1. Lima beans
Like many legumes, the seemingly innocent lima bean should not be eaten raw - doing so can be lethal. (And who wants to die in such an ignoble way as death by lima bean?) Also known as butter beans, the legumes can contain a high level of cyanide, which is part of the plant's defense mechanism. Here in the U.S. there are restrictions about cyanide levels in commercially grown lima bean varieties, but not so in less developed countries, and many people can get sick from eating them. Even so, lima beans should be cooked thoroughly, and uncovered to allow the poison to escape as gas. Also, drain the cooking water to be on the safe side.
Whoever ate the first pufferfish must have been adventurous. (And most likely died shortly thereafter.) Almost all pufferfish contain tetrodotoxin, a deadly toxin that is up to 1,200 times more poisonous than cyanide. The poison in one pufferfish is enough to wipe out 30 humans, and there's no known antidote.
Yet, many people eat it. Called fugu in Japan, the meat of the pufferfish is a highly prized dish that is prepared by specially trained, licensed chefs. Even so, according to government figures, there were 23 deaths among 338 fugu poisoning cases recorded in Japan from 2000 to 2009.
3. Castor beans
Many a granny came armed with a spoonful of castor oil to heal all ills, and studies show that it does indeed have health benefits to offer. Just be sure not to eat the beans from which the oil came. If castor beans are chewed and swallowed, they can release ricin, one of the most toxic poisons known to man. Eating just one or two castor beans can easily cause the demise of the eater. Ricin has been investigated as a warfare agent, and has even been employed by secret agents and assassins.
Any reader of old-school mystery novels knows what the smell of bitter almonds signifies: death by cyanide, my dear Watson. And that's because some plants, including apples and bitter almonds, have cyanide in them to discourage herbivores from devouring them.
But don't fret; bitter almonds aren't the same as sweet almonds, the ones we eat in the United States. Since about 20 bitter almonds are enough to kill an adult, they aren't sold here. That said, almond extract is made with the oil of bitter almonds, but rest assured, it can't be used as a murder weapon.
Also known as manioc or tapioca, bitter casava is native to South America and is the third most important source of calories in the tropics; and like bitter almonds, cassava also harbors cyanide. When properly soaked and dried, bitter cassava is okay; but when any of the process is skimped on, problems arise.
Due to correct food processing and strict regulations, cyanide-laced cassava poses little threat to Americans who eat the root. But, in Africa, where cassava has become a major part of subsistence diets, many poor people suffer from a chronic and crippling form of cyanide poisoning known as konzo. The Bill and Melinda Gates Foundation is helping in the efforts to breed cassavas with less cyanide, but success has not yet been achieved.
Rhubarb stalks may lend a super tart tang to strawberry pie; but their leaves offer something altogether different. Rhubarb leaves contain oxalic acid, a chemical compound found in bleach, metal cleaners and anti-rust products. The leaves also contain anthraquinone glycosides. Eating the leaves can lead to a burning sensation in the mouth and throat, nausea and vomiting, gastric pain, shock, convulsions and even death.
Although rhubarb sold at the store genrally has most of the leaves removed, be careful if you grow it at home; although using every part of a vegetable is generally great ... in this case, the shock, convulsions and death aren't quite worth it.
7. Tomatoes and potatoes
The leaves and stems of both tomatoes and potatoes, members of the nightshade family, contain a toxic alkaloid called solanine. In potatoes, it is particularly concentrated when the spud starts to sprout and when the eyes and flesh turn green. Potatoes have higher concentrations than tomatoes- and a report from the University of New Mexico notes that wild potatoes in the Andes can be more than double that of cultivated potatoes.
But even so, a 100-pound person would need to eat 16 ounces of a fully green potato before solanine poisoning would occur. If you happen to have a taste for green potatoes, keep an eye out for excessive salivation, diarrhea, slowed pulse, reduced blood pressure and respirations, and cardiac arrest.
No list of poisonous foods would be complete without mention of mushrooms, and specifically, Amanita phalloides, the deadly (and dastardly delicious) "death cap" mushroom. Responsible for a multitude of mushroom poisonings , along with its cousin, Amanita ocreata, better known as the "destroying angel."
Our fascination with funghi goes way back and we continue to poison ourselves with various members of the mushroom family. Why? Because they are amazing to eat, while at the same time, it's hard to differentiate between those that are good and those that are deadly. If you have a fondness for foraging, take Matt Hickman's advice: be totally neurotic.