The green sign: It waits in the bag in the pantry, goes into mashed potatoes, fries, soup, and the oven – but a potato that has turned greenish or sprouted is not just less aesthetic. The green color itself comes from chlorophyll and is not the poison, but it serves as a warning sign that storage conditions encouraged the accumulation of natural substances that the plant produces as a defense.
These substances are called glycoalkaloids, and the most familiar of them is solanine. They are usually found in the potato in small quantities, mainly in the skin and adjacent areas. When the tuber is exposed to light, heat, mechanical damage, or prolonged storage, the amount can increase. Therefore, a green, bitter, very soft, or sprout–filled potato should raise a red flag.
The problem with solanine is that it does not disappear easily in regular home cooking. Frying, baking, or boiling do not guarantee full decomposition of the toxin. Deep peeling and removing green areas can reduce exposure when the damage is small and localized, but if the potato is significantly green or bitter – it is better to simply throw it away.
Solanine poisoning is not common, but it is documented. The first symptoms are usually in the digestive system: Nausea, vomiting, abdominal pain, diarrhea, and a burning sensation in the mouth or throat. In more severe cases, headaches, dizziness, confusion, weakness, a drop in blood pressure, and neurological disorders may appear. Young children, the elderly, and people with underlying medical conditions may be more sensitive.
It is important to say this carefully: A regular potato, kept properly and looking normal, is not dangerous. It is a source of carbohydrates, potassium, vitamin C, and fiber, especially when it is eaten with the skin in a normal condition. The story is not against potatoes, but against ignoring clear warning signs.
One of the common mistakes is to think that "if we cook well, everything will be fine." This is true for many bacteria, but not for every natural toxin. Glycoalkaloids are relatively heat–resistant, and therefore cooking is not an insurance policy. A bitter taste is also an important sign: If the potato is unusually bitter, do not continue to eat it and do not give it to children.
The best way to avoid the problem is proper storage. Potatoes should be kept in a cool, dark, dry, and ventilated place. Not near a window, not in the sun, and not in a closed, damp bag. A refrigerator is not always the preferred choice, because storage that is too cold may change the sugar composition and affect the taste and browning, but light and heat are the biggest enemies.
Smart buying is also important. At the supermarket or the market, it is advisable to choose firm potatoes, without green spots, without multiple sprouts, and without an unusual smell. At home, if an old bag started to sprout there is no need to panic, but every tuber must be checked individually. A small sprout on a firm potato without greenishness is not a sign for concern and it can be removed (along with a bit more of the potato itself), but a green or bitter vegetable does not justify the risk.
The message is simple: A potato is a safe and useful food when it looks and behaves like a normal potato. When it changes color, grows many sprouts, or gets a bitter taste, it is already telling a different story. In the kitchen, sometimes the small sign on the skin is the difference between a routine dinner and unnecessary stomach aches.
Dr. Itay Gal is a specialist in pediatrics, sports and aviation medicine, and the medical commentator for Maariv. For more articles click here