler and dark
- at a temperature between 45 to 50 degrees Fahrenheit
- away from any appliance that gives off heat, such as a refrigerator
A person growing potatoes should keep soil around a potato plant, known as “hilling,” to ensure its tubers do not come in contact with light. Allowing potatoes to grow too close to the soil’s surface can cause them to become green.
Potatoes with extensive green coloring may be potentially toxic, and there is no method of making them safe to eat.
Someone who does not want to waste a green potato could plant it in the ground or in a pot. If allowed to sprout it will eventually produce new potatoes.