by Carol Dunn

Created on: December 25, 2011

Potatoes can turn green if bruised, damaged by insects, exposed to sunlight or very cold temperatures, or if they begin to sprout.  The greenish tint is a sign that solanine is present in the potato, and it should not be eaten. 

Solanine, a glycoalkaloid common to the nightshade family (ie. potatoes, tomatoes, eggplants, peppers), is a nerve toxin present in the leaves and stems of the potato plant.  These parts of the plant are never to be eaten, and if there are green spots on the peel, some sources advise that you discard the entire potato. 

Solanine, concentrated just below the potato peel, is a poison that is a natural defense against fungi, viruses, insects and other predators.  The Food Safety Watch web site (www.foodsafetywatch.com) reports, “. . . even in commercially available tubers destined for human consumption, a residual level of these compounds is always present.”  

Throughout history, small amounts of solanine have not typically been dangerous to humans, but it is best to avoid consuming it if you can.  It interferes with normal cell activity and nerve impulses and, if enough is eaten, will make animals and people sick.  Symptoms can include a bitter taste, a burning irritation in the mouth and on the side of the tongue, headaches, fatigue, nausea, vomiting, diarrhea, circulatory and respiratory problems, and stomach and abdominal cramps.  Children are particularly at risk for solanine poisoning because of their smaller body size. 

According to www.Snopes.com , a person would have to consume over four pounds of green potatoes to suffer neurological problems.  However, according to the Health Canada web site, www.hc-sc.gc.ca , there have been reports of deaths caused by eating potato leaves, sprouts, berries and green skinned tubers.  Food Safety Watch reports two of these deaths in 1925, one in 1933, and 22 between 1952-1953.  Anecdotal stories found on gardening blogs indicate that eating as little as a cup of potatoes with green skins can result in severe gastrointestinal distress.  Others report no ill effects from eating potatoes that had green spots on the skins.    

Some recommendations for reducing your exposure to solanine from potatoes include: storing potatoes at cool temperatures in the dark, cutting away cut or bruised portions, and removing the eyes and peels before cooking.  If potatoes taste bitter or cause a burning sensation in the mouth, discard them. 

If you are growing your own potatoes, make sure the ground is mounded around the base of the plant, so no sunshine reaches any of the tubers as they grow.    

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