Cooked properly, red kidney beans can be part of a healthy diet. However, they should never been eaten raw or only partially cooked. They contain a naturally occurring toxin called Phytohaemagglutinin. Boiling the beans for 10 minutes deactivates the toxin. It is also recommended to soak them overnight before cooking. [source] Never cook kidney beans in a slow cooker, as they are only simmered at low temperatures and not boiled.