Kidney beans are only as safe as you cook them. Before I get into the whys of the safety of kidney beans I'll just give a quick overview on proper cooking of these beans. The first thing to do with dried kidney beans is to soak them for a few hours. Drain the water from the beans. Boil the beans in fresh water for at least 10 minutes.
Canned kidney beans are perfectly safe. You don't have to worry about eating them. They should've been properly cooked before being canned.
The problem is with fresh or dried kidney beans which have not been boiled for at least 10 minutes. For some reason the plant (probably as a protective device for the seeds) produces an insecticide which is contained in beans in general and red kidney beans in particular.
Most beans contain very little of this toxin and it should not be something to worry about. Kidney beans, especially red kidney beans, contain more of this insecticide. The symptoms of red kidney bean poisoning are intense vomiting and diarrhea. People normally recover fine on their own but because it is food poisoning not food discomfort a doctor should be called if you suspect you may have under cooked your beans and poisoned yourself.
When these beans are undercooked they actually become more poisonous than if they are eaten raw. So remember 10 minutes boiling. Do not cook kidney beans in a slow cooker or crock pot unless you make sure that they will hit the boiling point. Boil them first or sit there and watch that pot till it boils. Unless you want to spend a pleasant afternoon trying to figure out which end needs the toilet the worst.
The actual name of the toxin is phytohemagglutinin and if you want to know more about itâ€¦good luck getting all those letter in the right order in Google because that's all the details I plan to share.
The important thing is 10 minutes boiling = non poisonous kidney beans. Personally I'll stick with the canned stuff. Cheap and easy just like â€¦ I like my beans.