It can occur naturally in any part of the plant, including the leaves, fruit, and tubers. Solanine has fungicidal and pesticidal properties, and it is one of the plant’s natural defenses.
Symptoms of Solanine Poisoning
Solanine poisoning is primarily displayed by gastrointestinal and neurological disorders. Symptoms include nausea, diarrhea, vomiting, stomach cramps, burning of the throat, cardiac dysrhythmia, nightmare, headache and dizziness. In more severe cases, hallucinations, loss of sensation, paralysis, fever, jaundice, dilated pupils, hypothermia and death have been reported.
In large quantities, solanine poisoning can cause death. One study suggests that doses of 2 to 5 mg per kilogram of body weight can cause toxic symptoms, and doses of 3 to 6 mg per kilogram of body weight can be fatal.
Symptoms usually occur 8 to 12 hours after ingestion, but may occur as rapidly as 30 minutes after eating high-solanine foods.
The lowest dose to cause symptoms of nausea is about 25 mg solanine for adults, a life-threatening dose for a regular-weight adult ranges about 400 mg solanine.
Solanine in Potatoes
Solanine occurs naturally in many species of the genus Solanum, including the potato (Solanum tuberosum), tomato (Solanum lycopersicum), eggplant (Solanum melongena), and bittersweet nightshade (Solanum dulcamara).
Potatoes naturally produce solanine and chaconine, a related glycoalkaloid, as a defense mechanism against insects, disease, and predators. Potato leaves, stems and shoots are naturally high in glycoalkaloids.
When potato tubers are exposed to light, they turn green and increase glycoalkaloid production. This is a natural defense to help prevent the uncovered tuber from being eaten. The green colour is from chlorophyll, and is itself harmless. However, it is an indication that increased level of solanine and chaconine may be present.
Some diseases, such as late blight, can dramatically increase the levels of glycoalkaloids present in potatoes. Mechanically damaged potatoes also produce increased levels of glycoalkaloids. This is believed to be a natural reaction of the plant in response to disease and damage.
In potato tubers, 30–80% of the solanine develops in and close to the skin.
In the 70s, Solanine poisoning affected 78 school boys in Britain. Due to immediate and effective treatments, no one died.
Showing green under the skin strongly suggests solanine build-up in potatoes, although each process can occur without the other. A bitter taste in a potato is another, potentially more reliable indicator of toxicity. Because of the bitter taste and appearance of such potatoes, solanine poisoning is rare outside conditions of food shortage. The symptoms are mainly vomiting and diarrhea, and the condition may be misdiagnosed as gastroenteritis. Most potato poisoning victims recover fully, although fatalities are known, especially when victims are undernourished or do not receive suitable treatment. Fatalities are also known from solanine poisoning from other plants in the nightshade family, such as the berries of Solanum dulcamara (woody nightshade).
The United States National Institutes of Health’s information on solanine says to never eat potatoes that are green below the skin.
Deep frying potatoes at 170°C (338°F) is known to effectively lower glycoalkaloid levels (because they move into the frying fat), as does boiling (because solanine is water soluble), while microwaving is only somewhat effective, and freeze drying or dehydration has little effect.
Potato Plant Poisoning – Green Tubers and Sprouts
Potato plant poisoning occurs when someone eats the green tubers or new sprouts of the potato plant.
This is for information only and not for use in the treatment or management of an actual poison exposure. If you have an exposure, you should call your local emergency number (such as 000) or the Australian Poisons Information Centre at 13 11 36.
Solanine (very toxic even in small amounts)
The poison is found throughout the plant, but especially in green potatoes and new sprouts. Never eat potatoes that are spoiled or green below the skin. Always throw away the sprouts.
Potatoes that are not green and have had any sprouts removed are safe to eat.
Do not touch or eat any plant with which you are not familiar. Wash your hands after working in the garden or walking in the woods.
Seek immediate medical help. Do NOT make a person throw up unless told to do so by the poison centre or a health care professional.
Before Calling Emergency
Determine the following information:
- Patient’s age, weight, and condition
- Time it was swallowed
- Amount swallowed
- Name and part of plant that was swallowed
The National Poisons Information Centre (13 11 36) can be called from anywhere in Australia. This national hotline number will let you talk to experts in poisoning. They will give you further instructions.
What to Expect at the Emergency Room
The health care provider will measure and monitor your vital signs, including temperature, pulse, breathing rate, and blood pressure. Symptoms will be treated as appropriate. You may receive:
- Activated charcoal
- Blood and urine tests
- Breathing support
- Chest x-ray
- EKG (electrocardiogram, or heart tracing)
- Fluids through a vein (IV)
- Medication to treat symptoms
- Tube through the mouth into the stomach to wash out the stomach (gastric lavage)
- How well you do depends on the amount of poison swallowed and how quickly treatment is received. The faster you get medical help, the better the chance for recovery.
- Symptoms may last for 1-3 days, and hospitalisation may be necessary.
- Death has been reported, but is rare.
Do not touch or eat any plant with which you are not familiar. Wash your hands after working in the garden.