Green potatoes

When they’ve been sitting around for a while, exposed to light and warm temperatures, potatoes can start to produce a chemical called solanine that, in high enough concentrations, can cause nausea, headaches and neurological problems, according to the New York Times. Conveniently, though, you can tell it’s happening because the potatoes turn green – they produce chlorophyll at the same time they’re making solanine. If you see green spots, cut them off your potatoes before cooking.
Fugu

Fugu, aka pufferfish, are the second-most poisonous vertebrate in the world (after the golden poison frog), but their meat is sold for hundreds of dollars at high-end restaurants in Japan, reports CNN. Chefs are required to train for three years before passing a test to be sure they’re qualified to prepare the delicacy, but it still causes numerous cases of food poisoning every year, mostly among fishermen who prepare the fish at home, according to the BBC.
Pufferfish may not be on the menu, but you may be planning other types of fish for dinner. Before you get started, discover 9 ways you’ve been cooking fish completely wrong.
Raw elderberries

These berries make delicious jams, compotes, syrups and pies, but only after they’re cooked. Raw berries (and the plant’s bark and leaves) contain a compound that can cause nausea. Parts of the plant can also contain toxic substances – livestock have died after eating its roots and young leaves.