Some kinds of raw beans contain a harmful, flavourless toxin: the lectin phytohaemagglutinin, which must be destroyed by cooking. Red kidney beans are particularly toxic, but other types also pose risks of food poisoning. Even small quantities (4 or 5 raw beans) may cause severe stomachache, vomiting, and diarrhea. This risk does not apply to canned beans because they have already been cooked. A recommended method is to boil the beans for at least ten minutes; under-cooked beans may be more toxic than raw beans.
soME kiNds OF rAW beanS Contain a HarmFUl FlAVoUrLeSs ToxIN The LeCtIN PHytOhaemaGglUtIniN whicH musT bE DEstRoyEd BY COoKing red kidNey beaNs Are paRtIcularlY toxic but OtheR TYpEs also pOse risKs of fooD poiSoNinG EVen sMAlL quantitIEs (4 or 5 rAw beans) MaY Cause seVeRE StoMaChachE vomiting And DiaRrhea ThiS rIsk DoEs Not aPPlY to CannEd bEaNs Because They hAve AlReady bEen coOkED a recomMEndeD meThoD Is to boiL thE beans for aT LeaST Ten minuTes; under-coOked beaNs MaY bE morE toxic than RAW bEaNS