Potato peril: Hidden dangers of solanine in your favorite vegetable

The potato originates from present-day Chile. It was first cultivated by the Incas, who created fields and irrigation systems on the slopes of the Andes.

Today, the potato is one of the most important crops in our climate zone. It is available in over a thousand varieties differing in the size and shape of tubers and the skin or flesh colour – from light to red and even bluish-purple.

Potatoes are a rich source of starch, easily digestible proteins, and vitamins, especially C (which strengthens the immune system and protects against the harmful activity of free radicals) and B vitamins, essential for the proper functioning of, among others, the nervous system. They contain a lot of potassium and magnesium.

Despite valuable nutrients, potatoes also hide compounds that, although they protect the plant from pest attacks and diseases, are poisonous to humans. These include steroidal glycoalkaloids, especially solanine. What is worth knowing about it?

Glycoalkaloids, produced in various parts of the plant (flowers, leaves, sprouts, tubers), develop primarily when the potato is exposed to sunlight. They also thrive when potatoes are stored at temperatures above 10°C and packaged in materials that protect against light or chemical agents. Visible signs of solanine expansion include green spots and young shoots on the tubers.

Due to the high consumption of potatoes, their glycoalkaloids are one of the most common sources of toxic substances in the human diet. The consequences of poisoning, usually 7-19 hours after a meal, can include typical stomach problems: nausea, vomiting, stomach aches and headaches, colic, diarrhoea, excessive sweating, and fever. Occasionally, there may also be consciousness disorders, breathing problems, heart arrhythmia, and even hallucinations.

When the concentration of solanine in the blood remains high for a long time, symptoms such as tachycardia (very fast heartbeat), neck stiffness, partial paralysis, or coma can occur. In the case of severe poisoning, hospitalisation may be necessary.

The dangerous compound causes changes in the functioning of many important organs and the nervous system. Even if it initially does not cause serious ailments, it accumulates in the liver, kidneys, and heart, leading to gradual degeneration. Solanine irritates the mucous membrane of the mouth, oesophagus, and stomach and causes liver, kidney, or gallbladder inflammation.

The harmful dose of solanine is 2-5 mg/kg of body weight. Under normal conditions, it is hard to exceed – a person weighing 9 stone would need to consume over 1 kg of potatoes daily to ingest a dangerous amount of glycoalkaloid. However, considering the rapid increase of this compound in sunlit tubers, this value decreases to as little as 500 grams of potatoes.

According to some studies, the concentration of glycoalkaloids decreases significantly when potatoes are peeled while cutting, while most processing methods, such as boiling, baking, frying, or drying, do not significantly affect the content of these compounds since they break down only at temperatures above 250°C.

Advice? Avoid buying potatoes with green spots or sprouts—store potatoes in cool and dark places without access to sunlight. If you observe disturbing changes on the tubers, carefully cut them out, as most solanine accumulates just under the skin.

It is worth knowing that glycoalkaloids are not only found in potatoes. A rich source of solanine can also be carrots, especially the part of their root that protrudes above the ground, usually right next to the greens, as indicated by the characteristic greening. Therefore, before cooking, it should simply be cut off.

The dangerous compound is hidden in aubergines. This vegetable, popular in Mediterranean cuisine, is becoming increasingly popular in the UK. At the same time, it is also a treasure trove of solanine, so aubergines should not be eaten raw. It is worth peeling and salting them before preparing, which reduces the concentration of glycoalkaloids.

Such compounds are also rich in green tomatoes, especially in tomatoes. It is advisable to avoid eating them raw, especially in larger quantities. Like solanine, tomatine is not neutralised by thermal processing, but fried, boiled, or pickled green tomatoes are much healthier. However, children under the age of 10 and people with hypertension should avoid eating them. A better choice for them would be ripe red tomatoes.