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, and especially when people have protein in their diet, 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.