So then, why is the almond the only type of prunus pit we eat? It’s not because cherry, apricot and peach pits are hard to crack and chew (though they are). It’s because the pits of most prunus drupes contain a chemical known as amygdalin, a member of a family of compounds known as cyanogenetic glucosides. As the name implies, cyanogenetic glucosides are sugars, but with an important difference: they have molecules of cyanide attached to them. Eat them and the body’s digestive enzymes go to work, breaking them down into simple sugars plus hydrogen cyanide, a deadly poison.
Just how much poisonous cyanide is there in a typical peach pit? Not very much. Certainly not enough to kill a human, but then a human would have to go well out of his or her way to crack open a stone like that. If you’ve ever accidentally bitten down on one while eating a peach, you know the things are darn near impenetrable. That’s by design, since drupe pits have evolved to be tough enough to travel the length of a large mammal’s digestive track and emerge at the far end unscathed, in a pile of dung far away from their parent tree, ready to germinate.
So why the cyanide? Call it an insurance policy against an overzealous herbivore. The implicit message of the poison pit is: swallow me if you like but don’t chew me, I’ve got places to go, and you’re just my ride.
But hang on, Joe. You said that almonds are drupe pits and we eat them, don’t they have poison in them as well? In fact almonds don’t have any amygdalin in them, or if they do, it’s only present in trace amounts. Certainly not enough to worry about.