Green, sprouts and damaged potatoes contain glycoalkaloids, those are toxic to humans when consumed in large quantities. It’s not a myth.
Actually, potatoes belong to nightshade family. All members of this family naturally produce natural pesticides, glycoalkaloids as a defence mechanism against insects, disease, and herbivores. Potatoes produce the two main toxic glycoalkaloids, α-solanine and α-chaconine which together account for 95% of the total glycoalkaloids content. These toxic glycoalkaloids found in all parts of a potato plant. Generally, potato leaves, stems, and shoots are naturally high in glycoalkaloids while the lowest is in potato tubers.
Actually, potatoes belong to nightshade family. All members of this family naturally produce natural pesticides, glycoalkaloids as a defence mechanism against insects, disease, and herbivores. Potatoes produce the two main toxic glycoalkaloids, α-solanine and α-chaconine which together account for 95% of the total glycoalkaloids content. These toxic glycoalkaloids found in all parts of a potato plant. Generally, potato leaves, stems, and shoots are naturally high in glycoalkaloids while the lowest is in potato tubers.
Glycoalkaloids concentration in different parts potato plants
Change in glycoalkaloids during potatoes storage…
When potato tubers are stored in the presence of light, they turn green and increase glycoalkaloids. The greenish is actually chlorophyll, but it is also an indication for an increase in the level of glycoalkaloid. Damaged tubers also contain elevated levels of glycoalkaloids.
What is the toxic dose?
The toxic dose is approximated at 2-5 mg/kg body weight while the lethal dose is estimated at 3-6 mg/kg body weight. According to U.S. FDA the maximum acceptable glycoalkaloid content is 20–25 mg/100 g fresh potato weight.
Signs and Symptoms of Potato Poisoning
Solanine poisoning is primarily displayed by gastrointestinal and neurological disorders. Symptoms include nausea, vomiting, fever, diarrhea, severe stomach upset and pain, burning of the throat, headache, drowsiness, restlessness, shaking, confusion, weakness, disturbed vision, thyroid problems, inflammation and pain in the joints.
Reported Cases of Solanine Poisoning
The below are some of the reported cases of human poisonings due to the ingestion of greened or damaged potatoes.
1. In 1970, the Lenape potato variety was removed from the market in Canada and USA as it contained high levels of glycoalkaloids (16–35mg/100g of fresh potato).
2. In Sweden, a conditional sales ban had to be imposed on Magnum Bonum potato variety in 1986, as it contained high levels of glycoalkaloids.
3, In an English school in 1978, solanine poisoning affected 78 schoolboys in Britain, but no one died. In this case potatoes found to contain high levels of solanine.
4. In 1983, 61 of 109 school children and staff in Alberta, Canada, fell ill after eating baked potato. (more potato poisoning cases, ref. 6 and 8).
The fatal cases of solanine poisoning are very rare these days.
Prevention of poisoning
In potatoes, skin, comprising 2-3% of the tuber, contains 30–80% of the glycoalkaloids. So peeling of potatoes will greatly reduce the levels of glycoalkaloids present. The glycoalkaloid content cannot be significantly changed by any form of cooking (i.e. baking, frying, and microwaving).
Some other advises...
-Store potatoes properly (i.e. in a cool, dry, dark place)
-Avoid the need for long-term storage.
-Peel the potatoes before cooking
-Remove the parts of the tuber that show damage, rotting, green colouring and sprouting before cooking
-Do not eat potatoes that taste bitter
References:
1. Potato here
2. Toxic glycoalkaloids in potatoes here
3. A review of occurrence of glycoalkaloids in potato and potato products, Omayio et. al., Curr. Res. Nutr. Food Sci. 2016;4(3)
4. Health canada's maximum levels for chemical contaminants in foods here
5. FDA poisonous plant database here
6. Solanine and chaconine here
7. Solanine here
8. Horrific tales of potatoes that caused mass sickness and even death here
Depending on variety and storage conditions, concentrations of glycoalkaloids in potato tubers vary. Poisonous symptoms may also vary depending on the ratio of body weight of the toxin and the individual’s tolerance of the alkaloid.
This article is just for information and education purpose only.
Depending on variety and storage conditions, concentrations of glycoalkaloids in potato tubers vary. Poisonous symptoms may also vary depending on the ratio of body weight of the toxin and the individual’s tolerance of the alkaloid.
This article is just for information and education purpose only.
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