Potatoes are far and away the most commonly eaten vegetable by Americans. These delicious tubers however, have on occasion been known to kill humans. According to Smithsonian Magazine, potatoes contain a nerve toxin called solanine which in high concentrations can cause vomiting, coma, twitching and even death.

If a potato is green or turning green chlorophyll is present which isn’t harmful – it does however indicate that there is a concentration of some level of solanine. These days poisoning is rare as most commercial potatoes are screened for it.

The nerve toxin is produced in the green part of the potato (the leaves, the stem, and any green spots on the skin). The reason it exists? It’s a part of the plant’s defense against insects, disease and other predators.

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If stored incorrectly, potatoes can build up levels of the toxin. The article recommends:

The best way to prevent solanine poisoning is to store tubers in a cool, dark place and remove the skin before consumption. A general rule for avoiding illnesses like the ones described above? Green and sprouted? Throw it out.