What it is
Legumes ship with their own security: lectins and phytic acid, the seed's defense against being eaten.
Why your biology objects
Lectins (phytohaemagglutinin) bind the gut lining and are genuinely toxic raw — raw kidney beans will make you sick; phytic acid chelates zinc and iron, blocking absorption. Boiling destroys the lectins and soaking stands down much of the phytate, which is exactly why every bean culture on earth converged on the pot. The processing *is* part of the ingredient.