This versatile tuber, also known as manioc and yuca, is a staple throughout much of its native South America and in parts of Africa and Asia. (It is also the source of tapioca.) There are two main varieties, sweet and bitter, but both contain a cyanogenic glucoside called linamarin, which decomposes into poisonous hydrogen cyanide. In sweet cassava, the poison is concentrated near the surface and peeling and cooking removes all traces of it. It’s laced throughout bitter cassava, however, and that tuber must be grated, thoroughly washed, and pressed before cooking to remove it. Needless to say, neither kind can be eaten raw.
Eggplant is a member of the nightshade family (one of its relatives is so-called deadly nightshade, also known as belladonna), and like other family members contains solanine, a bitter-tasting steroidal compound. Too much solanine can cause nausea, dizziness, and other health problems, and extremely high doses can be fatal. Cooking eggplant lessens its solanine content, however, and anyway most authorities agree that you’d have to eat unreasonable amounts of the vegetable to experience ill effects. Nonetheless, some people are allergic to even small quantities of the compound, so it’s safer not to sample eggplant raw.
3. Green beans
There are more than 130 varieties of green beans, and they are generally considered a very healthful vegetable, full of vitamins A, C, and K. Eating a few of them raw in a salad shouldn’t be a problem, but they’re mildly toxic unless cooked. They also contain lectins — so-called antinutrients that limit the body’s ability to absorb vitamins and minerals, and may cause digestive issues. Cooking reduces these to negligible amounts.
4. Kidney beans
There’s actually an illness called red kidney bean poisoning, characterized by extreme nausea, diarrhea, and abdominal pain. This is caused by a toxin called phytohaemagglutinin, present in high concentration in raw kidney beans. Heating them insufficiently, as in malfunctioning slow cookers, can actually increase their toxicity — but thorough cooking renders them harmless.
5. Lima beans
Like cassava, raw lima beans contain linamarin, which decomposes into cyanide. Limas sold commercially in the United States are required by law to have lower levels of the compound than those grown elsewhere, though, and thorough cooking neutralizes the poison. (The beans should be cooked uncovered to allow the linamarin to escape as vapor.)