How toxic is the solanine on potatoes?

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• 1 Jonsoeser // Oct 12, 2008

  It is very toxic even in small quantities. Solanine has both fungicidal and pesticidal properties, and it is one of the plant’s natural defenses.

  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.

  Commercial varieties of potatoes are screened for solanine levels[in which countries?], and most have a solanine content of less than 0.2 mg/g. However, potatoes that have been exposed to light and started to green can show concentrations of 1 mg/g or more. In these situations a single unpeeled potato can result in a dangerous dose.

  In potato tubers 30–80% of the solanine develops in and close to the skin.

  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.[1] Fatalities are also known from solanine poisoning from other plants in the nightshade family, such as the berries of Solanum dulcamara (woody nightshade).[2]

  The National Institute of Health’s information on solanine says to never eat potatoes that are green below the skin.

  Deep-frying potatoes at 170°C (306°F) is known to effectively lower glycoalkaloid levels, whereas microwaving is only somewhat effective and boiling has no effect.