Where do Cashew Nuts come from and Why are Raw Cashew Nuts Poisonous?

The succulent “fruits” of the tropical cashew tree Anacardium occidentale, often called cashew apples, are about the size and shape of a pear. They are not only edible but quite delicious.

Since they are highly perishable, however, you won’t find them very far from the trees. I was lucky enough to taste them when I lived in Venezuela, where they grow and are called merey.

Attached to the “apple” at its lower end is the kidney-shaped nut (which, botanically speaking, is actually the fruit), encased in a double shell. Between the shells is a gummy phenolic resin containing the corrosive and poisonous chemicals anacardic acid and cardol, among others. If eaten, this resin would actually cause blisters in the mouth.

Obviously, the poisons must be removed before the nuts are safe to eat. This is accomplished by roasting the unshelled nuts in hot oil, which does two things: it drives off the resins, and it makes the shells brittle enough to crack by hand with a mallet, a method that continues to survive into the twenty-first century. Both the shells and the corrosive chemicals are long gone before you ever see them in the store.

The nuts are perfectly edible at this stage, and are sold as “raw cashews” in spite of the fact that they have already been cooked at 365 to 375°F (185 to 190°C). Commercially packaged cashews are usually roasted again at 325°F (163°C); this roasting softens them and enhances their color and buttery flavor.

Those raw-foods-only restaurants and other raw-food devotees who insist that food must never be allowed to exceed 118°F (48°C) make frequent use of “raw” cashew nuts and “raw” cashew butter in their creations. Either they’re kidding themselves or they don’t know that their nuts were roasted at a much higher temperature long before they saw them.